Petrographical and Mineralogical Characteristics of Magmatic Rocks in the Northwestern Siberian Traps Province, Kulyumber River Valley. Part I: Rocks of the Khalil and Kaya Sites

Abstract

The origin of the Siberian Traps province has been under discussion for the last three decades. Up to now, there is no real model of its formation in a good agreement with geological data on the magmatic evolution at P–T boundary in Eastern Siberia. Modern geochemical data on magmatic rocks around the province is a key to reconstructing magmatic development in time and space. Such data have been obtained for the Norilsk and Meimecha–Kotuy and not for other parts of the Siberian province. For the first time, we studied the geochemistry and mineralogy of magmatic rocks at the Kulyumber river valley, located in the intersection of the Tunguska syneclise and Norilsk–Igarka zone in the NW Siberian platform. In this article, we present data from the Khalil and Kaya sites of this area belonging to the Syverminsky, Gudchikhinsky, Khakanchansky and Nadezhdinsky formations. Their mineralogical and geochemical features (including Sr, Nd and Pb isotope data) are similar to the same formations in the Norilsk area, while the rocks belonging to the Gudchikhinsky formation show differences. The Syverminsky tuffs are also described for the first time. The intrusive rocks are attributed to four intrusive complexes, i.e., Ergalakhsky, Kureysky, Katangsky and Norilsk. The Ergalakhsky complex comprises trachydolerites similar to the trachydolerites of the Norilsk area. The rocks of the Norilsk complex at the Khalil site differ from the rocks of the same complex at the Norilsk area by the (U/Nb)n = 1.8, (La/Yb)n = 2.1 in comparison with 3.7 and 2.3 of the rocks of the Norilsk 1 intrusion. The intrusions of the Kureysky complex are more differentiated than those of the Katangsky intrusions but show comparable TiO₂ and trace elements distribution. Thus, the magmatism of the Kulyumber area is characterized by features matching those of the Tunguska syneclise and Norilsk area, i.e., suggesting rift and platform regimes.

1. Introduction

The origin of large igneous provinces (LIPs) has been under discussion for the last three decades [1,2,3,4,5]. The Siberian Traps province—the largest continental flood basalt province on Earth—is attracting geologists by the huge volume of magmatic rocks (1.5 M km³, [6,7]), occurrence of extra-large PGE-Cu-Ni deposits [8,9,10,11,12,13,14,15,16,17] and a possible link with the Permian–Triassic mass extinction [18,19,20]. Despite continuous debates on its genesis [21,22,23,24,25,26], the problem of the Siberian Traps origin is far from its satisfactory explanation. Continued detailed study of magmatic rocks within the province is a key to understanding of its origin and reconstructing of its magmatic evolution in space and time around the Siberian province.

The great scale of the province and many remote areas in Eastern Siberia are the main reasons for incomplete information on this great volume of magmatic rocks. Modern geochemical studies have so far been conducted only for the Norilsk and Meimecha–Kotuy regions, which comprise PGE-Cu-Ni magmatic deposits and high alkaline rocks, respectively [27,28]. In these areas, major, trace and isotopic data are a valuable for lavas [29,30,31,32,33,34,35,36,37]. Data on intrusive rocks are more restricted in comparison with basalts and refer mainly to the Norilsk ore-bearing intrusions [14,38,39,40,41,42,43,44,45]. Other parts of the province have been studied only in a reconnaissance way [46,47]—or not examined at all.

This study is focused on the Kulyumber area located in the middle part of the Kulyumber river valley which represents one of the least studied areas of the province (Figure 1). It is located between the Tunguska syncline and Norilsk–Igarka zone [48,49,50] and thus it provides information on the magmatic events within both structures at the Permian–Triassic boundary (250 ± 0.3 Ma; [51]). Within this territory effusive rocks and numerous intrusive bodies were found during the geological mapping. The volcanic rocks were subdivided into five formations according with the formations of the lower part of the tuff-lava sequence in the Norilsk area, i.e., Syverminsky, Gudchikhinsky, Khakanchansky, Tuklonsky and Nadezhdinsky formations [14]. Intrusions have been attributed to eight intrusive complexes located both in the Norilsk district and in Tunguska syneclise [14]. This division is doubtful, since it is based on the inner structure of intrusive bodies and structural and textural features of rocks.

The purpose of this work is to study the mineral composition and geochemical characteristics of igneous rocks and compare them with the rocks of the Norilsk area and Tunguska syneclise. As has been shown in [14,17,31,32,33], both OIB (Oceanic Island Basalts) and WPB (Within-Plate Basalts) occur in the Norilsk area and were formed in a rift system and during a platform magmatism. For the Tunguska syneclise only platform magmatism is described. Magmatism of the Norilsk area occurs mainly within the Yenisey–Khatangsky trough (YKT). The Kulyumber river valley is not considered as a part of the Norilsk and YKT but it is involved in the rift zone. There are many questions that are not answered about the formation of this region. What types of igneous rocks occur in the Kulumbe River valley? Are there any variations in the compositions of rocks along the strike of the tectonic structure from the north to the south? Or are they a constant homogeneous in composition? What types of primary magmas formed the igneous rocks of the Kulyumber river valley? How does a transition from rift magmatism to a platform one happen—abruptly or gradually? To answer these questions, we must collect information first of all on mineralogy and geochemistry of igneous rocks of this area.

Furthermore, the Kulyumber area is considered as a priority region for the discovery of new deposits because the geologists of the company, "Norilskgeology” have found the disseminated and massive sulfide ore in gabbro within this area, in contrast to other regions of the Siberian platform where only poor mineralization was detected. Does the rift zone from the Norilsk area and the Kulyumber area show a consistent trend of mineralization?

2. Tectonic Structure

The studied area is located in NW Eastern Siberia, 150 km to the south of the Norilsk ore district. The tectonic structure of the territories is complex due to their occurrence within two different structural blocks. The eastern part belongs to the Siberian craton consisting of a crystalline basement and a platform cover. The western part has a more complex structure due to the depth of the basement and a huge volume of sediments and intrusions within it.

First of all, we have performed a new geophysical map of the crystalline basement of north-western part of the Siberian platform where Kulyumber area is located (Figure 2). The initial data were the results of 1:200000 scale gravimetric and 1:100000 scale aeromagnetic mapping performed at constant barometric altitudes (700 m and 2400 m), as well as a digital landscape model GTOP030. The geophysical fields were converted to a horizontal plane with a height of 2400 m by approximation by equivalent sources [52]. This allowed to reduce the influence of the relief of the earth’s surface and local inhomogeneities in the upper part of the geological section. The measured values of the geomagnetic field intensity T were converted into the vertical component of the anomalous magnetic field ΔZ, which has a more distinct relationship with the anomaly forming objects. The network of points for digital models of fields and terrain used in processing is 2 × 2 km.

Figure 2 shows a submeridional band of positive values of the gravitational field stretched along the Yenisey River, about 100 km wide, bordering the ancient craton and extending beyond the southern frame of the area. This zone is probably a fragment of an ancient rift structure with increased mobility and permeability for magma, saturated with basic-ultrabasic magmatic rocks. The gravity anomaly has the form of a flattened funnel, elongated in the meridional (N–S) direction, with a "vent" (or "main supply channel") going into the upper mantle, which is located beneath the in area of Igarka city. The zone is characterized by low values of the magnetic field due to the presence of iron only in silicate form.

Of particular interest are the sub-latitudinal zone of low magnetic field values and slightly elevated values of the gravity field, covering the basins of the Kulyumber river and stretching to the upper flows of the Kureyka river (to the east from Snezhnogorsk city, Figure 2). According to geophysical data this zone is close to the Norilsk–Igarka zone and corresponds to the sub-latitude Dyupkun branch of the Norilsk–Igarka rift system [49,50] isolated by Malich [48]. Based on magnetic and gravity data we identified another rift structure, i.e., Tunguska branch, to east from Turukhansk City. It is weakly manifested in geophysical fields.

According to the morphology of geophysical fields there is a series of lineaments with north-western and sub-latitudinal directions, presumably corresponding to deep faults. The junctions of these faults are the most permeable magmas areas of the earth’s crust; they can be considered as regional criteria for massifs with platinum–copper–nickel mineralization. One of the largest junctions is located in the Norilsk district, the other one is fixed in the basin of the Kulyumber river.

The presence of local (20–40 km across) magnetic inhomogeneities modeled at 5 to 15 km deep, in some cases spatially combined with density inhomogeneities, was also established within the territory under consideration. Their geological nature has not yet been clearly defined.

3. Brief Geology of the Area

The local structures of the studied area are the Nirungdinsky Trough and the Mogen-Khalil Anticline (Figure 3) [53,54]. Sedimentary rocks are exposed on the surface and they are represented by Devonian carbonate–terrigenous rocks and Lower Carboniferous–Middle Permian (C₂–P₂) sediments comprising sandstones and coal. Early Triassic magmatic rocks belong to the Siberian flood basalts province. Volcanic rocks were subdivided into several formations and constitute the lower part of the volcanic sequence of the Norilsk area [53,55], i.e., Syverminsky, Gudchikhinsky, Khakanchansky, Tuklonsky and Nadezhdinsky formations.

Intrusive bodies occupy up to 30% of the volume of sedimentary rocks. They were attributed to several intrusive complexes based on the texture and structure of the rocks, petrography and a few whole-rock geochemical analyses. Although analytical data are insufficient, they were considered similar to the intrusive complexes typical of the Tunguska syneclise (Katangsky), the Norilsk area (Ergalakhsky, Norilsk) and local Kureysky complex.

Intrusions are represented by sill-like bodies (with a thickness of 5–6 to 50 m and a length of up to 10–15 km), located mostly in sedimentary rocks. Rare dikes also cut the volcanic rocks. The Imangdinsky–Letninsky and Khalilsky faults (Figure 3) controlled intrusion of magmas.

Intrusive bodies consist of olivine gabbro-dolerites or gabbro and leucogabbro. High-magnesian rocks occur in differentiated intrusions as distinct horizons and do not form separate bodies.

The authors have obtained the first modern geochemical data on magmatic rocks of this area including their isotopic characteristics. The results allowed subdividing intrusive rocks more correctly than it was done previously.

4. Objects and Methods

The authors studied igneous rocks in three sites within the Kulyumber river valley, i.e., the Khalil, Kaya and Kulyumber (Figure 3). Here we discuss the magmatic rocks of the two first sites (Figure 3, Figure 4 and Figure 5). Data on the rocks from the Kulyumber site will be discussed in the second part of the article. The studied rocks were compared with the rocks of the Norilsk district and volcanic rocks of the Lama Lake area (Figure 1), which has a similar tectonic position between the Tunguska syneclise and the Norilsk–Igarka paleorift zone. The total list includes 57 samples (Tables 2 and 5).

Major and trace element concentrations in the rocks were determined using X-ray fluorescence (XRF) at the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of Russian Academy of Science (IGEM RAS), Moscow, Russia (analyst A.I. Yakushev), and inductively coupled plasma mass spectrometry (ICP-MS) at Institute of Microelectronics Technology and High Purity Materials RAS (IMT RAS), Chernogolovka Russia (analyst V.K. Karandashev). The latter method has been described earlier [56].

Sr, Nd and Pb isotopes were studied in representative samples from volcanic rocks at A.P. Karpinsky Russian Geological Research Institute (VSEGEI), St. Petersburg, Russia (analyst B.V. Belyatsky). Chemical separation of elements was carried out by chromatographic method on ion exchange columns according to the method described earlier [57] and the procedure of isotopes measurement was described in [57].

Compositions of rock-forming minerals were analyzed using an electron microprobe CAMECA SX 100 at Vernadsky Institute of Geochemistry and Analytical Chemistry of RAS (analyst N.N. Kononkova) and at Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of RAS with the aid JEOL JXA 8200 (analyst V. Taskaev) at a 30-nA beam and 20-kV accelerating voltage. The count time was 20 s, probe diameter −1 micron. Standard samples are San Carlos (olivine-Fe_Kα, Mg_Kα, Ni_Kα), natural minerals sanidine (Si_Kα, Al_Kα, K_Kα), spessartin (Mn_Kα), anorthite (Ca_Kα), albite (NaKα), chromite (Cr_Kα), F-phlogopite (F_Kα), ilmenite (Ti_Kα), (in brackets-analytical line used). Element concentrations were calculated using the ZAF correction method.

5. Results

5.1. Volcanic Rocks

Volcanic rocks (mainly lavas and tuffs) occur in the eastern part of the area, within the Nirungdinsky trough (Figure 3). Five formations were recognized: Syverminsky, Gudchikhinsky, Khakanchansky, Tuklonsky and Nadezhdinsky. We studied in detail the structure and composition of the lower part of the lavas sequence in the Khalil site, Section 1 (Figure 4) and compare it with the lower part of the volcanic section in the eastern Norilsk area, Section 2, Lake Lama. Several samples were also analyzed at the Kaya site (Figure 5).

5.1.1. Structure of Tuff-Lava Sequence and Petrography of Volcanic Rocks

The volcanic Section 1 (Figure 4, points X-20–X-27) in the Khalil site (Figure 6) begins with the Syverminsky formation which consists of eight lava flows (total thickness of 140 m). The flows have an average thickness of 10–15 m. They are overlain by olivine basalts of the Gudchikhinsky formation. Two sills cut these basalts.

The Syverminsky formation comprises middle-size grained aphyric lavas and tuffs. Poikilophytic varieties dominate in the lower part of the Syverminsky formation while its upper part mostly consists of tholeiitic basalts (Figure 7a,b). Poikilophytic structure characterizes the three lower flows of the section where large clinopyroxene oikocrysts (0.5 mm) comprise elongated plagioclase chadacrysts. Tholeiitic basalts consist of plagioclase (40–55 vol.%), clinopyroxene (15–40 vol.%), volcanic glass (5–15 vol.%), Fe-Ti oxides (1–3 vol.%). Sometimes they are enriched in titanite (Figure 8a,d). Glass is devitrified (Figure 8a,b) and altered (opacitated) and pallagonite occurs in groundmass (Figure 7a and Figure 8a). Secondary minerals are chlorite, amphibole. Margins of flows are represented by fine-grained amygdaloidal basalts (Figure 7b). Plagioclase comprises 52–70 mol% An; clinopyroxene composition varies in narrow range (Wo_36–38En_46–47Fs_15–16); this mineral contains up to, in wt.%, TiO₂:0.52, MnO:0.31, Al₂O₃:3.63, Cr:0.25 (

Table 1. Chemical composition of rock-forming minerals from volcanic rocks of the Khalil site, wt.%.

No.	Sample	SiO2	TiO2	Al2O3	FeO	MnO	MgO	CaO	Na2O	K2O	Total	Mineral
1	X-20	53.98	bdl	27.77	0.89	bdl	0.24	11.70	4.62	0.31	99.51	Pl
2	X-20	55.62	bdl	26.84	0.95	bdl	0.10	10.57	5.32	0.41	99.80	Pl
3	X-20	50.83	bdl	29.59	0.61	bdl	0.36	14.34	3.31	0.12	99.17	Pl
4	X-20	51.74	0.40	3.63	6.63	0.14	16.16	20.21	0.23	bdl	99.36	Cpx
5	X-20	51.43	0.52	1.62	12.68	0.31	14.48	18.04	0.22	bdl	99.35	Cpx
6	X-20	49.30	0.20	6.04	18.15	0.32	14.25	8.98	0.38	0.09	97.71	Glass
7	X-20	30.77	37.38	2.01	0.87	0.02	0.07	28.95	0.03	0.00	100.10	Titanite
8	X-26	48.09	0.67	4.62	18.12	0.20	13.96	10.87	1.20	0.21	98.20	Am
9	X-26	49.47	1.08	4.55	16.33	0.24	12.25	12.04	0.82	0.18	97.01	Am
10	X-26	63.14	0.04	19.81	0.28	0.01	0.06	0.66	0.64	13.87	98.51	Kps
11	X-26	58.31	0.07	25.61	0.78	0.02	0.07	8.06	6.23	0.52	99.66	Pl
12	X-26	67.58	0.02	20.82	0.31	0.01	0.01	0.84	9.81	0.10	99.50	Pl
13	X-26	57.06	0.15	27.17	0.94	0.02	0.23	7.33	4.82	1.87	99.59	Pl
14	X-26	67.57	0.04	20.62	0.22	0.02	0.00	1.00	9.97	0.15	99.57	Pl
15	X-26	54.06	bdl	27.48	1.07	bdl	0.36	11.41	4.78	0.27	99.42	Pl
16	X-10	0.30	45.75	0.10	48.45	3.35	0.05	0.05	0.01	0.01	98.06	Ilm
17	X-10	61.88	0.00	25.55	0.30	0.04	0.06	2.31	5.52	3.65	99.30	Pl
18	X-10	48.26	0.04	26.79	2.31	0.08	0.43	13.69	1.51	3.66	96.76	Pl
19	X-10	52.32	0.08	28.73	0.47	0.00	0.16	12.84	3.79	0.33	98.71	Pl
20	X-10	50.71	0.39	3.41	17.14	0.25	12.14	12.37	0.34	0.17	97.69	Px
21	X-10	39.05	0.79	11.52	22.21	0.18	14.54	0.71	0.03	4.83	93.86	Am
22	X-10	54.07	0.05	28.16	0.56	0.03	0.15	11.87	4.18	0.36	99.42	Am
23	X-10	51.93	0.32	2.75	20.29	0.42	10.69	12.77	0.34	0.12	99.61	Cpx
24	X-37	62.46	2.18	18.62	0.20	0.00	0.03	2.57	8.63	0.32	95.01	Glass
25	X-37	29.33	0.02	18.73	25.08	0.33	16.70	0.15	0.02	0.03	90.48	Glass
26	X-37	28.19	0.01	17.66	25.41	0.32	16.25	0.11	0.01	0.02	88.10	Glass
27	X-37	4.42	0.00	0.60	74.69	0.00	0.27	0.57	0.04	0.39	81.04	Mag
28	X-37	64.01	0.03	19.54	0.10	0.00	0.01	0.03	0.34	15.22	99.28	Kps
29	Х-27	50.30	1.08	2.00	10.09	0.24	14.99	19.41	0.31	0.00	98.41	Cpx
30	Х-27	50.39	1.13	1.93	10.59	0.29	14.96	19.14	0.35	0.01	98.79	Cpx
31	Х-27	51.33	0.69	1.97	7.70	0.20	15.94	21.49	0.25	0.02	99.58	Cpx
32	Х-27	51.58	0.98	1.99	9.20	0.21	15.27	19.76	0.27	0.00	99.25	Cpx
33	Х-27	50.82	0.15	2.81	23.40	0.65	15.63	2.93	0.54	0.12	97.04	Opx
34	Х-27	51.22	0.08	30.36	0.70	0.02	0.10	13.67	2.90	0.92	99.96	Pl
35	Х-27	53.96	0.14	29.43	0.72	0.00	0.09	10.34	4.99	0.42	100.07	Pl
36	Х-27	0.29	47.42	0.05	48.12	1.93	0.06	0.08	0.00	0.01	97.95	Ilm
37	Х-27	4.42	0.00	0.60	74.69	0.00	0.27	0.57	0.04	0.39	80.98	Mag
38	Х-27	49.14	0.08	27.02	0.78	0.00	0.06	11.37	4.25	0.37	93.06	Glass
39	Х-27	64.01	0.03	18.54	0.10	0.00	0.01	0.03	0.34	15.22	98.28	Kps
40	Х-27	38.36	bdl	bdl	21.57	0.28	40.21	0.23	bdl	bdl	100.65	Ol
41	Х-27	38.25	bdl	bdl	22.44	0.27	38.84	0.24	bdl	bdl	100.02	Ol
42	Х-0	65.95	0.00	18.34	0.00	0.01	0.01	0.12	0.74	14.55	99.73	Kps

Note: Analysis Nos 4, 5, 8, 32 containing Cr₂O₃ 0.15, 0.21, 0.25, 0.77 consequently; analyses No 7—0.15 Cl; analysis Nos 40, 41—0.31 and 0.33 Ni. Formations, No: 1–28—Syverminsky, 29–40—Gudchikhinsky, 41—Khakanchansky. Minerals: Ol—olivine, Kps—potassium feldspar, Mag—magnetite, Opx—orthopyroxene, Cpx—clinopyroxene, Ilm—ilmenite, Pl—plagioclase, Am—amphibole; bdl—below detection limit.

).

The maximum thickness of pyroclastic rocks was found on the eastern side of the Khalil river valley. They occur as tuff horizons (first meters thick) or form extrusions consisting of tuff-lavas breccias. A paleovolcano was found in the riverbed of the left tributary of r. Khalil (Figure 4). Its diameter is 300–350 m and its height ranges from 20 to 30 m. It consists of agglomerate tuffs and tuff breccias with fragments of basalts and sedimentary rocks from 5–6 cm to 0.5–0.8 m. Vitro–lithoclastic tuff (Figure 7c,d and Figure 8e) consists of glass (40%–60%), pyroxene, plagioclase, potassium feldspar and calcite.

The Gudchikhinsky volcanic rocks are represented by olivine-bearing basalts with aphyric texture (Figure 7c,d) in contrary to the similar rocks located in the Norilsk area where they are usually porphyric (with plagioclase and olivine phenocrysts). They are fine- or middle-size grained with vitrophyric and micro-ophitic structure. Plagioclase (0.2–0.3 mm in length; 40–60 vol.%; An₆₀) and clinopyroxene (0.1 mm; 25–40 vol.%; Mg# = 70) are the main rock-forming minerals, there is minor olivine (0.05–0.1 mm; Fo_70–73) 2–3 vol.% and glass–1%–2%. Opaque minerals are Cr-magnetite, ilmenite. Secondary minerals are chlorite, amphibole and prehnite. Compositions of rock-forming minerals are given in Table 1.

We compared the tuff-lava sequence of Section 1 (Figure 6a) with the lower sequence of volcanic rocks of the north coast of Lake Lama located in the eastern Norilsk area (Section 2). Early we payed particular attention to the middle part of the volcanic sequence, i.e., formations overlapping the Ivakinsky formation in the Khalil area should be underlined (Figure 6b). The Syverminsky basalts lie on the sedimentary rocks of the Tunguska Group (C₂–P₂) and are overlain by basalts of the Gudchikhinsky formation everywhere around the Kulyumber area. The thickness of the Syverminsky formation in both sections is similar (140 and 160 m, respectively). The Lake Lama section consists of 9 flows of tholeiitic basalts overlapped by two flows of poikilophytic basalts. The Gudchikhinsky formation in the Lama Lake area consists of picrites [36] or picritic basalts attributed to the middle subformation while in the Khalil area it is represented by olivine basalts (lower subformation).

The studied volcanic rocks of the Kaya site coming from the bottom of the tuff-lava section. They belong to the Syverminsky formation and are represented by tholeiitic and poikilophytic basalts similar to the rocks of Section 1.

5.1.2. Geochemistry of Volcanic Rocks

Major elements. Chemical compositions of the volcanic rocks from the Khalil and Kaya sites of the Kulyumber area and Norilsk area are given in

Table 2. Composition of the volcanic rocks from the Khalil and Kaya sites and Norilsk area.

No	1	2	3	4	5	6	7	8
Sample, No	X-3-2	X-3-3	X-10	X-20	Х-21/3	X-22	X-24	X-26
SiO2	51.26	53.84	51.34	49.74	53.23	52.31	47.46	48.64
TiO2	1.55	1.74	1.67	1.52	1.55	1.63	1.79	1.23
Al2O3	15.03	15.22	14.63	14.74	14.22	14.47	14.09	14.94
Fe2O3	10.89	9.86	11.45	10.94	9.68	10.38	14.44	11.23
MnO	0.22	0.07	0.23	0.20	0.12	0.21	0.17	0.14
MgO	3.95	3.43	5.47	6.30	5.88	5.16	4.94	6.89
CaO	5.46	3.23	7.21	4.93	4.70	7.32	9.46	7.48
Na2O	6.46	7.16	3.79	3.03	6.10	3.78	3.94	3.50
K2O	0.07	0.09	1.66	3.28	0.12	1.81	1.17	1.78
P2O5	0.23	0.22	0.23	0.21	0.21	0.23	0.29	0.13
LOI	4.65	4.98	2.23	4.74	3.92	2.41	3.63	3.89
Li	22.77	17.51	22.71	n/a	29.91	35.7	86.54	34.44
Rb	120	103	67.0	n/a	2.59	74.2	117	45.5
Sr	508	712	652	n/a	253	659	754	1395
Y	27.0	32.1	29.5	n/a	32.6	27.8	28.4	18.1
Cs	0.64	0.09	2.02	n/a	0.06	0.96	0.29	0.45
Ba	234	312	404	n/a	14	827	759	422
La	24.0	29.6	22.3	n/a	67.8	21.2	19.7	21.1
Ce	37.4	68.2	47.4	n/a	99.3	46.5	46.0	37.1
Pr	4.81	9.82	5.62	n/a	8.80	5.10	5.90	4.47
Nd	21.1	39.7	21.9	n/a	33.5	21.5	20.3	15.2
Sm	4.94	7.85	5.68	n/a	6.65	5.06	5.54	3.68
Eu	1.30	2.27	1.66	n/a	1.36	1.32	1.29	1.54
Gd	4.71	6.59	4.64	n/a	6.09	4.97	4.76	3.41
Tb	0.77	0.99	0.85	n/a	0.92	0.84	0.80	0.55
Dy	4.67	5.93	5.30	n/a	5.51	5.15	4.97	3.50
Ho	0.90	1.13	1.04	n/a	1.05	0.98	1.03	0.68
Er	2.62	3.13	2.88	n/a	3.04	2.91	2.90	1.74
Tm	0.37	0.42	0.40	n/a	0.42	0.39	0.37	0.24
Yb	2.54	2.92	2.41	n/a	2.65	2.64	2.64	1.59
Lu	0.35	0.40	0.37	n/a	0.38	0.39	0.36	0.23
Pb	3.29	18.24	5.52	n/a	0.30	1.28	4.71	4.20
Th	4.73	5.22	4.80	n/a	4.48	5.09	5.25	2.80
U	1.32	1.87	1.25	n/a	1.23	1.46	1.38	0.71
Sc	21.6	21.6	29.9	n/a	21.2	24.1	28.7	28.6
Ti	9292	10431	11912	n/a	9292	n/a	11264	8358
V	168	149	187	n/a	159	171	176	207
Cr	183	188	219	n/a	204	206	219	305
Co	25.3	7.6	33.9	n/a	24.9	26.3	18.4	53.9
Ni	30.0	19.0	56.5	n/a	54.3	56.8	56.9	105.6
Cu	28.3	26.5	125	n/a	17.4	9.21	17.5	113
Zn	137	53.2	150	n/a	38.0	38.0	30.6	54.8
Ga	20.0	23.1	n/a	n/a	18.5	18.4	n/a	n/a
Zr	212	231	251	n/a	209	208	255	158
Nb	16.1	18.2	17.6	n/a	15.8	19.2	18.6	8.8
Hf	4.61	5.15	5.84	n/a	4.41	5.46	5.96	3.55
Ta	1.01	1.10	1.26	n/a	1.03	1.16	1.31	0.53
No	9	10	11	12	13	14	15	16	17
Sample, No	X-27	Х-28	3.20/1	3.21/1	3.23/1	Х-37	X-0	4270	4270/4
SiO2	49.09	51.22	52.69	50.15	47.45	50.93	54.93	45.14	52.54
TiO2	1.20	1.56	1.56	1.40	1.35	1.03	1.14	3.91	2.44
Al2O3	15.50	14.67	14.22	13.96	15.55	13.43	14.64	13.46	13.99
Fe2O3	10.57	11.56	9.79	13.60	11.63	10.23	9.83	13.23	11.62
MnO	0.18	0.12	0.23	0.17	0.24	0.13	0.13	0.21	0.19
MgO	7.96	5.72	5.62	6.10	5.80	5.89	5.56	3.58	3.37
CaO	8.88	4.12	6.37	5.55	11.43	5.91	2.84	10.54	7.50
Na2O	2.80	3.55	3.18	2.37	2.68	2.77	2.71	2.35	3.12
K2O	1.33	2.83	1.55	0.40	0.16	1.40	2.27	1.95	1.85
P2O5	0.13	0.21	0.22	0.19	0.14	0.15	0.18	0.12	0.71
LOI	2.12	4.08	4.29	5.83	3.43	7.72	5.61	3.87	2.32
Li	19.77	34.13	13.54	17.20	21.25	41.89	36.60	20.31	8.61
Be	0.57	1.80	0.55	0.34	0.08	1.37	n/a	2.48	2.25
Rb	29	101	8.12	3.33	39	36	58	31	19
Sr	490	439	401	380	346	168	173	503	409
Y	15.1	26.6	20.2	26.1	26.0	21.0	24.9	46.9	35.9
Cs	1.14	0.25	n/a	n/a	n/a	0.28	0.32	0.78	1.90
Ba	323	337	230	292	585	315	989	986	848
La	12.2	20.7	21.2	22.3	35.2	20.4	26.5	43.2	26.9
Ce	26.7	46.5	42.2	48.9	68.4	44.6	56.2	101.6	69.1
Pr	3.3	5.42	4.59	6.03	7.53	5.05	6.76	13.02	9.29
Nd	14.8	23.9	17.3	25.2	28.9	21.2	22.2	52.6	40.0
Sm	3.49	5.64	4.19	6.13	6.38	4.41	5.27	10.51	8.81
Eu	1.25	1.36	1.58	1.82	1.71	1.25	1.39	2.80	2.66
Gd	3.35	5.27	3.91	5.71	5.93	3.94	4.23	9.59	8.17
Tb	0.52	0.80	0.64	0.90	0.88	0.59	0.80	1.50	1.34
Dy	2.94	4.79	3.89	5.05	5.02	3.55	4.52	8.82	7.93
Ho	0.57	0.90	0.77	1.00	0.99	0.66	0.90	1.80	1.60
Er	1.43	2.65	2.03	2.69	2.65	1.88	2.44	4.76	4.30
Tm	0.22	0.35	0.29	0.37	0.38	0.26	0.38	0.70	0.64
Yb	1.38	2.33	1.76	2.40	2.54	1.72	2.30	4.23	3.84
Lu	0.20	0.34	0.25	0.35	0.36	0.25	0.35	0.63	0.56
Pb	2.15	0.40	4.18	2.07	3.87	1.41	10.10	8.98	11.20
Th	0.79	4.11	5.22	2.90	4.12	3.50	5.53	3.42	1.43
U	0.2	1.01	1.41	0.76	1.07	0.91	1.35	2.07	1.37
Sc	26	22.1	12.1	24.0	21.7	21.8	32.4	18.9	14.2
Ti	7194	9352	5904	10316	8809	6175	8041	22308	6840
V	194	175	123	190	161	184	175	175	125
Cr	312	228	1736	158	212	272	226	49	160
Co	43.3	26.4	14.3	30.3	39.7	36.4	31.1	34.2	27.4
Ni	129	60.6	85.3	48.0	80.2	77.4	60.9	25.9	24.9
Cu	59.4	26.5	98.6	31.1	55.5	66.5	77.8	43.4	22.7
Zn	56	31.1	bdl	bdl	118.1	39.8	355	183	140
Ga	17.1	20.1	n/a	n/a	n/a	18.70	n/a	23.79	24.15
Zr	89.1	191	198	187	90	133	201	399	401
Nb	8.19	16.7	15.1	12.4	14.3	10.1	13.8	40.3	11.5
Hf	1.94	4.07	3.18	4.51	4.84	2.96	5.22	8.45	9.14
Ta	0.38	1.02	0.82	0.90	0.96	0.61	0.83	2.51	0.59
No	18	19	20	21	22	23	24	25	26
Sample,No	4270/5	4270/6	4270/8	4270/9	4270/12	OV-36/622	75/2	76/2a	76/1
SiO2	52.76	52.99	53.02	51.84	52.60	46.31	46.75	46.23	48.08
TiO2	1.64	1.78	1.85	1.68	1.95	1.14	1.66	1.02	0.85
Al2O3	15.48	14.72	14.44	15.04	14.46	8.41	11.61	15.58	13.51
Fe2O3	8.83	9.37	9.48	9.20	9.82	13.19	12.70	8.73	9.08
MnO	0.13	0.15	0.15	0.14	0.15	0.18	0.16	0.17	0.14
MgO	6.11	5.07	5.10	5.87	5.98	19.21	10.40	7.18	9.34
CaO	7.97	8.89	8.95	8.92	7.80	9.50	9.73	8.24	10.00
Na2O	2.10	2.57	2.54	2.46	2.43	1.00	1.91	0.76	2.56
K2O	0.47	0.88	1.17	0.97	0.65	0.14	0.45	1.48	0.45
P2O5	0.22	0.25	0.26	0.23	0.28	0.14	0.13	0.12	0.09
LOI	3.91	2.88	2.98	3.15	3.42	n/a	4.11	10.28	4.90
Li	25.35	7.36	6.94	9.14	20.57	n/a	n/a	n/a	n/a
Be	1.72	1.63	1.74	1.61	1.31	n/a	n/a	n/a	n/a
Rb	19	41	41	41	24	6.94	7.01	43	9
Sr	510	374	367	407	548	179.34	147	275	210
Y	30.2	32.3	32.2	31.6	30.4	15.44	14.4	20.7	20.3
Cs	0.20	1.82	1.92	2.41	0.27	n/a	n/a	n/a	n/a
Ba	331	369	377	343	370	52.45	37.4	291	166
La	24.7	24.9	25.4	24.4	23.8	7.55	6.41	11.6	14.2
Ce	52.4	56.1	55.9	53.1	50.5	17.7	15.6	24.6	29.0
Pr	6.47	6.99	7.01	6.56	6.32	2.46	2.19	3.25	3.54
Nd	26.2	28.8	28.6	27.2	26.8	11.6	10.7	15.0	15.0
Sm	5.62	6.18	6.24	5.96	6.02	3.05	2.78	3.60	3.41
Eu	1.64	1.85	1.82	1.84	1.94	1.01	0.94	1.24	0.94
Gd	5.48	5.99	6.08	5.88	5.96	3.52	3.15	3.84	3.60
Tb	0.87	0.99	0.97	0.92	0.91	0.51	0.48	0.60	0.58
Dy	5.15	5.72	5.68	5.45	5.37	3.16	3.05	3.97	3.87
Ho	1.04	1.09	1.14	1.10	1.08	0.61	0.57	0.80	0.78
Er	2.75	3.02	3.02	2.95	2.80	1.62	1.46	2.25	2.24
Tm	0.40	0.50	0.44	0.43	0.40	0.21	0.21	0.33	0.33
Yb	2.43	2.77	2.72	2.58	2.41	1.38	1.31	2.18	2.17
Lu	0.35	0.38	0.38	0.37	0.35	0.19	0.19	0.32	0.32
Pb	7.36	7.32	7.30	6.34	6.30	2.90	2.31	4.62	5.34
Th	4.30	4.45	4.48	4.37	2.63	1.24	0.94	2.16	3.12
U	1.27	1.14	1.16	1.12	0.67	0.37	0.31	0.61	0.79
Sc	22.7	25.0	25.7	24.6	27.6	226	n/a	36.5	33.3
Ti	9427	10512	10509	10210	11635	6936	9762	7700	4892
V	174	179	189	186	217	n/a	n/a	n/a	n/a
Cr	322	325	322	395	208	91	n/a	n/a	n/a
Co	37.4	35.6	35.8	39.4	37.8	112	72	41.4	51.0
Ni	113	80.5	70.5	135	61.0	133	1324	117.5	346.4
Cu	65.1	39.8	38.5	32.7	34.3	132	118	98.8	70.1
Zn	92.5	97.0	97.7	96.1	103	79.9	n/a	86.0	87.7
Ga	20.08	20.42	20.40	20.78	19.52	5.26	n/a	n/a	n/a
Zr	206	220	221	215	206	79.9	81	91.4	87.5
Nb	29.6	18.0	18.0	16.0	16.6	5.25	5.71	6.3	5.7
Hf	4.99	5.41	5.35	5.20	4.90	2.18	2.22	2.40	2.38
Ta	1.01	1.06	1.06	1.02	0.85	0.35	0.38	0.42	0.39

Note: Oxides are given in wt.%, elements—in ppm. Samples, No: 1–10, 14, 15—Khalil site; 11–13—Kaya site; 16–26—Norilsk area (Section 2); Samples, No, Formations: 1–8, 10–14, 17–22—Syverminsky; 16, 17—Ivakinsky; 10, 23, 24—Gudchikhinsky; 15, 25, 26—Khakanchansky; bdl—below detection limit, n/a—element was not analyzed.

. Figure 9 shows diagram (SiO₂–Na₂O+K₂O) of the analyzed rocks.

Yellow, light brown and brown circles are rocks of the Syverminsky formation from different areas (Kylyumber–Khalil and Kaya sites, Norilsk–Lake Lama, respectively). They show a wide range of compositions belonging to basalt, basaltic andesite, trachybasalt, basaltic trachyandesite and trachyandesite (Figure 9). Most of the samples are concentrated in the basaltic andesite and basaltic trachyandesite fields: these rocks have similar SiO₂ content (Figure 9 and Figure 10a) but differ in alkalis concentrations. Rocks compositions of the Syverminsky formation of the Khalil area plot separately due to their enrichment in alkalis as compared with the rocks from the Kaya site and the Norilsk area (Section 2) and even with the Ivakinsky formation from Section 2. Figure 10 demonstrates the difference in alkalis between the Syverminsky rocks of the Khalil, Kaya and Norilsk area (Figure 10g,h) and the Khalil area rocks being higher in Na₂O whereas K₂O and P₂O₅ contents are similar for all three areas (Figure 10f–h). Concentrations of other oxides in the Syverminsky rocks from different areas are very similar (Figure 10b–e).

We have studied only one sample from the Gudchikhinsky formation in the Khalil site (Section 1), which was compared with two samples from the same formation in the Norilsk area (green triangles in Figure 9). This sample of the Gudchikhinsky formation correlates with the rocks of the lower part of this formation in the Norilsk area (lower subformation, T₁gd₁) represented by basalts. The basalts of the Khalil area show MgO = 7.96 wt.%) and Na₂O and K₂O (2.80 wt.% and 1.33 wt.%, respectively) (Figure 10g,h). These alkaline contents are not typical of the Gudchikhinsky formation in the Norilsk area (Table 2, Nos 23 and 24) where the total alkali content do not exceed 1.5 wt.%.

Tuffs compositions fall in the field of andesite and basaltic andesite (Figure 9, red symbols). They are characterized by low TiO₂ and high Al₂O₃. We attributed pyroclastic rocks to different formations based on trace element distribution (see later).

Trace elements. The patterns of trace elements for the Syverminsky rocks of both sections and of rocks outcropping in the Kaya river valley (Figure 11a; Table 2) are characterized by enrichment in LILE, negative Ta-Nb and positive Pb anomalies and elevated (Gd/Yb)n ratio close to 1.8–1.9. The compositions of trachybasalts of the Kaya site (samples 3.20–3.23) are quite homogenous and are absolutely similar to the Syverminsky rocks of Lake Lama area (samples 4270). A wide range of compositions characterizes the trachybasalts of the Khalil site. Despite the similar topology of patterns, they have large Pb and Sr anomalies in comparison with the samples of other areas.

There is a difference between the rocks of the Gudchikhinsky formation of the Khalil and Norilsk areas in trace elements. The Khalil rocks contain less Th and U in comparison with the similar rocks of the Norilsk area where there is essential variations in the content of many elements [27], but the Th and U content do not almost change. Thus, the low Th and U concentrations are a specific feature of the Gudchikhinsky basalts of the Khalil area (Figure 11b).

We studied two tuff samples, one is located in the tuff horizon (X-0) and the second one was taken from the volcanic structure outcropping in the Khalil site (X-37). They have similar compositions in term of major components (high SiO₂ content) but different rare elements distributions that allowed us to attribute them to different formations (Figure 11c). Sample X-37 is characterized by a deep slope of the right part of the pattern with (Gd/Yb)n = 1.9 and was attributed to the Syverminsky formation. Sample X-0 has a different pattern (with low (Gd/Yb)n = 1.5) and belongs to the Khakanchansky formation.

5.1.3. Isotope Composition of Volcanic Rocks

We have analyzed eight samples from the Khalil and Norilsk areas, mostly from the Syverminsky formation. The Gudchikhinsky picrites and Khakanchansky tuffs and Tuklonsky basalts have also been analyzed analyzed (

Table 3. Isotope composition of the the volcanic rocks.

№	1	2	3	4	5	6	7	8
Sample, No	X-3-3	X-3-2	X-15-2	X-28	76/2a	76/б	76/1	75/2
Rock	basalt	basalt	basalt	basalt	tuff	basalt	tuff	picrite
Weight, g	0.10672	0.11290	0.13360	0.10987	0.11450	0.18842	0.23990	0.13344
Rb, ppm	2.54	2.59	15.6	88.6	39.8	94.7	7.84	9.57
Sr, ppm	329	711	666	399	242	395	195	245
87Rb/86Sr	0.02227	0.01053	0.06796	0.64244	0.47512	0.69330	0.11636	0.11312
87Sr/86Sr	0.707445	0.707949	0.708479	0.709811	0.709010	0.708855	0.707744	0.705839
±2σ	0.000005	0.000006	0.000006	0.000004	0.000004	0.000006	0.000005	0.000004
Sri	0.707366	0.707912	0.708237	0.707526	0.707313	0.706380	0.707329	0.705435
ε Sr	44.82	52.57	57.19	47.10	44.09	30.83	44.31	17.42
Sm, ppm	7, 40	5, 65	6, 48	5, 60	3, 138	3, 90	3, 13	3, 938
Nd, ppm	35, 3	26, 0	30, 3	23, 5	13, 07	19, 31	13, 39	14, 34
147Sm/144Nd	0.12677	0.13129	0.12915	0.14379	0.14511	0.12203	0.14132	0.16597
143Nd/144Nd	0.512362	0.512373	0.512388	0.512397	0.512426	0.512356	0.512318	0.512785
±2σ	0.000003	0.000003	0.000006	0.000002	0.000004	0.000002	0.000002	0.000005
Ndi	0.512154	0.512157	0.512176	0.512161	0.512188	0.512156	0.512086	0512512
εNd	−3.14	−3.07	−2.70	−3.01	−2.47	−3.10	−4.47	3.85
206Pb/204Pb	19.0326	19.4625	23.5360	27.3000	18.4879	18.5422	18.2293	18.4164
±2σ	0.0005	0.0008	0.0009	0.0029	0.0016	0.0007	0.0004	0.0006
207Pb/204Pb	15.6165	15.6501	15.8283	15.7062	15.5697	15.5916	15.5421	15.5794
±2σ	0.0005	0.0007	0.0007	0.0017	0.0013	0.0008	0.0004	0.0007
208Pb/204Pb	38.7409	39.3205	40.7615	48.4215	38.4723	38.5210	38.2509	38.6319
±2σ	0.0016	0.0022	0.0018	0.0052	0.0032	0.0029	0.0012	0.0025
206Pb/204Pb *	18.7713	18.4227	18.8326	19.2021	18.1548	18.2085	17.7263	18.0827
207Pb/204Pb *	15.6031	15.5969	15.5873	15.2914	15.5526	15.5745	15.5163	15.5623
208Pb/204Pb *	38.5034	38.1128	37.9942	37.7191	38.0887	38.1367	37.7150	38.2471

Note. Numbers, formations: 1–4—Syverminsky, 5, 7—Khakanchansky, 6—Tuklonsky, 8—Gudchikhinsky. *—calculated at 250 Ma.

, Figure 12).

Data for flood basalts demonstrate a wide range of Nd-, Sr-isotopic compositions, these variations are typical of the Siberian trap province [30,31,61].

5.2. Intrusive Rocks

5.2.1. General Characteristic of Intrusive Rocks

Intrusions represent almost the 10% of the studied area (Figure 3). They are represented by sills or sill-like bodies located in sedimentary rocks (Devonian and Tunguska Group, C₂-P₂), i.e., they extend in submeridional (N–S) direction at 15–20 km and fall to the east at 10°–12° of the Nirungdinsky trough’s center. Several intrusive bodies form dikes, which cut volcanic rocks. The thickness of intrusions varies from 5–10 m to 150 m. The attribution of the intrusive rocks of the studied area to the intrusive plutonic complexes of the literature is a problem that is not easy to solve. The location of the territory on the border of the two tectonic structures (Figure 1) has led to emplacement of many intrusive bodies that are typical of both environments. According to the Legend to the Geological Map [62] this area comprises 3 complexes: Ergalakhsky (typical of the Norilsk area), Katangsky (typical of the Tunguska syneclise) and Kureysky (located between Kulyumber and Kureyka rivers). The intrusive bodies of these complexes have similar morphology, texture and composition. It is very difficult to distinguish between them without a detailed geochemical study. Traditionally coarse–grained and olivine gabbro-dolerites (with elevated MgO = 8–9 wt.%) were combined into the Kureysky complex while middle-grained olivine-bearing and olivine-free gabbro-dolerites were attributed to the Katangsky complex.

These three types of intrusive rocks, Ergalakhsky, Kureysky and Katangsky, were found at the Khalil site during the geological mapping (Figure 4). They are roughly equal in percentage. Bodies of the Ergalakhsky complex are localized along the valley of the stream Khalil (Intrusion 1 in Figure 4). A dike-like body of submeridional (N–S) direction located in volcanic rocks was named as the Khalil intrusion and attributed to the Kureysky complex (Intrusion 2 in Figure 4). It is 100–500-m thick, dips to the east (angles 45°–75°) and consists of gabbro-dolerites and leucogabbro-dolerites in the hanging side. One intrusive body, earlier attributed to the Katangsky complex, was attributed by us to the Norilsk complex based on its geochemical composition, which is close to the Norilsk complex (intrusion 3 in Figure 4). Several small subconcordant and nonconcordant intrusive bodies of the Katangsky complex were recognized in the Khalil and Kaya sites (Intrusion 4 in Figure 4; in Section 1, sample X-21, Figure 6).

5.2.2. Petrography of Intrusive Rocks

Ergalakhsky complex is represented by sills and sill-like bodies mostly concordant with sedimentary rocks of the Tunguska Group (Figure 3, Figure 4 and Figure 5). The bodies have thickness 10–20 m and length 3–5 km. They consist of trachydolerites (Figure 13; samples X-40, X-43, X-48, intrusion number 1 in Figure 4). The main rock-forming minerals are plagioclase (40–60 vol.%), clinopyroxene (35%–40%. titan-augite) orthopyroxene (0–3%), olivine (1% Magnetite, zircon, apatite are accessory minerals. Small bodies and contact zones of large sills are composed of fine-grained rocks with dolerite structure formed by differently oriented radial laths of plagioclase (0.2–0.3 mm) (60%–70%) and isometric grains of pyroxene (20%–35%) and rare olivine (0.05–0.1 mm, 5%–10%) (Figure 13a). The central part of large bodies consists of medium-coarse-grained rocks with poikilophytic structure (Figure 13b). The composition of minerals varies within the following ranges: plagioclase An_39–53, clinopyroxene Wo_41–43 En_35–39 Fs_18–22; Ol = Fo_42–52 (

Table 4. Composition of rock-forming minerals from intrusive rocks of the Khalil site, wt.%.

No	Sample, No	SiO2	TiO2	Al2O3	FeO	MnO	MgO	CaO	Na2O	K2O	Cr2O3	Total	Mineral
1	X-48	36.57	0.02	0.02	37.08	0.57	27.14	0.33	0.05	bdl	bdl	101.80	Ol
2	X-48	36.30	0.04	0.01	38.19	0.68	26.22	0.34	0.00	bdl	0.01	101.82	Ol
3	X-48	35.65	0.07	0.01	36.04	0.54	28.47	0.30	0.01	bdl	0.01	101.12	Ol
4	X-48	35.67	bdl	0.02	36.05	0.53	28.48	0.32	0.02	bdl	0.03	101.15	Ol
5	X-48	36.75	0.02	0.03	34.51	0.52	29.26	0.28	0.01	bdl	0.01	101.45	Ol
6	X-48	36.61	0.03	0.03	36.60	0.57	27.48	0.32	0.03	bdl	bdl	101.67	Ol
7	X-48	52.59	0.87	1.55	11.79	0.29	14.47	18.75	0.26	bdl	0.14	100.71	Cpx
8	X-48	51.96	0.95	1.65	12.61	0.33	13.99	18.05	0.22	0.03	0.07	99.87	Cpx
9	X-48	50.94	1.34	2.35	12.84	0.31	13.63	18.53	0.31	0.00	0.13	100.39	Cpx
10	X-48	56.37	0.12	27.06	0.74	0.02	0.10	9.91	5.01	0.70	bdl	100.03	Pl
11	X-48	57.78	0.14	26.06	0.71	bdl	0.07	8.79	5.40	1.00	bdl	99.94	Pl
12	X-48	56.11	0.12	27.07	0.52	bdl	0.12	10.21	5.03	0.66	bdl	99.84	Pl
13	X-48	55.49	0.11	27.56	0.66	0.01	0.11	10.48	4.85	0.60	bdl	99.87	Pl
14	X-48	52.32	0.91	1.48	12.07	0.26	14.45	18.98	0.25	bdl	0.08	100.84	Cpx
15	X-48	51.56	1.35	2.32	12.47	0.32	13.82	18.86	0.27	0.01	0.13	101.10	Cpx
16	X-32	52.16	1.00	1.71	14.32	0.31	15.56	15.56	0.23	0.00	0.02	100.87	Cpx
17	X-32	49.25	bdl	0.15	25.03	0.21	12.13	1.51	0.01	0.12	0.07	88.50	Cpx
18	X-32	46.97	bdl	0.78	27.18	0.35	10.89	1.34	0.03	0.13	0.04	87.77	Sp
19	X-32	44.09	bdl	0.30	31.56	0.47	8.39	1.80	0.02	0.09	0.07	86.82	Sp
20	X-32	49.27	bdl	0.13	26.02	0.30	11.82	1.81	0.02	0.13	0.09	89.66	Sp
21	X-32	44.43	bdl	0.43	32.60	0.54	8.46	1.76	0.02	0.07	0.07	88.40	Sp
22	X-32	44.51	bdl	2.35	29.87	0.45	9.52	1.81	0.00	0.09	0.07	88.69	Sp
23	X-32	52.02	0.72	3.42	8.25	0.17	15.53	19.65	0.23	bdl	0.31	100.31	Cpx
24	X-32	48.75	0.05	27.66	3.97	0.09	1.26	13.17	2.35	0.11	bdl	97.41	Pl
25	X-32	50.61	0.03	30.80	0.97	0.01	0.10	14.60	3.00	0.15	0.02	100.28	Pl
26	X-32	52.02	0.05	29.85	0.83	0.04	0.12	13.68	3.32	0.16	0.06	100.12	Pl
27	X-32	50.81	0.01	30.48	0.80	0.03	0.12	14.28	2.71	0.15	0.03	99.41	Pl
28	X-32	49.28	0.01	32.29	0.82	0.03	0.08	15.93	2.23	0.09	bdl	100.75	Pl
29	X-32	55.81	0.11	27.27	0.88	0.00	0.07	10.52	4.96	0.31	0.02	99.96	Pl
30	X-35	0.26	41.90	0.13	51.61	3.86	0.09	0.01	0.06	bdl	0.04	97.95	Ilm
31	X-35	0.38	9.07	4.04	77.60	1.53	2.55	0.02	0.00	bdl	0.02	95.26	Mag
32	X-35	53.19	0.09	29.22	1.17	0.02	0.08	12.37	4.07	0.26	0.01	100.50	Pl
33	X-35	50.94	0.68	3.69	8.07	0.18	14.79	21.28	0.31	bdl	0.09	100.04	Cpx
34	X-35	51.71	0.57	3.05	7.44	0.20	15.47	21.26	0.28	bdl	0.10	100.12	Cpx
35	X-35	53.72	0.55	1.61	7.83	0.50	15.45	20.08	0.55	0.04	bdl	100.33	Cpx
36	X-35	51.18	0.88	3.77	9.61	0.21	14.38	21.02	0.38	bdl	0.01	101.46	Cpx
37	X-35	51.57	0.03	30.35	1.03	0.02	0.08	13.93	3.32	0.17	0.01	100.50	Pl
38	X-35	54.89	0.05	27.95	0.88	bdl	0.09	11.09	4.78	0.32	bdl	100.05	Pl
39	X-35	59.18	0.04	23.67	1.90	0.03	1.07	5.75	6.62	0.31	bdl	98.57	Pl
40	X-35	53.19	0.11	29.35	1.57	0.04	0.04	12.75	3.96	0.20	bdl	101.22	Pl
41	X-7	51.42	0.61	2.97	7.50	0.18	15.01	21.35	0.30	bdl	0.15	99.47	Cpx
42	X-7	53.06	0.03	0.31	6.36	0.32	15.56	23.55	0.15	bdl	0.03	99.37	Cpx
43	X-7	49.22	1.13	3.66	10.16	0.28	14.27	20.01	0.40	bdl	bdl	99.12	Cpx
44	X-7	50.09	0.85	2.77	9.85	0.29	14.79	19.97	0.39	0.01	0.01	98.99	Cpx
45	X-7	50.77	0.50	3.11	7.09	0.18	15.79	21.45	0.28	bdl	0.35	99.53	Cpx
46	X-7	54.94	0.09	28.01	0.86	0.01	0.08	10.52	4.88	0.35	bdl	99.74	Pl
47	X-10	54.77	0.08	27.73	0.92	bdl	0.12	10.76	4.63	0.33	bdl	99.33	Pl
48	X-10	54.41	0.10	27.38	0.92	bdl	0.12	11.67	4.30	0.26	0.02	99.19	Pl
49	X-10	42.59	0.20	12.71	11.38	0.13	14.29	11.20	3.28	0.50	0.02	96.29	Am
50	X-19	67.91	bdl	20.54	0.26	bdl	0.01	1.08	9.98	0.03	bdl	99.82	Pl
51	X-19	52.50	0.48	2.63	9.07	0.36	18.18	11.89	1.05	0.28	bdl	96.44	Am
52	X-19	29.41	34.51	0.77	2.08	0.07	0.02	27.02	0.00	bdl	0.01	93.90	Titanite
53	X-19	49.02	1.16	4.4	10.01	0.22	13.98	20.33	0.41	bdl	bdl	99.53	Cpx
54	X-19	51.05	0.66	2.76	9.86	0.25	15.05	19.77	0.33	bdl	bdl	99.73	Cpx
55	X-19	48.9	1.13	4.44	10.31	0.26	13.85	20.14	0.41	bdl	bdl	99.44	Cpx
56	X-19	50.9	0.71	2.73	9.87	0.29	15.05	19.42	0.38	bdl	bdl	99.35	Cpx
57	X-39	50.27	0.88	3.52	8.62	0.18	14.72	20.81	0.20	bdl	0.15	99.36	Cpx
58	X-39	50.93	0.83	3.69	8.28	0.16	15.35	19.56	0.22	bdl	0.35	99.36	Cpx
59	X-39	50.84	0.56	3.29	8.94	0.20	16.04	19.07	0.21	bdl	0.23	99.39	Cpx
60	X-39	50.70	0.84	3.17	11.56	0.25	14.09	18.84	0.24	bdl	0.06	99.75	Cpx
61	X-39	50.06	0.94	3.43	11.83	0.25	14.98	17.57	0.25	0.01	0.09	99.40	Cpx
62	X-39	49.51	0.04	31.36	0.54	bdl	0.26	15.33	2.61	0.09	bdl	99.75	Pl
63	X-39	52.27	0.03	29.66	0.99	bdl	0.41	12.24	3.84	0.17	bdl	99.61	Pl
64	X-39	49.48	bdl	30.17	1.26	0.02	0.85	14.57	2.55	0.11	bdl	99.00	Pl
65	X-39	50.71	0.04	30.34	0.70	bdl	0.29	14.89	2.79	0.10	0.01	99.86	Pl
66	X-39	50.61	0.03	31.34	0.67	0.01	0.24	14.00	2.98	0.12	bdl	99.99	Pl
67	X-39	49.34	0.09	4.97	17.84	0.47	12.26	10.85	0.96	0.05	0.01	96.84	Am

Note: Minerals names are in Table 1. bdl—below detection limit.

).

Kureysky complex. Here we consider a large dike-like massif in the Khalil site which was previously attributed to the Kureysky complex. It was named the Khalil intrusion during geological mapping of this area [62] (Figure 4, intrusion 2). It consists of middle-, large-grained olivine gabbro-dolerites and gabbro-dolerites. The main minerals are olivine, clinopyroxene, plagioclase; rare minerals include biotite, magnetite and apatite. The composition of olivine (Figure 9, Table 3) changes from Fo₄₉ to Fo₅₆. The CaO (up to 0.32 wt.%) and Ni (0.05–0.17 wt.%) contents are low. This composition is strongly different from olivine of the ore-bearing intrusions of the Norilsk area, in particular the Norilsk 1 intrusion studied by us in the core of borehole DM-27 (the second part of this article) as well as from available data in the literature [63,64,65]. Clinopyroxene is more stable in composition: the Mg# ranges in interval 64–74. The admixture of chromium in it is practically absent (at the level of sensitivity of the EPMA method) and TiO₂ content does not exceed 1 wt.%. Maximum concentrations (wt.%): Al₂O₃—2.25, Na₂O—0.40. The composition of plagioclase varies from An₅₆ to An₇₀. Magnetite contains 12–14 wt.% TiO₂. The mineral composition of the Khalil intrusion was studied in the samples X-35 and X-19 (Table 4).

The reference object of the Kureysky complex is the Dzhaltulsky massif located several kilometers south of the Kulyumber area. We have analyzed samples from the borehole OKG-13. Olivine from one sample corresponds to the average value of the olivine compositions in the Kylyumber massif: it is characterized by very low concentrations of calcium and nickel (0.07–0.17 wt.% CaO and 0.03–0.06 wt.% NiO) at the same Fo_72–73 of the mineral. Pyroxene is more magnesian-rich (Mg# = 77–78).

Intrusions of the Katangsky complex are usually composed of fine-medium-grained homogeneous gabbro-dolerites and olivine-bearing gabbro-dolerites. They have usually a dolerite, poikilophytic structure where plagioclase laths (0.1–0.3 microns) are enclosed in large grains of pyroxene (1–1. 5 mm). The composition of olivine in olivine gabbro-dolerites (sample X-15) is close to the olivine composition from the Kureysky complex but differs in higher nickel contents (up to 0.19 for Fo₇₃; it is close in composition to olivine from the Norilsk 1 intrusion. Plagioclase changes from An₅₆ to An₇₀. The Mg# number of clinopyroxene varies from 53 to 73 and orthopyroxene from 58 to 69. Magnetite contains 12–14 wt.% TiO₂. The mineral composition of the Khalil intrusion was studied in the sample X-19 and X-35 (Table 4). The compositions of rock-forming minerals from the Katangsky complex will be described in the second part of the article.

5.2.3. Chemical Composition of Intrusive Rocks

The compositions of the different intrusive complexes are given in

Table 5. Composition of intrusive rocks.

No	1	2	3	4	5	6	7	8	9	10
Sample, No	X-6	X-6/1	X-6-5	X-7	X-8	X-8-3	Х-18-1	X-19	X-25	Х-35
SiO2	46.96	46.81	48.76	46.93	47.75	47.93	47.76	47.46	46.33	47.27
TiO2	1.31	1.32	1.51	1.56	1.35	1.38	1.66	1.79	1.58	1.6
Al2O3	14.65	14.44	14.68	12.83	14.69	14.72	14.3	14.09	13.39	13.83
Fe2O3	12.17	12.36	13.15	14.07	11.99	12.87	13.64	14.44	14.43	14.4
MnO	0.157	0.168	0.196	0.215	0.199	0.174	0.21	0.165	0.224	0.208
MgO	6.99	7.06	6.99	7.25	7.16	7.37	6.94	4.94	6.81	6.48
CaO	10.52	10.62	10.44	10.93	8.75	10.58	10.03	9.46	10.71	10.79
Na2O	4.13	3.7	2.59	3.15	4.43	3.09	2.84	3.94	2.87	2.78
K2O	0.08	0.06	0.52	0.89	0.51	0.25	0.41	1.17	0.93	0.87
P2O5	0.14	0.13	0.17	0.22	0.14	0.14	0.22	0.29	0.21	0.2
LOI	2.77	3.07	0.78	1.86	2.9	1.38	1.86	2.11	2.24	1.35
Rb	1.44	0.76	13.5	19.5	15.9	6.7	9.4	22.1	25.5	21.2
Sr	197	193	192	548	867	203	255	591	687	412
Y	25.1	25.2	30.1	30.6	25.1	26.4	32.3	39.2	29.6	32.9
Ba	67	62	162	199	96	85	157	227	219	211
La	6.48	6.91	8.97	11.48	6.73	6.34	11.13	14.08	9.19	11.67
Ce	15.7	16.4	21.9	25.2	16.2	15.7	26.4	31.9	23.5	27.2
Pr	2.18	2.31	2.92	3.36	2.34	2.30	3.47	4.28	3.01	3.43
Nd	10.1	10.8	14.0	14.2	10.5	9.69	16.6	19.2	14.3	16.2
Sm	3.10	3.24	3.89	3.88	2.99	2.98	4.38	5.41	4.02	4.35
Eu	1.05	1.13	1.30	1.38	1.00	1.06	1.39	1.70	1.25	1.38
Gd	3.71	3.97	4.59	4.77	3.83	3.85	5.47	5.83	4.87	4.88
Tb	0.68	0.71	0.76	0.76	0.65	0.66	0.88	0.99	0.82	0.83
Dy	4.19	4.60	5.02	5.08	3.98	4.55	5.93	6.56	5.30	5.30
Ho	0.93	0.96	1.03	1.15	1.01	0.93	1.20	1.37	1.10	1.07
Er	2.62	2.75	2.98	2.83	2.52	2.63	3.67	4.02	3.34	3.31
Tm	0.37	0.38	0.41	0.46	0.36	0.40	0.50	0.60	0.45	0.47
Yb	2.46	2.70	2.91	3.08	2.63	2.56	3.34	3.87	3.01	3.14
Lu	0.37	0.39	0.42	0.46	0.39	0.36	0.51	0.59	0.45	0.46
Pb	0.99	0.71	3.04	1.05	1.03	1.51	2.22	1.58	0.99	1.54
Th	0.97	0.89	1.22	1.69	0.97	1.07	1.84	2.36	1.43	1.68
U	0.29	0.33	0.40	0.85	0.38	0.34	0.85	1.19	0.78	0.87
Sc	31.1	38.9	39.5	32.6	29.8	32.3	37.8	28.3	39.3	35.6
V	281	266	299	304	294	299	322	325	340	336
Cr	257	233	197	210	245	260	165	29	197	163
Co	42.8	51.9	47.5	48.8	36.8	44.1	45.7	48.8	50.1	46.3
Ni	110	119	108	103	106	112	101	50	112	93.4
Cu	42.9	20.8	157	123	43.3	92.8	146	133	82.1	132
Zn	63.6	74.1	116.3	71.7	63.0	71.4	115.0	54.0	87.1	94.6
Zr	78.8	87.5	106	108	95.7	85.5	131	181	108	130
Nb	3.76	3.96	5.92	6.67	4.30	4.33	6.88	8.83	6.35	6.61
Hf	2.56	2.40	2.60	2.92	2.74	2.32	3.45	4.64	2.83	3.05
Ta	0.24	0.26	0.34	0.42	0.27	0.27	0.42	0.61	0.38	0.42
No	11	12	13	14	15	16	17	18	19	20	21
Sample, No	Х-29	Х-31	Х-32	Х-33	Х-34	Х-43	X-44	X-46	X-48	X-40	DM-27/20
SiO2	48.17	48.06	48.14	47.94	47.89	47.65	47.12	50.68	51.06	51.46	47.20
TiO2	0.96	0.96	1	1.03	0.99	0.92	0.95	2.46	2.42	2.41	0.94
Al2O3	15.19	15.07	14.71	14.8	14.87	15.02	14.58	13.51	13.88	13.55	16.46
Fe2O3	10.64	10.95	11.25	11.5	11.14	10.89	11.17	12.38	13.68	13.62	11.02
MnO	0.157	0.166	0.172	0.16	0.168	0.147	0.178	0.161	0.135	0.186	0.15
MgO	7.97	8.4	8.55	7.92	8.35	8.9	8.3	3.24	3.1	3.12	6.11
CaO	11.72	11.73	11.78	11.35	11.66	10.54	11.86	7.92	6.73	6.94	11.21
Na2O	2.06	2.07	2.05	2.17	1.96	2.07	1.76	3.22	3.2	3.06	3.41
K2O	0.37	0.23	0.21	0.22	0.15	0.33	0.22	2.15	2.05	2.37	0.62
P2O5	0.08	0.09	0.08	0.09	0.08	0.08	0.08	0.77	0.78	0.76	0.15
LOI	2.55	2.13	1.86	2.66	2.59	3.25	3.57	3.16	2.82	2.12	2.29
Rb	13.7	6.1	9.0	8.0	5.1	8.7	6.6	49.7	49.0	56.6	19.8
Sr	261	226	233	236	235	205	212	383	404	437	369
Y	17.3	17.5	18.9	20.9	18.3	18.2	19.2	50.5	50.7	49.7	20.8
Ba	131	90	82	105	73	109	90	869	756	833	143
La	4.61	4.86	5.98	6.12	5.30	5.03	6.28	51.69	45.42	44.66	6.32
Ce	11.0	11.3	12.6	14.2	12.5	12.1	14.7	111.8	98.3	96.1	15.1
Pr	1.43	1.56	1.65	1.87	1.67	1.60	1.92	13.57	12.24	11.98	2.00
Nd	6.73	7.02	8.09	8.99	8.34	7.88	8.72	55.0	47.2	46.4	9.8
Sm	2.09	2.31	2.38	2.55	2.37	2.29	2.57	12.00	11.16	11.47	2.68
Eu	0.76	0.85	0.87	0.96	0.91	0.84	0.98	3.51	3.12	3.10	0.99
Gd	2.48	2.70	2.73	3.03	2.86	2.79	3.03	11.10	9.31	9.09	3.43
Tb	0.45	0.40	0.48	0.50	0.47	0.45	0.53	1.73	1.54	1.49	0.58
Dy	2.98	3.03	3.03	3.41	3.01	2.91	3.36	9.56	8.84	8.74	3.82
Ho	0.63	0.60	0.61	0.67	0.60	0.58	0.69	1.87	1.77	1.73	0.80
Er	1.83	1.93	1.82	2.00	1.80	1.75	2.09	5.30	4.67	4.70	2.15
Tm	0.26	0.28	0.26	0.28	0.25	0.25	0.27	0.70	0.64	0.67	0.32
Yb	1.54	1.56	1.74	1.84	1.64	1.70	1.90	4.50	4.11	4.07	2.18
Lu	0.26	0.26	0.24	0.28	0.24	0.25	0.27	0.67	0.58	0.64	0.33
Pb	1.42	2.81	3.02	2.16	0.97	3.26	1.16	10.55	9.07	10.67	1.10
Th	0.74	0.76	0.65	0.79	0.61	0.80	0.85	4.85	5.43	5.10	1.06
U	0.17	0.17	0.15	0.19	0.14	0.20	0.23	1.39	1.38	1.30	0.42
Sc	30.8	29.1	38.7	37.5	38.9	36.5	39.7	23.8	27.1	27.4	40.7
V	270	271	270	295	291	267	263	142	141	138	261
Cr	397	418	406	329	336	398	367	35	37	32	282
Co	42.5	47.1	48.2	49.2	48.1	45.3	54.2	26.6	22.6	24.8	43.6
Ni	106	112	121	112	122	121	125	14.8	15.4	18.2	93.6
Cu	100	103	117	136	140	93	113	21.4	64.8	34.1	90.9
Zn	69.6	64.3	88.4	92.6	96.5	68.6	70.8	104.6	95.4	132.8	58.5
Zr	65.4	66.1	64.1	72.7	52.8	68.1	66.3	413	450	436	115
Nb	3.33	3.48	3.00	3.40	3.00	3.21	3.50	28.47	31.14	29.22	4.04
Hf	1.71	1.81	1.51	1.77	1.42	1.60	1.84	8.88	10.00	9.74	1.94
Ta	0.35	0.26	0.20	0.25	0.21	0.21	0.21	1.60	1.70	1.71	0.23
No	22	23	24	25	26	27	28	29	30	31
Sample,No	DM-27/46	DM-27/65	DM-27/86.1	DM-27/100	DM-27/127	DM-27/142.3	DM-27/175.3	TK-4	TK-3	OKG-13/43.7
SiO2	49.22	48.56	49.86	44.66	48.67	38.70	32.71	43.18	40.00	49.66
TiO2	1.11	0.94	0.81	0.88	0.63	0.57	1.17	0.56	0.41	0.37
Al2O3	15.66	15.29	15.94	15.66	18.71	9.80	13.62	8.35	5.96	17.34
Fe2O3	11.05	9.83	8.12	10.47	8.73	15.26	19.32	16.96	18.20	7.59
MnO	0.13	0.12	0.13	0.16	0.14	0.20	0.13	0.22	0.23	0.12
MgO	4.51	5.51	5.59	7.94	8.04	24.50	5.72	22.61	27.07	8.81
CaO	9.77	11.91	13.26	15.01	10.82	5.25	6.55	5.42	4.40	14.02
Na2O	5.15	4.44	3.52	2.31	2.25	1.01	2.52	0.91	0.46	1.94
K2O	0.37	0.39	0.25	0.47	0.26	0.36	0.89	0.25	0.17	0.20
P2O5	0.25	0.17	0.15	0.55	0.10	0.12	0.49	0.07	0.08	0.03
LOI	2.38	2.51	1.96	1.42	1.25	1.96	2.82
Rb	10.0	9.6	3.4	8.1	4.9	9.2	25.4	2.78	3.03	1.24
Sr	362	294	277	230	248	116	347	7.51	6.12	3.63
Y	24.5	22.7	19.9	15.8	15.5	10.1	17.4	121	117	262
Ba	56	95	78	77	113	85	340	12.6	8.5	9.5
La	9.20	6.63	5.28	4.72	4.94	3.21	16.87	75.5	45.7	90.0
Ce	21.17	16.37	13.04	11.30	11.41	7.54	38.80	4.10	2.36	2.80
Pr	2.72	2.20	1.82	1.52	1.51	1.01	4.42	9.48	5.33	6.32
Nd	12.7	10.8	8.95	7.40	7.29	4.98	18.7	1.30	0.75	0.87
Sm	3.30	2.96	2.52	2.05	2.00	1.32	3.74	6.13	3.60	4.26
Eu	1.05	0.99	0.87	0.76	0.80	0.45	1.15	1.70	1.03	1.23
Gd	4.10	3.77	3.29	2.67	2.54	1.69	3.69	0.57	0.35	0.59
Tb	0.66	0.62	0.55	0.43	0.42	0.28	0.55	2.03	1.31	1.49
Dy	4.41	4.16	3.63	2.95	2.90	1.88	3.37	0.34	0.22	0.26
Ho	0.92	0.85	0.73	0.60	0.60	0.39	0.65	2.26	1.49	1.73
Er	2.65	2.37	2.31	1.63	1.62	1.11	1.71	0.47	0.31	0.35
Tm	0.37	0.35	0.31	0.24	0.24	0.17	0.26	1.38	0.92	1.01
Yb	2.60	2.32	2.09	1.66	1.68	1.11	1.67	0.19	0.13	0.14
Lu	0.38	0.35	0.31	0.25	0.25	0.17	0.26	1.31	0.89	0.95
Pb	0.80	0.49	1.93	1.49	2.63	3.11	14.13	0.20	0.14	0.14
Th	1.47	1.21	1.02	0.76	0.96	0.52	1.87	4.10	3.81	3.71
U	0.57	0.41	0.36	0.30	0.35	0.24	0.89	0.49	0.35	0.32
Sc	33.3	45.6	49.3	48.7	25.5	21.7	21.2	0.18	0.07	0.09
V	336	266	222	205	192	106	203	150	107	224
Cr	28	42	151	521	384	4732	305
Co	43.8	39.8	34.1	42.0	48.0	132.4	365.9	205	231	53
Ni	86.0	68.3	74.6	129	214	1481	12638	4021	3974	304
Cu	141	66.6	61.7	95.4	99.0	944	10619	2428	4509	361
Zn	73.2	64.3	53.2	68.5	114.2	113.1	183.5	6.07	30.2	52.3
Zr	118	116	115	91.0	65.5	35.7	114	38.6	25.5	24.6
Nb	4.86	4.21	3.65	2.71	3.21	1.76	12.13	2.08	1.58	1.93
Hf	2.58	2.14	1.76	1.52	1.60	0.84	2.25	0.99	0.75	0.67
Ta	0.29	0.25	0.23	0.16	0.20	0.10	0.67	0.13	0.10	0.11

Note: Samples. N: 1–20—Khalil area, 21–28—Norilsk area (Norilsk 1 intrusion), 29–31—Dzhaltulsky massif.

and illustrated in Figure 14. Trachydolerites of the Ergalakhsky complex (Intrusion 1) differ from the other rocks in higher SiO₂, P₂O₅, Na₂O and especially in TiO₂ and K₂O contents (up to 2.5 wt.%. Figure 12e–g) whereas rocks from the other complexes contain less than 1 wt.% K₂O, and low SiO₂., MgO and CaO concentrations.

Low MgO contents (<10 wt.%) characterize all studied samples excluding one sample of picritic gabbro-dolerite from the Norilsk 1 intrusion (24.5 wt.% MgO). This sample contains sulfide mineralization and, due to high sulfide content, has high Fe and low CaO and alkalis’ concentrations. The Norilsk 1 intrusion is characterized by wide compositional range because it consists of different rocks that form separate layers within the intrusive body. These rocks are enriched in Al₂O₃ and depleted in MnO, TiO₂ and Fe₂O₃ in comparison with the other intrusions of the Khalil site excepting the intrusive body 3. There is a good correlation between rocks from the Norilsk 1 and Intrusion 3 (Figure 4) for all major elements—TiO_2, SiO₂, alkalis and P₂O₅. Only CaO content in gabbro-dolerites in the Intrusion 3 is slightly lower than that in the Norilsk 1 intrusion. We attributed this Intrusion 3 to the Norilsk intrusive complex (Norilsk-type). In both cases the lower contents of TiO₂ in the Norilsk 1 intrusion and Intrusion 3 are typical of the Norilsk complex. According to numerous data, the TiO₂ concentration from the Norilsk 1 intrusion is 0.87 wt.%, i.e., <1% [8,40,66].

Most interesting is the comparison of the compositions of the Kureysky and Katangsky complexes; these complexes are the most common in this area. They consist of gabbro-dolerites belonging to rocks of normal alkalinity (less than for the Ergalakhsky rocks). Figure 14 shows their identical composition in major components and their difference with the Ergalakhsky intrusion. Only Na₂O contents are higher in respect to the rocks of the Katangsky complex. Probably, due to alteration of the Katangsky rocks.

The large Dzhaltulsky massif is considered as a reference intrusion of the Kureysky complex. We used three samples from this massif to compare these rocks with other intrusions of the Kulyumber area. Our data show that the Dzhaltulsky massif differs from both the Kureysky and Katangsky intrusions by low TiO_2, alkalis, Fe₂O₃ and high MgO, Al₂O₃, CaO. Thus, we believe that intrusions attributed to the Kureysky complex in the Khalil site belong to the Katangsky complex because they differ of the Dzhaltulsky massif in all major elements.

The distribution of trace elements in rocks of different complexes is shown in a series of spider diagrams (Figure 15) and on binary diagrams (Figure 16).

In Figure 15 the intrusive rocks show two distinct compositional patterns: (1) enrichment in LILE with small Ta-Nb negative anomaly and depletion in other HFSE and REE elements (Ergalakhsky complex; Figure 15a); (2) strong negative Ta-Nb and Sr anomalies and minor depletion in other HFSE and REE elements (Figure 15b–f). The second pattern has some differences between intrusions. The greatest variation in the content of trace elements characterizes the Norilsk 1 massif (Figure 15b) due to different olivine content of the rock: the most depleted patterns are typical of the picritic gabbro-dolerites. The patterns of the Katangsky and Kureysky (Khalil intrusion) complexes are very close to each other (Figure 15c,d). Rocks of the Dzhaltulsky massif are the most depleted in all incompatible elements. Intrusive body of the Norilsk-type (intrusion 3 in Figure 4) approaches to the composition of the Dzhaltulsky massif (Figure 15e,f).

Ratios of indicator elements detect differences between intrusions of the second type. The (Gd/Yb)n and (La/Sm) n ratios reflect the slope steepness of the right and central parts of the patterns (Figure 16a), whereas the (La/Yb)n ratio characterizes the pattern inclination. To use these indicator element ratios see we did not consider samples of the Ergalakhsky complex in Figure 16a because much higher values of these ratios characterize them. This diagram shows that the (U/Nb)n ratio is only significant difference between them (Figure 16b). The highest values are typical of the Khalil intrusion presumably assigned to the Kureysky complex. However, the Dzhaltulsky massif, which is considered the rock-type of this complex, is characterized by the lowest values of the (U/Nb)n ratio. Intrusion 3 defined preliminarily as Norilsk-type intrusion is close to the Dzhaltulsky massif according to this parameter. Therefore, the (U/Nb)n ratio allows separating intrusions of the different complexes.

Comparison of rocks from different massifs in term of ore elements (excluding rocks with rich sulfide mineralization) indicates their same content of metals such as vanadium and chromium (Figure 17a), nickel and copper (Figure 17b), excepting the Ergalakhsky complex, which is depleted in these metals.

6. Discussion

6.1. Volcanic Rocks

For the first time we have studied in detail the igneous rocks outside the Norilsk district using the modern geochemical methods. The volcanic rocks of the Kulyumber river valley have been previously subdivided into several formations similar to the formations of the Norilsk region (Table 5, [55]). The Ivakinsky formation is absent in the Nirungdinsky trough. Its composition studied in the Lama Lake area (Section 2) corresponds to the composition of the Ivakinsky rocks in the Kharaelakh trough [29,32]. The Syverminsky formation has been studied also in two sites of the Kulyumber river valley, the Khail and Kaya. Our data allowed to conclude that this formation varies along its stretch. Although the textural and structural features of rocks vary slightly, their chemical composition change significantly. In the Norilsk region (Lama Lake, Section 2), the rocks show a constant homogeneous composition, with small variations in the concentrations of the major elements such as MgO-5–6 wt.%, TiO_2–1.6–2 wt.%, alkalis-2.6–3.7. Similar variations of these elements have been found in the Kharaelakh trough [29] and Sunduk mountain [32]. Within the Kulyumber river valley, the contents of major oxides in rocks change more significantly. Trachydolerites of Section 1 contain (wt.%): MgO = 3.4–6.9, TiO₂ = 1.2–1.8, alkalis = 5.2–6.3, whereas those (samples 3-2-2 and 3-3-3) at the Khalil significantly differ showing low magnesium (3.4 wt.% MgO) and high alkalis (up to 7.1 Na₂O + K₂O wt.%) content. Probably, these differences are due to secondary alterations of the rocks as suggested by the presence of many pyrite crystals. The homogenous compositions are typical of the Syverminsky rocks with respect to the La/Sm, Gd/Yb and U/Nb ratios, especially of the rocks at the Nirungdinsky trough.

The Gudchikhinsky formation in the Norilsk region is subdivided into three subformations [14,55] that differ in composition. They are represented by porphyry basalts, picrites and glomeroporphyritic basalts, respectively. Picrites of the middle subformation are the most stable along the stretch, while the basalts of the lower and upper subformations pinch out from the west to east. The studied sample from the Kulyumber river valley corresponds to the rocks of the lower subformation, although it differs from them in its aphyric texture. The Gudchikhinsky rocks (lower and middle subformations) were studied within the Kharaelakh [29] and Norilsk [67] troughs. The studied basalts of the Khalil site contain more MgO (8 wt.%) in comparison with similar basalts of the Norilsk region, where the Gudchikhinsky basalts contain 6.3 ± 0.5 wt.% in average (67 analyses, [68]). Similar data were obtained for basalts in the Kharaelakh trough, where MgO varies in narrow range of 6–7 wt.%, The basalts of the lower subformation of the Gudchikhinsky formation in the Norilsk trough (boreholes OM-6 and OM-25, [67]) show less magnesium content, with MgO ranges from 4.3 wt.% to 4.8 wt.%.

The trace element ratios show the differences between the rocks of the studied areas more clearly. The (Gd/Yb)n ratio reflecting the inclination of the right part of patterns changes from 2.0 to 2.3 in rocks of the Norilsk area and it is close to the ratio established for the Gudchikhinsky rocks in the Khalil site (2.0). The La/Sm ratio is more variable, and it demonstrates the differences between rocks of the Gudchikhinsky formation located in the different tectonic structures of the Norilsk area. The picrites of the Kharaelkh trough are characterized by values of 1.3–1.5, while basalts have 1.5–1.7. The highest difference between basalts of the lower subformation and picrites of the middle subformation occurs in the rocks of the Norilsk rough, where they are characterized by (La/Sm)n ratio of 2.2 and 1.3–1.7, respectively. The U/Nb ratio has a wide range in the Gudchikhinsky rocks. The basalts of the Norilsk trough have low ratio (1.4), while the picrites have (U/Nb)n = 2.0–4.0. The difference between basalts and picrites within the Kharaelakh trough is also significant, 0.9 for basalts and 1.7–2.2 for picrites. These values are very close to the values that we obtained for basalts of the Nirungdinsky trough (0.7) and for picrites of the eastern part of the Norilsk area (1.8 and 2.4).

The Khakanchansky formation consists of tuffs. The data on the Khakanchansky rocks in literature are restricted in comparison with the data on other formations. Previously we described these rocks from the upper part of Section 2 [58], Lama Lake area and in the Norilsk trough [67]. The contents of major elements in tuffs vary significantly but the distribution of trace elements and their ratios are quite homogenous (La/Sm)n = 2.3–3.3, (Gd/Yb)n = 1.5–1.6, (U/Nb)n = 4.7–6. The composition of tuff from the Khalil area is close to the compositions of tuffs in the Norilsk area (excepting U/Nb). Published data on the composition of the Khakanchansky rocks at the Khantayskoe Lake [69] significantly differ in the La/Sm ratio, which varies from 1.5 to 1.8. According to our data, similar values are typical of the Tuklonsky formation, so it is likely that these tuffs belong to this formation.

In summary, the obtained geochemical data on the volcanic rocks in the Kulyumber river valley allows us to attribute them to the known formations despite some variations in their compositions.

6.2. Intrusive Rocks

The diagnostic of intrusive rocks in the Kulyumber river valley is inconveniently due to their similar texture and structure and close chemical composition. Preliminary attribution to intrusive complexes is based on the morphology and inner structure of intrusive bodies. Geological map [53] indicates that three intrusive complexes occur in this area, i.e., Ergalakhsky, Katangsky and Kureysky. We have studied four main intrusions in the Khalil site (Figure 4) and two intrusions from the Norilsk area (the Norilsk 1) and Kureyka river valley (the Dzhaltulsky massif) representing the Norilsk and the Kureysky complexes. To compare these intrusions between them and with standard Norilsk and Kureysky complexes we used the same parameters as we used for the volcanic rocks (

Table 6. Comparison of the mineralogical and geochemical features of the volcanic rocks.

Formation	Area, Site	Sample No	Texture, Structure	Minerals		MgO, wt.%	TiO2, wt.%	Na2O+K2O, wt.%
Ivakinsky P3iv	Norilsk, Lama Lake	4270 4270/4	porphyric porphyric			3.6 3.4	3.9 2.4	4.3 5.0
Syverminsky T1sv	Kulyumber, Khalil	X-3-2 X-3-3 X-28 (X-20 X-20 X-21/3 X-22 X-24 X-26) X-37 tuff	tholeiitic      tholeiitic- poikilophytic	An40-55, Cpx Mg#		4.0 3.4 5.7 (3.4–6.9)          5.9	1.6 1.7 1.6 (1.2–1.8)          1.0	6.4 7.1 5.4 (5.2–6.3)          4.1
	Kulyumber, Kaya	3.20/1 3.21/1 3.23/1	poikilophytic			5.6 6.1 5.8	1.6 1.4 1.3	4.8 2.7 2.8
	Norilsk, Lama Lake	4270/5 4270/6 4270/8 4270/9 4270/12	tholeiitic poikil-ophytic tholeiitic poikiloph.			6.1 5.1 5.1 5.9 6.0	1.6 1.8 1.9 1.7 2.0	2.6 3.4 3.7 2.4 3.0
Gudchikhinsky T1sv	Kulyumber, Khalil	X-27	aphyric	Fo76-78 An60-62 CpxMg#70, Opx		8.0	1.2	4.1
	Norilsk, Lama Lake, Vologochan	75/2 Ov-6/622	porphyric porphyric	Fo78-82,An72-80, Cpx Mg#84		10.4 19.2	1.7 1.1	2.3 1.1
Khakanchansky T1hk	Kulyumber, Khalil	X-0	Vitro-classtic	Glass, Cpx, Pl		5.6	1.1	5.0
	Norilsk, Iken river	76/2a	Vitro-classtic			8.7	1.0	2.3
Tuklonsky T1tk	Norilsk, Iken river	76/1	tholeiitic	An65-78 Cpx Mg#78-84		9.3	0.9	3.0
Formation	Area, Site,	Sampe, No	(La/Sm)n	(Gd/Yb)n	(U/Nb)n	87Sr/ 86Sri	εNd	204Pb/ 208Pbi
Ivakinsky P3iv	Norilsk, Lama Lake	4270 4270/4	2.7 2.0	1.9 1.8	1.7 2.1
Syverminsky T1sv	Kulyumber, Khalil	X-3-2 X-3-3 X-28 (X-20 X-20 X-21/3 X-22 X-24 X-26) X-37 tuff	3.1 2.4 2.4 (2.3– 2.7)          2.5	1.5 1.9 1.9 (1.5– 1.8)          1.6	2.8 3.5 2.1 (2.5– 2.6)          3.0	0.70737 0.70791 0.70723	−3.1 −3.1 −3.0	18.7713 18.4227 19.2021
	Kulyumber, Kaya	3.20/1 3.21/1 3.23/1	3.3 2.3 3.6	1.8 2.0 1.9	3.2 2.0 2.6
	Norilsk, Lama Lake	4270/5 4270/6 4270/8 4270/9 4270/12	2.8 2.6 2.6 2.6 2.5	1.9 1.8 1.9 1.9 2.0	1.5 2.1 2.2 2.4 1.4
Gudchikhinsky T1sv	Kulyumber, Khalil	X-27	2.3	2.0	0.7
	Norilsk, Lama Lake, Vologochan	75/2    Ov-6/622	1.5    1.6	2.0    2.0	1.8    2.4	0.70544	3.9	18.0827
Khakanchansky T1hk	Kulyumber, Khalil	X-0	3.2	1.5	3.3
	Norilsk, Iken river	76/2a	2.1	1.5	3.2	0.70731	−2.5	18.1548
Tuklonsky T1tk	Norilsk, Iken river	76/1	2.7	1.4	4.7	0.70733	−4.5	17.7263

and

Table 7. Comparison of mineralogical and geochemical features of the intrusive rocks.

Intrusive Complex	Supposed Intrusive Complex	Area, Site, Intrusion No	Samples, No	Texture	Minerals	MgO, wt.%	TiO2, wt.%	Na2O+K2O, wt.%
Ergalakhsky	Ergalakhsky	Kulyumber Khalil, Intrusion 1	X-40 X-48	poikil- ophytic	An 39-53 Cpx Fo 42-52	3.1 3.1	2.4 2.4	5.4 5.3
Katangsky	Kyreysky	Kulyumber, Khalil, Khakil Intrusion 2	(X-7, X-8, X-18, X-19,X-25,X-35)	poikil-ophytic doleritic,	Fo 49-56 An Cpx Opx	5.0–7.4	1.3–1.6 1.8	3.1–5.0
Katangsky	Katangsky	Kulyumber, Khalil, Intrusion 4	X-6 X-15		An56-70 Cpx Mg # 53-73Fo43Opx Mg #58-69	6.5	1.6	3.9
Norilsk-type	Katangsky	Kulyumber, Khalil, Intrusion 3	X-29- X-34, X-43 X-44			7.9–8.6	0.9–1.0	2.3–2.4
Kyreysky	Kyreysky	Kureysky, Dzhaltulsky	OKG-13, T-3,4		Fo 72-73 Cpx Mg# 77-78	8.8–27.1	0.4–0.6	0.6–2.1
Norilsk	Norilsk	Norilsk, Norilsk 1	DM- 27		Fo 46-80 CpxMg# 76-84	4.5–24.5	0.6–1.2	1.4–5.5
Intrusive Complex	Supposed Intrusive Complex	Area, Site, Intrusion No	Samples, No	(La/Sm)n	(Gd/Yb)n	(U/Nb)n	(LaYb)n	Intrusive Complex
Ergalakhsky	Ergalakhsky	Kulyumber Khalil, Intrusion 1	X-40 X-48	2.5 2.6	1.8 1.9	1.5 1.5	7.9 7.9	Ergalakhsky
Katangsky	Kyreysky	Kulyumber, Khalil, Khakil Intrusion 2	(X-7, X-8, X-18, X-19,X-25X-35)	1.5–1.8	1.2–1.4	2.7–4.6	1.8–2.7	Katangsky
Katangsky	Katangsky	Kulyumber, Khalil, Intrusion 4	X-6	1.4	1.3	4.5	1.9	Katangsky
Norilsk-type	Katangsky	Kulyumber, Khalil, Intrusion 3	X-29-X-34, X-43, X-44	1.4–1.6	1.3–1.4	1.6–2.2	2.1–2.5	Norilsk-type
Kyreysky	Kyreysky	Kureysky, Dzhaltulsky	OKG-13, T-3,4	1.5–1.6	1.2–1.3	1.5–2.9	1.9–2.3	Kyreysky
Norilsk	Norilsk	Norilsk, Norilsk 1	DM- 27	1.5–1.8	1.3	3.3–4.5	1.8–2.0	Norilsk

).

Fabric of the intrusive rocks belonging to different complexes are similar and are typical of the igneous rocks crystallized near the surface (subvolcanic bodies). Poikilophytic texture dominates and dolerite texture is widespread. Compositions of rock-forming minerals reflect the composition of primary magmas that formed the intrusive bodies. The most magnesium minerals (olivines, pyroxens) are typical of the intrusions with high MgO contents, i.e., Norilsk 1 and Dzhaltulsky massifs. Plagioclases demonstrate a huge range of compositions, so the comparison of different intrusive bodies in the respect of this mineral needs a large number of analyses. We believe that chemical compositions of rocks allow better to distinguish intrusions.

The composition of major elements in the intrusions demonstrates the essential difference between the Ergalakhsky complex and the other rocks. The intrusion of the Ergalakhsky complex contains very low MgO (3.1wt.%) and high TiO₂ (2.4 wt.%) and alkalis (5.4 wt.%). Three intrusions have similar compositions in respect of these elements (high MgO, low TiO₂ and Na₂O + K₂O), they are the Norilsk 1 intrusion, the Dzhaltulsky massif. Although the Intrusion 3 in the Khalil site is not differentiated, we referred it to the Norilsk complex based on major elements contents. The Intrusion 2 preliminary attributed to the Kureysky complex differs from the Dzhaltulsky massif (standard object of this complex) in lower MgO and higher TiO₂ and it is close to the Katangsky complex (Intrusion 4) in respect of these elements. The comparison of the studied intrusive bodies in trace elements shows the principle difference between the Ergalakhsky complex and the other complexes as well. The rocks of the Ergalakhsky complex are characterized by very high Gd/Yb and especially La/Yb ratios reflecting the patterns inclination to X axis. The rocks of the other complexes have no such dramatical differences and form one range of compositions with varying characteristics (trace element ratios). There is no intrusive bodies in the Kulyumber river valley which is in a good correlation with the Dzhaltulsky massif. We concluded that the intrusions preliminary attributed to the Kureysky complex are similar to the intrusions of the Katangsky complex.

This aspect of the subdivision of magmatic rocks in the Kulyumber river valley will be regarded in the next part of the article where many intrusions of the Katangsky complex are widespread.

6.3. Magmatic Evolution

The geochemistry of igneous rocks located within the Kulyumber area demonstrates their origin from two principally different primary magmas. The first type of magmas has a mantle source which produced the volcanic rocks of the Gudchikhinsky formation. These rocks are characterized by high MgO content in comparison with the other volcanic rocks and absence of Ta-Nb negative and Pb positive anomalies, high εNd (+4) and low ⁸⁷Sr/⁸⁶Sr (0.704). These isotope characteristics allow to attribute the Gudchikhinsky rocks to products of mantle magmas. We previously studied the compositions of these magmas in the Gudchikhinsky picrites of the Norilsk area on the basis of data on melt inclusions in olivines [27]. We highlighted that the magma composition changes from the east to the west in the Norilsk area varying from a primitive mantle composition to a mantle enriched in the crustal material (up to 10%). The parental magma contains 12–14 wt.% MgO and was undersaturated in water. It crystallized near surface at T−1200 °C. Based on high Ni in olivine it was suggested that pyroxenite was a source for this magma [36]. The Gudchikhinsky basalts of the Kulymber valley river show similar geochemical features of the rocks of the Norilsk area but they enriched in LREE (La, Sm especially) and contain very low U and Th. Thus, there is an evolution of magma composition not only in sub latitudinal direction but also in sub meridional from the Norilsk area to the Kulyumber river. This type of magma is an analog of the Hawaiian tholeiites and represent an OIB source (Ocean Island Basalts) [27]. There was not found intrusive analogs of the Gudchikhinsky volcanic rocks within the Khalil and Kaya sites while they were found in the Norilsk area (the Fokinsky intrusive complex [31]).

The second type of magmas is substantially different from that which formed the Gudchikhinsky rocks. These type of magmas combines magmas of many volcanic and intrusive rocks in the Kulyumber area. It is characterized by negative Ta-Nb, positive Pb anomalies and very low εNd (up to −4) and high ⁸⁷Sr/⁸⁶Sr (reaching up 0.707) that reflect a crustal origin (WPB). It was suggested [29,30,31,32] that a sublithospheric mantle contaminated by the crust material (at 25–30 wt.%) is the source magma for these rocks. We recognized two different rock groups formed by this way. The first group combine the Syverminsky trakhybasalts and Ergalakhsky intrusive rocks while the second group comprises the volcanic rocks of the Khakanchansky, Tuklonsky and Nadezhdinsky formations and intrusions of the Katangsky, Kureysky and Norilsk complexes. The rocks of the second group were crystallized from tholeiitic magmas of normal or with relevantly high magnesium (MgO = 6−8 wt.%) at T—1200–1250 °C and contain <1% H₂O [70,71]. The magmas that formed the intrusions in the Kulyumber river valley are characterized by high TiO₂ (1.3–2.0) in comparison with the magmas of the Norilsk area where only the Daldykansky rocks have similar TiO₂ contents. During the magmatic evolution the TiO₂ content increased with time in the Norilsk area (as shown by the volcanic rock sequence, [72] and, partially by the intrusive rocks). On the basis of these data we suggest that the intrusive bodies of the Kulyumber area were formed at the end of the magmatic evolution within the Siberian platform while volcanic rocks are in good agreement with the volcanic rocks of the Norilsk are and coeval with them.

Thus, we suggest the occurrence of both type of magmatism–rift (OIB) and platform (WPB) in the Kulyumber area.

7. Conclusions

• Geochemical and mineralogical data on the volcanic rocks in the Khalil and Kaya sites of the Kulyumber area allow their attribution to the Syverminsky, Gudchikhinsky, Khakanchansky, Tuklonsky and Nadezhdinsky formations. No rocks of the Ivakinsky formation were found in the studied area, which pinches out to the south from the Norilsk area. Thus, volcanic rocks of the Syverminsky formation overlap sub-concordantly the terrigenous deposits of the Tunguska Group.
• The composition of the Guchikhinskiy formation changes from the Norilsk district to the Kulyumber river valley: rocks are enriched in alkalis (up to 4.3 wt.% in total) in the Khalil area (in comparison with 1.15% in the Norilsk area) and depleted in the Th and U contents, respectively. These data reflect an evolution of the formation within the Norilsk–Igarka paleo rift zone.
• Four intrusive complexes were recognized within the Khalil area, including Ergalakhsky, Kureysky, Katangsky and Norilsk. The latter is represented by one dyke-like body of gabbro-dolerites attributed to the Norilsk complex on the basis of it low TiO₂ and high Cr contents although the (U/Nb)n ratio is low.

A detailed analysis of intrusive rocks and discussion on their origin is given in the second part of the article devoted to the study of rocks of the southern part of the territory (the Kulyumber site), where igneouse products dominate over volcanic. The petrographic and geochemical study allowed their better attribution to the various intrusive complexes recognized in this area of the Siberian province.