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Article

Mafic Intrusions in the Cuona Area, Eastern Tethyan Himalaya: Early Kerguelen Mantle Plume Activity and East Gondwana Rifting

by
Chunxi Shan
1,
Zhiqiang Kang
1,2,*,
Feng Yang
1,2,
Chengyou Ma
1,
Zedong Qiao
1,
Zonghao Liu
1,
Jizhong Mu
1,
Lingling Wu
1 and
Lu Zhou
1
1
School of Earth Sciences, Guilin University of Technology, Guilin 541004, China
2
Collaborative Innovation Center for Exploration of Concealed Deposits and Development of Materials in Nonferrous Metals, Guilin University of Technology, Guilin 541004, China
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(3), 281; https://doi.org/10.3390/min15030281
Submission received: 15 January 2025 / Revised: 20 February 2025 / Accepted: 26 February 2025 / Published: 10 March 2025
(This article belongs to the Special Issue Tectonic Evolution of the Tethys Ocean in the Qinghai–Tibet Plateau)
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Abstract

:
The widespread occurrence of Mesozoic ocean island basalt (OIB)-like igneous rocks in the Southern Tibetan Himalayan Belt provides important constraints on the rifting of East Gondwana. This study undertook a petrological, geochronological, and geochemical investigation of mafic intrusive rocks in the Cuona area of the eastern Tethyan Himalayan Belt. The mafic intrusions have OIB-type geochemical signatures, including diabase porphyrite, gabbro, and diabase. Zircon U–Pb dating indicates that the diabase porphyrite formed at 135.0 ± 1.6 Ma. The diabase porphyrite and gabbro are enriched in high-field-strength elements (Nb and Ti) and large-ion lithophile elements (Sr and Pb) and experienced negligible lithospheric mantle or crustal contamination. The diabase is enriched in large-ion lithophile elements (LILEs, e.g., La and Ce) and depleted in high-field-strength elements (HFSEs, e.g., Ru, Zr and Ti). In general, the mafic intrusions exhibit significant light REE enrichment and heavy REE depletion and have no Eu anomalies. Whole-rock neodymium (εNd(t) = 1.55) and zircon Hf (εHf(t) = 0.60–3.73) isotopic compositions indicate derivation of the magma from enriched type I mantle. We propose that the diabase porphyrite and diabase formed in a continental margin rift setting, influenced by the Kerguelen mantle plume, and represent magmatism related to the breakup of East Gondwana. However, the gabbro formed in a relatively stable continental intraplate environment, likely derived from deep magmatic processes associated with the Kerguelen mantle plume. Our results provide new constraints on the early activity of the Kerguelen mantle plume and offer insights into the breakup and tectonic evolution of East Gondwana.

1. Introduction

The Tethyan Himalayan Belt is a key geological unit of the Tibetan Plateau and records continental rifting, lithospheric thinning, and mantle plume activity [1,2,3,4,5,6,7,8,9,10,11]. Mantle plume activity links large igneous provinces (LIPs) and the rifting of (super)continents [12]. The Kerguelen mantle plume was one of the largest mantle plumes in Earth history and had a significant role in volcanic activity in the central Indian Ocean and rifting of East Gondwana [13,14,15,16,17,18] (Figure 1a). As such, the Kerguelen mantle plume has been a focus of research. Some studies have suggested that during the Early Cretaceous, the Kerguelen mantle plume may have accelerated the rifting of East Gondwana, leading to the subsequent separation of the Indian, Australian, and Antarctic plates [13,16].
The Tethyan Himalayan Belt contains extensive Late Jurassic to Early Cretaceous mafic igneous rocks, which can be broadly classified into three types: ocean island basalts (OIBs), normal-type mid-ocean ridge basalts (N-MORBs), and transitional rocks. These rocks generally formed in a tectonic setting characterized by lithospheric extension and thinning along the northern margin of Gondwana [19,20,21,22,23,24]. OIB-type mafic rocks are considered to be the products of rifting of the East Gondwana continent and provide key insights into the regional magmatism and tectonic evolution [25,26,27,28,29]. Previous studies have suggested that an extensional tectonic setting existed during the Early Cretaceous in both the eastern and western segments of the Tethyan Himalayan tectonic belt [30]. However, the petrogenesis and tectonic setting of igneous rocks in this region are debated. Some studies have proposed that Early Cretaceous mafic magmatism in the eastern Tethyan Himalayan Belt was closely associated with the Kerguelen mantle plume, suggesting the plume was the primary driver of rifting in East Gondwana [15,25,27,30,31,32,33]. In contrast, other studies have proposed that the Early Cretaceous magmatism resulted from partial melting of enriched asthenospheric mantle, with no direct connection to the Kerguelen mantle plume. In this case, rifting of East Gondwana was driven primarily by passive rifting between the Indian and Australian–Antarctic plates [7,26,27,28,29,30,31,32,33,34].
To better understand the formation of mafic intrusions in this region and the relationship between the Kerguelen mantle plume and rifting of East Gondwana, we undertook a petrological, geochronological, and geochemical study of mafic intrusions in the Cuona area of the eastern Tethyan Himalayan Belt. By determining the ages, sources, and tectonic settings of the intrusions, we provide new constraints on the early activity of the Kerguelen mantle plume and the rifting and tectonic evolution of East Gondwana.
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Figure 1. (a) Distribution of igneous rocks related to the Kerguelen mantle plume in the Indian Ocean and adjacent continental margins [2,4,31]. (b) Geological map of the Tethyan Himalaya and adjacent areas [35,36]. (c) Geological map of the Cuomei large igneous province showing the distribution of igneous rocks with ages of >130 Ma [10,16].
Figure 1. (a) Distribution of igneous rocks related to the Kerguelen mantle plume in the Indian Ocean and adjacent continental margins [2,4,31]. (b) Geological map of the Tethyan Himalaya and adjacent areas [35,36]. (c) Geological map of the Cuomei large igneous province showing the distribution of igneous rocks with ages of >130 Ma [10,16].
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2. Geological Setting and Sample Descriptions

The Himalayan Orogenic Belt was part of the Rodinia and Gondwana supercontinents and has experienced both convergent and passive continental margin tectonism [37,38]. The Himalayan Orogenic Belt is divided into the Tethyan Himalaya, Great Himalaya, and Lesser Himalaya [35]. The Tethyan Himalayan Belt is the northernmost tectonic unit of the Himalayan Orogenic Belt and is located south of the Yarlung Zangbo Suture Zone and north of the High Himalayan Belt. The Tethyan Himalayan Belt is E–W-trending (Figure 1b). The Tethyan Himalaya consists primarily of Paleozoic–Mesozoic marine sedimentary rocks, within which mafic volcanic rocks are widely developed. The magmatism in this region occurred mainly from the Permian to Cretaceous [39,40]. The Tethyan Himalayan Belt can be divided into southern and northern zones. The southern zone consists of weakly metamorphosed sedimentary rocks from the Indian continental margin, while the northern zone is characterized by deep-water sedimentary rocks, including flysch and ophiolitic fragments.
Igneous rocks are widely distributed in the Tethyan Himalayan Belt and mainly intrude Triassic, Jurassic, and Lower Cretaceous sedimentary rocks. The igneous rocks consist mainly of basaltic volcanic rocks, diabase dikes/sills, and gabbroic intrusions, which are typically exposed in an E–W-trending belt. The study area is located in the Cuona region of the eastern Tethyan Himalaya (Figure 1c). Jurassic and Cretaceous sedimentary rocks interlayered with volcanic rocks are widely distributed in this region, occurring in the Middle to Upper Jurassic Zhela, Lure, and Sangxiu formations. The Zhela Formation consists mainly of siltstone, black shale, and graywacke interlayered with chert, limestone, and volcanic rocks. The Lure Formation is dominated by dark gray muddy (micritic) limestone, which is locally interlayered with basalt, as well as dark gray calcareous silty slate interbedded with dark gray, muddy, fine-grained limestone.
Seven samples were collected from near Juela Township in Cuona County, within the eastern Tethyan Himalayan Belt; the main rock types are diabase porphyrite (21CN-01, 21CN-02, 21CN-04, 21CN-08), gabbro (21CN-06), and diabase (21CN-07-1, 21CN-07-2) (Figure 2). The samples were collected from mafic dikes in the Lure and Zhela formations. Field investigations revealed that these intrusions have clear intrusive contacts and are extensively exposed at the surface (Figure 3a–c).
The diabase porphyrite has gray–green fresh surfaces and weathers to a light brown color (Figure 3d). It is characterized by a diabasic texture and massive structure. The primary minerals are plagioclase (~50 vol.%) and clinopyroxene (~35 vol.%). Plagioclase occurs mainly as subhedral–euhedral lath-like and tabular crystals that exhibit significant alteration, with some grains being opaque due to sericitization and chloritization. These crystals display oscillatory zoning visible under polarized light, suggesting rapid crystallization from a magmatic melt. Some plagioclase grains show fine-grained sericite filling the interstitial spaces between crystals, indicating low-temperature alteration. Clinopyroxene forms anhedral granular to short prismatic crystals that exhibit chloritization. The groundmass consists mainly of microcrysts of plagioclase, pyroxene, and biotite. Minor minerals include quartz and amphibole, with quartz appearing as small, subhedral grains often found in the interstitial spaces. Accessory minerals include magnetite, which forms opaque grains, and apatite, which appears as fine, needle-like crystals (Figure 3g).
The gabbro has dark gray fresh surfaces and weathers to a yellow–brown color (Figure 3e). It is characterized by a gabbroic texture and massive structure. The primary minerals are plagioclase (~45 vol.%) and clinopyroxene (~40 vol.%). Plagioclase is commonly subhedral, altered to clay minerals, and has a patchy texture indicative of replacement by K-feldspar. Clinopyroxene typically occurs as subhedral–anhedral, short–prismatic crystals that are interstitial to plagioclase and exhibit partial chloritization. The accessory minerals are magnetite, titanite, and apatite, which occur as irregular or acicular crystals that are randomly distributed. Micro-cracks are well developed and infilled with crystalline quartz and carbonate veinlets (Figure 3h). Additionally, some clinopyroxene crystals display distinct edge alteration features, which may be related to compositional exchange during the crystal growth process. The plagioclase shows some degree of fractures and altered textures, which may suggest that the rock has undergone an alteration process, such as weathering or hydrothermal alteration. Some titanite crystals exhibit a subtle metallic luster, which may reflect the high-temperature environment in which they formed.
The diabase has grayish blue fresh surfaces and weathers to a yellow–brown color (Figure 3f). It has a diabasic texture and massive structure. The primary mineral is plagioclase (~55 vol.%), which is subhedral–euhedral and exhibits significant alteration, including chloritization, carbonatization, and silicification. Some plagioclase microcrysts are irregularly arranged, indicative of variable degrees of alteration. These crystals dis- play oscillatory zoning, visible under polarized light, suggesting rapid crystallization from a magmatic melt. Secondary minerals include chlorite and calcite, and accessory minerals are magnetite and apatite (Figure 3i). Magnetite occurs as opaque, subhedral to anhedral grains, while apatite appears as fine, needle-like crystals interspersed in the groundmass. The rock also contains minor quartz, which appears as small, subhedral grains, commonly located in the interstitial spaces between plagioclase crystals.

3. Methods

3.1. Zircon U–Pb Dating

Two samples (21CN-02) was selected for zircon U–Pb dating by laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS). Zircon separation was conducted by the Shangyi Rock and Mineral Testing Technology Service Company Limited, Langfang, Hebei Province, China. Zircon mounting and cathodoluminescence (CL) imaging were undertaken by the Yujin Technology Company Limited in Chongqing, China. The analyses were carried out in the Guangxi Key Laboratory of Hidden Metallic Ore Exploration, Guilin University of Technology, Guilin, Guangxi, China. The LA–ICP–MS instrument comprised a New Wave 193 nm LA system coupled to an Agilent 7500 ICP–MS instrument. The laser was operated at a frequency of 5 Hz, and high-purity He was used as the carrier gas. A laser spot size of 32 μm was used for the analyses. Zircon ages were calculated by use of the standard zircon Plesovice (PL) as an external standard, and elemental concentrations were calibrated by use of the synthetic silicate glass standard NIST610 from the United States National Institute of Standards and Technology (NIST). Data processing was performed by use of ICP–MS DataCal 7.2 software [41], with common Pb corrected following [42]. Zircon U–Pb ages were calculated by use of concordia diagrams and weighted-mean age calculations, both using Isoplot 3.2 software [43]. The detailed instrumental operating conditions and data-processing methods were described by Wang et al., (2006) [44] and Yuan et al., (2004) [45].

3.2. Major and Trace Elements

The contents of major and trace elements in seven samples of diabase porphyry (21CN-01, 21CN-02, 21CN-04, 21CN-08), gabbro (21CN-06), and diabase (21CN-07-1, 21CN-07-2) were determined in the Key Laboratory of Guangxi Concealed Metal Ore Exploration of Guilin University of Technology. The rock samples were washed and dried, and weathered surfaces were removed. The samples were then crushed to <5 mm and ground into powder finer than 200 mesh. Major elements were analyzed by use of an alkali fusion glass bead method, with a ZSX Primus II X-ray fluorescence spectrometer. The precision of the major element analyses was better than ±10%. We determined trace elements with an Agilent 7500cx ICP–MS instrument after acid digestion, achieving a precision better than ±5%. Our analytical procedures followed Li et al., (2016) [46].

3.3. Sr–Nd Isotopes

The Sr–Nd isotopic compositions of sample (21CN-02) was determined at the Guangxi Key Laboratory of Hidden Metallic Ore Exploration, Guilin University of Technology. The samples were fully dissolved by acid digestion. Rubidium, Sr, and the rare earth elements (REEs) were separated by use of cation exchange resin, and Sm and Nd were further separated by use of HDEHP resin. The Sr and Nd fractions were analyzed with a Neptune Plus multi-collector–ICP–MS instrument. The 87Sr/86Sr and 143Nd/144Nd ratios were corrected for instrumental mass bias by normalization to 86Sr/88Sr = 0.1194 and 146Nd/144Nd = 0.7219, respectively. The details of the Sr–Nd isotopic analyses were described by Liang et al., (2003) [47].

3.4. Zircon Hf Isotopes

The Zircon Hf isotopic analysis was conducted on one sample (21CN-02) at the Guangxi Key Laboratory of Hidden Metallic Ore Exploration, Guilin University of Technology. The Hf isotopic analyses were undertaken near the zircon U–Pb dating sites. The Hf isotopic analyses were undertaken with a Neptune Plus multi-collector–ICP–MS instrument coupled to a GeoLas HD excimer ArF LA system. The laser spot diameter was set to 32 μm, and the laser frequency was 8 Hz. Crustal-model Hf isotopic ages were calculated by assuming the parental magma was derived from average continental crust. The 176Lu/177Hf ratio of 0.015 represents that of a depleted mantle source [48].

4. Results

4.1. Zircon U–Pb Ages

The zircon U–Pb dating results are presented in Table 1. The zircon grains from both samples are primarily euhedral–subhedral, with lengths of 50–100 μm, aspect ratios of 1:1 to 2:1, and prismatic shapes (Figure 4a). The U contents in the zircons from the diabase porphyrite sample (21CN-02) are 494–1050 ppm, and the Th contents are 462–1432 ppm. The Th/U ratios are 0.94–1.59, with an average of 1.17. These values are consistent with those of typical magmatic zircon.
After excluding discordant ages and those with large errors, the analyses were used to construct concordia diagrams. The weighted-mean 206Pb/238U age for sample 21CN-02 is 135.0 ± 1.6 Ma (MSWD = 0.68; n = 13) (Figure 4b).

4.2. Major and Trace Elements

The major element data are presented in Table 2. The SiO2 contents of the mafic intrusive rock samples are 49.24–51.95 wt.%. The Al2O3 contents are 10.51–15.58 wt.%, and the Na2O contents are 2.18–5.38 wt.%. The average K2O content is 0.61 wt.%, and the total alkali (K2O + Na2O) contents are 2.20–5.40 wt.%. Mg# values vary from 44.2 to 66.2. The loss-on-ignition (LOI) values are 1.26–5.42 wt.%, indicating these mafic intrusive rocks have undergone variable degrees of alteration. In a Nb/Y–Zr/TiO2 diagram, the samples plot in the subalkaline and alkaline basalt fields (Figure 5a), indicating transitional geochemical signatures between subalkaline and alkaline affinities. In an A/CNK–A/NK diagram, the samples plot in the metaluminous field (Figure 5b). Due to their relatively high alumina saturation index (A/CNK; 0.52–0.92) and Laitman index (σ; 0.76–3.77) values, the samples plot in the calc-alkaline to metaluminous fields on an AR–SiO2 classification diagram (Figure 5c), showing a trend in transition from sub-alkaline to alkaline components. In a SiO2–K2O diagram, the samples plot in the calc-alkaline to low-K (tholeiitic) fields (Figure 5d).
The trace element data are listed in Table 2. The total REE contents of the mafic intrusive rock samples range from 98.2 to 308.2 ppm. The REE patterns are light-REE-enriched (Figure 6a). The light/heavy REE ratios vary from 6.55 to 13.84, and (La/Yb)N = 4.25–13.09. δEu values range from 0.93 to 1.09, with an average of 1.02, indicating there are no significant Eu anomalies. In a primitive-mantle-normalized trace element diagram (Figure 6b), the diabase porphyrite and gabbro have similar trace element characteristics, with enrichments in high-field-strength elements (HFSEs, e.g., Nb and Ti) and large-ion lithophile elements (LILEs, e.g., Sr and Pb), similar to OIBs. The diabase is enriched in large-ion lithophile elements (LILEs, e.g., La and Ce) and depleted in high-field-strength elements (HFSEs, e.g., Ru, Zr, and Ti).

4.3. Sr–Nd Isotopes

The Sr–Nd isotopic data are listed in Table 3. The diabase has (87Sr/86Sr)i = 0.705583, (143Nd/144Nd)i = 0.512541, and εNd(t) = 1.51. The diabase porphyrite has relatively high (87Sr/86Sr)i and low εNd(t) values, with TDM ages of 1168 Ma (Figure 7).

4.4. Zircon Hf Isotopes

The in situ zircon Hf isotopic data are listed in Table 4. The diabase porphyrite has an average zircon 176Lu/177Hf value of 0.000803 (1σ; n = 14) and an average zircon 176Hf/177Hf value of 0.2828746 (1σ; n = 14), which represents the initial 176Hf/177Hf ratio, given the low Lu/Hf ratio. The εHf(t) values range from 0.60 to 3.73 (Figure 8), with TDM Hf model ages of 641–776 Ma.

5. Discussion

5.1. Ages

Zircon U–Pb dating was undertaken on two samples of mafic intrusive rock from the Cuona area in the eastern Tethyan Himalayan Belt of southern Tibet. The diabase porphyrite sample (21CN-02) has a crystallization age of 135.0 ± 1.6 Ma. The age of diabase porphyrite indicates that there is Early Cretaceous mafic magmatism in this area.
We compiled crystallization ages for Late Jurassic to Early Cretaceous mafic rocks in the Tethyan Himalayan Belt and constructed an age histogram (Figure 9). On the basis of previous studies, Late Jurassic to Early Cretaceous mafic magmatism in the Tethyan Himalayan Belt occurred mainly during 147–129 Ma. The crystallization age of the diabase porphyrite of this study (135.0 ± 1.6 Ma) is generally consistent with diabase crystallization ages (137–131 Ma) previously reported from the Cuona area [2,4]. It is also consistent with the Late Jurassic to Early Cretaceous magmatism in the Tethyan Himalayan Belt (Figure 9). Therefore, the studied mafic intrusive rocks may be the products of two distinct magmatic events. The diabase porphyrite corresponds to Late Jurassic to Early Cretaceous magmatism in the Tethyan Himalayan Belt (147–129 Ma), whereas the gabbro may represent the initial activity of the Kerguelen mantle plume during the Late Jurassic to Early Cretaceous.

5.2. Fractional Crystallization and Crustal Contamination

Alteration can complicate the use of geochemical data to constrain the petrogenesis of igneous rocks. Some trace elements in mafic rocks, such as REEs, HFSEs, and transition metals (e.g., V, Cr, and Ni), are barely affected by low-temperature alteration or weathering [55,56,57]. The mafic rock samples from the Cuona area have LOI values of 1.26–5.42 wt.%, indicating they have undergone variable degrees of alteration. Therefore, elements that are relatively immobile during alteration are used in the following discussion.
Primary magmas from a mantle source typically have high Mg# values (73–81) and elevated Cr (>1000 ppm) and Ni (>400 ppm) concentrations [58]. The studied samples have Mg# = 43.80–66.18, Cr = 14.8–451 ppm, and Ni = 6.5–259 ppm, which are lower than the values for primary mantle-derived magmas. This indicates that the samples have undergone fractional crystallization. Both Cr and Ni exhibit positive correlations with MgO (Figure 10d–e), indicative of the early fractional crystallization of olivine or clinopyroxene. δEu values of the mafic rock samples are 0.93–1.09, with an average of 1.02, indicative of no significant plagioclase fractionation. Al2O3 exhibits a negative correlation with MgO (Figure 10a), which is also indicative of little plagioclase fractionation. These results suggest the magma chemistry was affected mainly by clinopyroxene fractionation. Moreover, CaO exhibits a positive correlation with MgO and a negative correlation with SiO2 (Figure 10b,f), which is consistent with clinopyroxene fractionation being dominant. TiO2 exhibits a negative correlation with MgO (Figure 10c) because TiO2 was an incompatible element that was progressively enriched in the magma during early fractionation. As the magma evolved further, late fractional crystallization of magnetite occurred, which caused a decrease in TiO2 concentrations.
The diabase porphyrite samples have La/Ta = 18.2–24.4 and La/Sm = 2.33–3.12, while the gabbro samples have La/Ta = 17.0 and La/Sm = 2.50, indicating these rocks were not significantly contaminated by the crust or lithospheric mantle [59]. Moreover, the diabase porphyrite samples have Zr/Hf = 38.08–38.62 and Th/Ta = 1.5–2.40, while the gabbro samples have Zr/Hf = 38.13 and Th/Ta = 1.45, which are both different from typical crustal values [53,60]. The diabase samples have La/Ta = 26.1–27.6 and La/Sm = 2.80–3.06, indicative of no significant crustal contamination but some degree of lithospheric mantle contamination. In addition, the diabase samples have Zr/Hf = 38.91–40.51 and Th/Ta = 1.94–2.12, which are also markedly different from typical crustal values. In a La/Sm–La/Nb diagram (Figure 11a), all samples plot far from the crustal contamination trend line, indicative of insignificant crustal contamination. In a (Th/Ta)PM–(La/Nb)PM diagram (Figure 11b), the diabase porphyrite and gabbro samples plot near the primitive mantle field and away from the crustal field. Some diabase porphyrite and gabbro samples plot in the OIB-type igneous rock field associated with the Kerguelen mantle plume. The diabase samples plot farther away from the middle and upper crustal fields and closer to the lower crustal field. In a Nb/Yb–Th/Yb diagram (Figure 11c), the diabase porphyrite, gabbro, and diabase samples all exhibit characteristics similar to those of rocks from the Kerguelen Islands. They exhibit an overall trend towards the intraplate enrichment field, with no involvement of subduction-related or crustal materials. In a (La/Nb)PM–(Th/Nb)PM diagram (Figure 11d), the diabase porphyrite and gabbro samples plot in the Cuomei LIP field, close to the primitive mantle values. In contrast, the diabase samples plot closer to the lower crustal field, indicative of possible interactions with the lower crust.
In summary, the diabase porphyrite and gabbro show no features of crustal or lithospheric mantle contamination, and the diabase is contaminated by a certain degree of lithospheric mantle.

5.3. Magma Sources and Tectonic Setting

In a (87Sr/86Sr)i–(143Nd/144Nd)i diagram (Figure 7a), the samples plot near the field for the Kerguelen Islands and Kerguelen mantle plume. In a (87Sr/86Sr)i–εNd(t) diagram (Figure 7b), the samples plot within the fields for the Cuomei LIP and Kerguelen mantle plume and have similar isotopic compositions as the gabbro of the Lakang Formation in the southeastern Tethyan Himalayan Belt (Wang et al., 2022) [18]. In a (143Nd/144Nd)i–(176Hf/177Hf)i diagram (Figure 8b), the diabase porphyrite plots within the field for the Kerguelen Islands, and its isotopic composition is similar to that of the Cuomei LIP (Xia et al., 2012) [22], with (87Sr/86Sr)i = 0.7047 and εNd(t) = 1.5. These characteristics suggest the diabase porphyrite has similar isotopic compositions as other Early Cretaceous OIB-type mafic rocks in the Tethyan Himalayan Belt, and were associated with the Kerguelen mantle plume.
The average Zr/Nb and La/Nb ratios of the studied mafic intrusive rocks are 9.42 and 1.28, respectively, which are close to the values for EM I (Zr/Nb = 4.2–11.5 and La/Nb = 0.86–1.19). The geochemical characteristics of the samples are relatively uniform. In La–La/Nb and Nb–Nb/Th diagrams (Figure 12a,b), all samples plot in the OIB field. In a Zr/Nb–Y/Nb diagram (Figure 12c), all samples plot in the enriched mantle region. In a Ta/Yb–Th/Yb diagram (Figure 12d), the samples plot in the enriched mantle field and close to that for active continental margins. The OIB-type mafic intrusions in this region have EM I geochemical features, similar to other such rocks in several locations within the Tethyan Himalayan Belt in southern Tibet [19,24,29].
In Zr–Zr/Y and Zr–TiO2 diagrams, all the samples plot in the intraplate basalt field (Figure 13a,b). In a Ta/Hf–Th/Hf tectonic discrimination diagram, the diabase porphyrite samples plot in the initial rift basalt field, the gabbro samples plot in the oceanic intraplate basalt field (including OIBs, seamounts, transitional-type MORBs, and enriched-type MORBs), and the diabase samples plot in the boundary region between the initial and intracontinental rift fields (Figure 13c). In a 2Nb–Zr/4–Y tectonic discrimination diagram, the diabase porphyrite and diabase samples plot in the intraplate alkaline basalt + intraplate tholeiitic basalt field, while the gabbro samples plot in the intraplate alkaline basalt field (Figure 13d). Compared with previous studies, the diabase porphyrite and diabase have similar geochemical characteristics to volcanic rocks in the Sangxiu, Weimei, and Zhela formations in the eastern Tethyan Himalayan Belt [1,8]. This similarity suggests that the diabase porphyrite and diabase may have formed in a continental rift environment, while the gabbro, with its distinct composition, could potentially represent an continental intraplate environment. However, the age differences between these rock types have not been clearly established, and further investigations are needed to support these interpretations.

5.4. Geological Significance

Although most Cretaceous magmatism in East Gondwana was unrelated to the Kerguelen mantle plume, the Early Cretaceous magmatism in the Tethyan Himalayan Belt was closely associated with the plume [26,34]. Previous studies have shown that the OIB-type mafic magmatism in this tectonic belt began at ca. 147 Ma and ended at 125 Ma [2,4,5,24,29,69]. According to an Early Cretaceous paleogeographic reconstruction of Gondwana, the Tethyan Himalayan Belt was located along a passive continental margin at the time. There is a lack of arc-related igneous rocks that coexist with the Early Cretaceous OIB-type mafic rocks, which rules out the possibility of their formation in a subduction setting [70,71]. During the Late Jurassic to Early Cretaceous, the Cuona area was located along the passive continental margin of eastern Gondwana, adjacent to the Neo-Tethys Ocean. The rapid expansion of the Neo-Tethys Ocean caused intense extensional tectonism south of the mid-ocean ridge, leading to the formation of rift structures [8,27,72]. OIB-type igneous rocks are generally considered to be the products of a mantle plume or hotspot activity [73]. The Early Cretaceous OIB-type mafic rocks in the Tethyan Himalayan Belt were closely related to the Kerguelen mantle plume, which had a key role in the rifting of eastern Gondwana [16,25,28,30].
The diabase porphyrite formed at 135.0 ± 1.6 Ma, which is slightly earlier than the peak of Kerguelen mantle plume activity (ca. 132 Ma; Zhu et al., 2008; Zhu et al., 2009; Ma et al., 2016) [2,16,74], and was coeval with the Bunbury basalts (137–136 Ma) and the oceanic magnetic anomaly (136 Ma) that record the rifting of eastern Gondwana [34,75]. Furthermore, the diabase porphyrite has distinct OIB-type geochemical characteristics, with enrichments in light REEs and HFSEs, indicative of a mantle plume source. Its age coincides with the peak of mafic magmatism during the Late Jurassic–Early Cretaceous (147–129 Ma) in the Tethyan Himalayan Belt (Figure 9). Therefore, the diabase porphyrite was formed in a continental rift setting associated with the Kerguelen mantle plume, and represents a product of the rifting of eastern Gondwana.

5.5. Kerguelen Mantle Plume and Evolution of Eastern Gondwana

The initial stages of continental rifting are typically associated with LIPs [76,77]. There are differing views on the relationship between the rifting of eastern Gondwana and the Kerguelen mantle plume. Some studies have suggested there is no direct relationship between the two [26]. However, there is some evidence that the Kerguelen mantle plume had a key role in the rifting of East Gondwana. For example, the bimodal magmatism during 147–130 Ma, the formation of A-type granites [6,25], and the development of the Indian Ocean Ridge at 136 Ma were all associated with mantle plume activity. Some studies have suggested that the small magmatic provinces on East Gondwana were associated with the activity of the Kerguelen mantle plume [16,18,26,34]. The magmatism associated with the plume lasted for an extended period, with intermittent eruptions for potentially >100 Myr on both sides of the Southeast Indian Ridge [78]. These lines of evidence suggest that the prolonged magmatic activity of the Kerguelen mantle plume played a key role in the rifting of East Gondwana and potentially caused the rifting.
As East Gondwana began to rift, the Indian Plate gradually moved northward, and the Kerguelen mantle plume activity became increasingly focused in the Tethyan Himalayan region. At ca. 147 Ma, East Gondwana underwent initial rifting and the Cuona area in the eastern Tethyan Himalayan Belt was located in the central part of the Kerguelen mantle plume head (Figure 14a; Zhang et al., 2023) [10]. As the rifting of East Gondwana proceeded, the Cuona area began to drift towards the edge of the Kerguelen mantle plume, and the mantle plume magmatism peaked, which formed a large volume of OIB-type basalts at ca. 135 Ma (Figure 14b). With the further expansion of the mantle plume head, younger OIB-type volcanic rocks (125 Ma) formed (Dong et al., 2019) [70]. The bimodal magmatism (118–115 Ma) and N-MORB-type basalts (ca. 120 Ma) in the eastern Tethyan Himalaya are the products of extension rather than Kerguelen mantle plume activity [2,3,5,16]. Furthermore, the Australia–Antarctic plate had a relatively stable paleo-latitude during 140–120 Ma (Torsvik et al., 2012) [79], indicating the Indian Plate had completely separated from East Gondwana by ca. 125 Ma (Figure 14c).
Our results indicate that early activity of the Kerguelen mantle plume not only facilitated the rifting of East Gondwana, but also affected the tectonic and magmatic evolution of the Tethyan Himalaya. Our study has provided new constraints on the early activity of the Kerguelen mantle plume, which had a key role in the geological evolution of the Tethyan Himalaya, and the origins of basaltic magmatism in continental margin rift and intraplate settings during the rifting of East Gondwana.

6. Conclusions

We investigated the petrology, geochronology, and geochemistry of mafic intrusive rocks in the Cuona region of the eastern Tethyan Himalaya. Our main conclusions are as follows:
(1)
The diabase porphyrite formed in the Early Cretaceous (135.0 ± 1.6 Ma). The diabase porphyrite and gabbro have a similar petrogenesis to the numerous OIB-type mafic igneous rocks in the Cuomei LIP, displaying typical OIB-type geochemical signatures without contamination by lithospheric mantle or crust. These rocks were likely derived from EMI-like enriched mantle. The diabase porphyrite formed in a continental rift setting related to the Kerguelen mantle plume, whereas the gabbro should be the product of the deep magma of the Kerguelen mantle plume in a stable continental intraplate environment.
(2)
The mafic intrusive rocks in the Cuona region are subalkaline to alkaline. There is significant fractionation between the light (enriched) and heavy (depleted) REEs and no significant Eu anomalies. The trace element characteristics of the diabase porphyrite and gabbro are similar, with both being enriched in HFSEs and LILEs. The diabase is enriched in large-ion lithophile elements (LILEs, e.g., La and Ce) and depleted in high-field-strength elements (HFSEs, e.g., Ru, Zr and Ti).
(3)
The age of the diabase porphyrite (135 Ma) is slightly older than the peak of Kerguelen mantle plume activity (132 Ma), indicating it was the product of East Gondwana continental rifting associated with the effects of the Kerguelen mantle plume.

Author Contributions

Conceptualization, F.Y. and C.M.; methodology, Z.Q.; software, Z.L.; validation, F.Y.; formal analysis, J.M.; investigation, Z.L.; resources, L.W.; data curation, Z.Q.; writing—original draft preparation, C.S.; writing—review and editing, Z.K.; visualization, L.Z.; supervision, F.Y.; project administration, C.S.; funding acquisition, Z.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the following projects: The project of National Natural Science Foundation of China “The genesis of mafic rocks in the middle and eastern parts of the Tethys Himalayan belt and its constraints on the early evolution history of the Neo-Tethys Ocean”, grant number: 42173048; National Key R & D Program “Study on Comprehensive Application of Refractory Elements and Isotope Analysis Technology”, grant number: 2020YFA0714804; and the Innovation Project of Guangxi Graduate Education “Determination of the initial breakup time of the Neo-Tethys Ocean in Tibet”, grant number: YCSW2021206.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 2. Simplified geological map of the Cuona area in the eastern segment of the Tethyan Himalayan Belt (modified from the 1:50,000 Juela Geological Map).
Figure 2. Simplified geological map of the Cuona area in the eastern segment of the Tethyan Himalayan Belt (modified from the 1:50,000 Juela Geological Map).
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Figure 3. (a–c) Field photographs, (d–f) hand specimens, and (g–i) microscopic characteristics of mafic intrusions in the Cuona area. Pl = plagioclase; Cpx = clinopyroxene; Mt = magnetite; Bt = biotite; Kfs = K-feldspar; Cal = calcite; Chl = chlorite.
Figure 3. (a–c) Field photographs, (d–f) hand specimens, and (g–i) microscopic characteristics of mafic intrusions in the Cuona area. Pl = plagioclase; Cpx = clinopyroxene; Mt = magnetite; Bt = biotite; Kfs = K-feldspar; Cal = calcite; Chl = chlorite.
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Figure 4. (a) Cathodoluminescence (CL) images from mafic intrusions in the Cuona area, (b) U–Pb concordia diagrams of zircon grains from mafic intrusions in the Cuona area.
Figure 4. (a) Cathodoluminescence (CL) images from mafic intrusions in the Cuona area, (b) U–Pb concordia diagrams of zircon grains from mafic intrusions in the Cuona area.
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Figure 5. Geochemical classification diagrams for mafic intrusive rocks in the Cuona area and related rocks [49,50,51,52]. (a) Nb/Y–Zr/TiO2 diagram; (b) A/CNK–A/NK diagram; (c) AR–SiO2 classification diagram; (d) SiO2–K2O diagram. Data for regional OIB-type mafic rocks are from Zhu et al., (2008), Chen et al., (2021), and Yang et al., (2022) [2,4,29].
Figure 5. Geochemical classification diagrams for mafic intrusive rocks in the Cuona area and related rocks [49,50,51,52]. (a) Nb/Y–Zr/TiO2 diagram; (b) A/CNK–A/NK diagram; (c) AR–SiO2 classification diagram; (d) SiO2–K2O diagram. Data for regional OIB-type mafic rocks are from Zhu et al., (2008), Chen et al., (2021), and Yang et al., (2022) [2,4,29].
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Figure 6. (a) Chondrite-normalized rare earth element (REE) patterns and (b) primitive-mantle-normalized trace element diagram for mafic intrusive rocks in the Cuona area and related rocks (chondrite, primitive mantle, OIB, N-MORB, and E-MORB data are from Sun and McDonough, 1989 [53]; OIB-type mafic rock data associated with the Kerguelen mantle plume are from Zhu et al., 2008; Chen et al., 2021; Yang et al., 2022) [2,4,29].
Figure 6. (a) Chondrite-normalized rare earth element (REE) patterns and (b) primitive-mantle-normalized trace element diagram for mafic intrusive rocks in the Cuona area and related rocks (chondrite, primitive mantle, OIB, N-MORB, and E-MORB data are from Sun and McDonough, 1989 [53]; OIB-type mafic rock data associated with the Kerguelen mantle plume are from Zhu et al., 2008; Chen et al., 2021; Yang et al., 2022) [2,4,29].
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Figure 7. (a) (87Sr/86Sr)i versus (143Nd/144Nd)i and (b) (87Sr/86Sr)i versus εNd(t) diagrams for mafic intrusive rocks in the Cuona area and related rocks (Kerguelen mantle plume, Kerguelen Islands, Kerguelen Plateau, Ninetyeast Ridge, and Rajmahal–Bengal–Sylhet Traps data are from Olierook et al., 2019; Peng et al., 2022; gabbro data are from Wang et al., 2022) [8,18,26].
Figure 7. (a) (87Sr/86Sr)i versus (143Nd/144Nd)i and (b) (87Sr/86Sr)i versus εNd(t) diagrams for mafic intrusive rocks in the Cuona area and related rocks (Kerguelen mantle plume, Kerguelen Islands, Kerguelen Plateau, Ninetyeast Ridge, and Rajmahal–Bengal–Sylhet Traps data are from Olierook et al., 2019; Peng et al., 2022; gabbro data are from Wang et al., 2022) [8,18,26].
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Figure 8. (a) Zircon εHf(t) and (b) (143Nd/144Nd)i–(176Hf/177Hf)i diagrams for mafic intrusive rocks in the Cuona area and related rocks (Kerguelen Islands and Tethyan Himalayan Igneous Province data are from Chen et al., 2018 and Chen et al., 2021) [3,4].
Figure 8. (a) Zircon εHf(t) and (b) (143Nd/144Nd)i–(176Hf/177Hf)i diagrams for mafic intrusive rocks in the Cuona area and related rocks (Kerguelen Islands and Tethyan Himalayan Igneous Province data are from Chen et al., 2018 and Chen et al., 2021) [3,4].
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Figure 9. Histogram of ages for Late Jurassic to Early Cretaceous mafic rocks in the Tethyan Himalaya (age data are from Zhu et al., 2009; Hou Chenyang, 2017; Shi et al., 2017; Chen et al., 2021; Deng Jin, 2021; Liang et al., 2023) [4,16,36,54].
Figure 9. Histogram of ages for Late Jurassic to Early Cretaceous mafic rocks in the Tethyan Himalaya (age data are from Zhu et al., 2009; Hou Chenyang, 2017; Shi et al., 2017; Chen et al., 2021; Deng Jin, 2021; Liang et al., 2023) [4,16,36,54].
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Figure 10. Major elements variation diagram for mafic rocks from the Cuona area. (a) MgO-Al2O3 diagram; (b) MgO-CaO diagram; (c) MgO-TiO2 diagram; (d) MgO-Cr diagram; (e) MgO-Ni diagram; (f) SiO2-CaO diagram.
Figure 10. Major elements variation diagram for mafic rocks from the Cuona area. (a) MgO-Al2O3 diagram; (b) MgO-CaO diagram; (c) MgO-TiO2 diagram; (d) MgO-Cr diagram; (e) MgO-Ni diagram; (f) SiO2-CaO diagram.
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Figure 11. Plots used to identify crustal contamination of mafic intrusions in the Cuona area: (a) La/Sm versus La/Nb; (b) Th/Ta versus La/Nb; (c) Nb/Yb versus Th/Yb; (d) (La/Nb)PM versus (Th/Nb)PM [1,2,34]. Data sources: upper, middle, and lower crust [61]; primitive mantle [62]; lithospheric mantle [63]; OIB-type igneous rocks related to the Kerguelen mantle plume [1]. OIB = ocean island basalt; E-MORB = enriched mid-ocean ridge basalt; N-MORB = normal mid-ocean ridge basalt; UC = upper crust; MC = middle crust; LC = lower crust; PM = primitive mantle; CLM = continental lithospheric mantle.
Figure 11. Plots used to identify crustal contamination of mafic intrusions in the Cuona area: (a) La/Sm versus La/Nb; (b) Th/Ta versus La/Nb; (c) Nb/Yb versus Th/Yb; (d) (La/Nb)PM versus (Th/Nb)PM [1,2,34]. Data sources: upper, middle, and lower crust [61]; primitive mantle [62]; lithospheric mantle [63]; OIB-type igneous rocks related to the Kerguelen mantle plume [1]. OIB = ocean island basalt; E-MORB = enriched mid-ocean ridge basalt; N-MORB = normal mid-ocean ridge basalt; UC = upper crust; MC = middle crust; LC = lower crust; PM = primitive mantle; CLM = continental lithospheric mantle.
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Figure 12. (a) La versus La/Nb ((a) is from Shuguang Li, 1993) [64], (b) Nb versus Nb/Th ((b) is from Shuguang Li, 1993) [64], (c) Zr/Nb versus Y/Nb ((c) is from Wilson, 1997) [58], and (d) Ta/Yb versus Th/Yb diagrams ((d) is from Meschede, 1986) [65] for mafic intrusive rocks in the Cuona area. OIB = ocean island basalt; MORB = mid-ocean ridge basalt; IAB = island arc basalt; N-MORB = normal mid-ocean ridge basalt; CLM = continental lithospheric mantle.
Figure 12. (a) La versus La/Nb ((a) is from Shuguang Li, 1993) [64], (b) Nb versus Nb/Th ((b) is from Shuguang Li, 1993) [64], (c) Zr/Nb versus Y/Nb ((c) is from Wilson, 1997) [58], and (d) Ta/Yb versus Th/Yb diagrams ((d) is from Meschede, 1986) [65] for mafic intrusive rocks in the Cuona area. OIB = ocean island basalt; MORB = mid-ocean ridge basalt; IAB = island arc basalt; N-MORB = normal mid-ocean ridge basalt; CLM = continental lithospheric mantle.
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Figure 13. (a) Zr/Y versus Zr ((a) is from Pearce and Norry, 1979) [66], (b) Zr versus Ti ((b) is from Pearce, 1982) [67], (c) Th/Hf versus Ta/Hf ((c) is from Wang et al., 2001) [68], and (d) 2Nb–Zr/4–Y tectonic discrimination diagrams ((d) are from Meschede, 1986) [65] for mafic intrusive rocks in the Cuona area. WPB = within-plate basalt; IAB = island arc basalt; MORB = mid-ocean ridge basalt; A1 = within-plate alkaline basalts; A2 = within-plate alkaline basalts + within-plate tholeiites; B = E-MORBs; C = within-plate tholeiites + volcanic arc basalts; D = volcanic arc basalts + E-MORBs.
Figure 13. (a) Zr/Y versus Zr ((a) is from Pearce and Norry, 1979) [66], (b) Zr versus Ti ((b) is from Pearce, 1982) [67], (c) Th/Hf versus Ta/Hf ((c) is from Wang et al., 2001) [68], and (d) 2Nb–Zr/4–Y tectonic discrimination diagrams ((d) are from Meschede, 1986) [65] for mafic intrusive rocks in the Cuona area. WPB = within-plate basalt; IAB = island arc basalt; MORB = mid-ocean ridge basalt; A1 = within-plate alkaline basalts; A2 = within-plate alkaline basalts + within-plate tholeiites; B = E-MORBs; C = within-plate tholeiites + volcanic arc basalts; D = volcanic arc basalts + E-MORBs.
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Figure 14. Model of the evolution of the Kerguelen mantle plume and East Gondwana (modified from Gibbons et al., 2013; Olierook et al., 2019; Wang et al., 2022; Liang et al., 2023) [9,18,26,77]. (a) At ca. 147 Ma, East Gondwana underwent initial rifting and the Cuona area in the eastern Tethyan Himalayan Belt was located in the central part of the Kerguelen mantle plume head. (b) At ca. 135 Ma, as the rifting of East Gondwana proceeded, the Cuona area began to drift towards the edge of the Kerguelen mantle plume, and the mantle plume magmatism peaked, which formed a large volume of OIB-type basalts. (c) By ca. 125 Ma, the Indian Plate had completely separated from East Gondwana, as indicated by the paleo-latitude stability of the Australia–Antarctic Plate.
Figure 14. Model of the evolution of the Kerguelen mantle plume and East Gondwana (modified from Gibbons et al., 2013; Olierook et al., 2019; Wang et al., 2022; Liang et al., 2023) [9,18,26,77]. (a) At ca. 147 Ma, East Gondwana underwent initial rifting and the Cuona area in the eastern Tethyan Himalayan Belt was located in the central part of the Kerguelen mantle plume head. (b) At ca. 135 Ma, as the rifting of East Gondwana proceeded, the Cuona area began to drift towards the edge of the Kerguelen mantle plume, and the mantle plume magmatism peaked, which formed a large volume of OIB-type basalts. (c) By ca. 125 Ma, the Indian Plate had completely separated from East Gondwana, as indicated by the paleo-latitude stability of the Australia–Antarctic Plate.
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Table 1. Zircon U-Th-Pb isotopic dating results of mafic intrusive rocks in the Cuona region.
Table 1. Zircon U-Th-Pb isotopic dating results of mafic intrusive rocks in the Cuona region.
Sample PointContent/10−6Th/UIsotopic RatioIsotopic Age/Ma
PbThU207Pb/235U1σ206Pb/238U1σ207Pb/235U1σ206Pb/238U1σCon*
21CN-02-0621.77792755.0443739.77021.020.145850.006070.021590.00023138.25.4137.71.499%
21CN-02-1132.316791302.5091049.6371.240.142070.005510.021250.00025134.94.9135.51.699%
21CN-02-1414.03134462.2057493.63750.940.143180.008590.021340.00030135.97.6136.11.999%
21CN-02-1618.90271701.7517629.28321.120.141620.006950.021790.00029134.56.2138.91.896%
21CN-02-1716.85502588.0218581.09791.010.138000.006940.020940.00030131.36.2133.61.998%
21CN-02-3015.79062511.8948516.8870.990.151490.010390.021520.00037143.29.2137.22.395%
21CN-02-3130.230751272.806971.96391.310.140060.009100.020470.00025133.18.1130.61.698%
21CN-02-3330.339581412.224916.93561.540.136820.006040.021010.00024130.25.4134.11.597%
21CN-02-3424.13773930.2534796.98681.170.131950.005610.021130.00025125.95.0134.81.693%
21CN-02-3723.66793838.1252767.26041.090.137380.005660.021770.00025130.75.1138.81.693%
21CN-02-3829.240661148.345976.73211.180.134560.005500.020630.00026128.24.9131.61.697%
21CN-02-3929.712451432.31901.6371.590.139250.006040.020960.00024132.45.4133.71.598%
21CN-02-4016.04238557.4163553.46981.010.130570.006500.021030.00029124.65.8134.11.892%
Con*: Concordance.
Table 2. Major (wt.%), trace (ppm), and rare earth element (ppm) analysis results of mafic intrusive rocks from the Cuona region.
Table 2. Major (wt.%), trace (ppm), and rare earth element (ppm) analysis results of mafic intrusive rocks from the Cuona region.
Sample21CN-0121CN-0221CN-0421CN-0621CN-07-121CN-07-221CN-08
Rock typeDiabase
porphyrite		Diabase
porphyrite		Diabase
porphyrite		GabbroDiabaseDiabaseDiabase
porphyrite
Al2O313.0613.3113.7012.8213.7614.689.99
CaO7.289.6710.776.675.794.208.68
Fe2O3T11.5210.0411.0012.8013.1012.0513.17
K2O0.800.980.871.400.030.020.02
MgO6.126.626.494.284.604.0911.06
MnO0.160.150.160.200.190.180.17
Na2O3.983.202.233.154.545.072.07
P2O50.400.280.300.451.561.430.29
SiO249.0548.9549.5550.8946.3848.9446.94
TiO23.992.742.854.584.253.552.68
LOI2.743.171.262.625.424.894.90
Total99.1199.1299.1999.8799.6299.1099.93
Li18.699.9414.8013.7425.9721.0131.60
Sc35.4733.3938.3714.3918.5713.8219.99
Ti24,816.8717,116.7617,443.9628,228.7727,042.9522,586.4216,904.02
V272.22231.41247.41251.02243.71171.81242.08
Cr298.87440.10179.8614.8198.4714.96451.08
Mn1104.181066.031110.471429.791355.651174.421171.26
Co40.9739.1742.9534.3929.5823.2063.07
Ni124.74154.7967.2417.7042.626.51259.45
Cu36.8838.1326.4113.9919.8510.8332.69
Zn128.99109.63113.31127.48135.54150.72124.56
Ga25.8914.1114.0816.1116.9414.289.41
Rb17.9329.8129.6418.021.671.210.38
Sr548.45437.22578.08672.441046.50587.6279.02
Y30.2223.2525.5831.1238.7640.0125.63
Zr240.84165.96177.32275.20215.56239.69162.32
Nb20.7915.3015.4023.3129.4633.4612.94
Mo1.782.240.651.531.751.580.72
Cs0.180.320.600.311.120.480.72
Ba538.48195.03166.93236.48214.15100.3322.52
La24.4116.8918.1821.4844.3148.4113.21
Ce52.3136.3638.7652.73109.73116.7332.96
Pr6.964.875.206.5513.6714.224.58
Nd31.5122.2123.5433.3862.5372.8721.13
Sm7.845.576.098.5915.8415.835.67
Eu2.511.871.992.575.355.151.93
Gd7.625.596.088.3314.3114.205.74
Tb1.190.890.951.331.941.940.94
Dy6.645.005.467.459.719.765.47
Ho1.250.961.021.401.661.681.03
Er3.152.402.583.493.813.912.66
Tm0.410.320.350.470.450.470.37
Yb2.521.932.082.832.502.652.23
Lu0.350.270.290.390.330.350.31
Hf6.324.344.597.225.545.924.24
Ta1.000.930.791.271.701.760.61
Tl0.070.050.070.110.010.010.14
Pb2.411.532.253.013.192.752.15
Th1.881.401.891.833.293.721.34
U0.480.330.420.600.740.840.33
A/CNK0.630.560.570.680.760.920.52
A/NK1.762.102.971.911.831.762.92
AR1.611.441.291.251.611.611.74
Mg#55.3260.5857.8943.8045.0044.1766.18
FeOT10.769.4210.1111.8412.5111.5112.47
∑REE148.67105.14112.56150.98286.14308.1698.23
LREE133.1693.3799.84133.62265.73287.4085.22
HREE15.5211.7712.7317.3620.4020.7613.01
LREE/HREE8.587.937.857.7013.0213.846.55
Eu*0.991.031.000.931.091.051.04
(La/Yb)N6.966.266.285.4512.7013.094.25
(Sm/Yb)N3.463.203.253.377.036.622.83
(La/Sm)N2.011.961.931.621.811.981.51
(Tb/Yb)N2.162.102.102.143.543.341.92
Notes: AR = (Al2O3 + CaO + Na2O + K2O)/(Al2O3 + CaO-Na2O-K2O).
Table 3. Sr-Nd isotope analysis results of mafic intrusive rocks in the Cuona region.
Table 3. Sr-Nd isotope analysis results of mafic intrusive rocks in the Cuona region.
SampleSm
(ppm)		Nd
(ppm)		Rb
(ppm)		Sr
(ppm)		147Sm/144Nd143Nd/144Nd(143Nd/144Nd)iεNd(t)87Rb/86Sr87Sr/86Sr(87Sr/86Sr)iTDM(Ga)
21CN-025.5722.2129.81437.220.151710.512680.512541.550.197250.705970.705581.1668
Table 4. Lu-Hf isotope analysis results of zircons from mafic intrusive rocks in the Cuona region.
Table 4. Lu-Hf isotope analysis results of zircons from mafic intrusive rocks in the Cuona region.
Sample PointAge (Ma)176Yb/177Hf176Lu/177Hf176Hf/177Hf±2σεHf(0)εHf(t)(176Hf/177Hf)iTDM(Hf)TDM (Ma)fLu/Hf
21CN-02-021430.027420.000630.282720.000016−1.830401.305430.282727451113−0.981
21CN-02-031420.030720.000730.282730.000017−1.650961.462970.282737391102−0.978
21CN-02-041490.030140.000730.282710.000016−2.259221.008270.282717631137−0.978
21CN-02-111360.026010.000610.282780.0000180.206083.188770.28278664988−0.982
21CN-02-121400.025560.000590.282770.000016−0.169552.900890.282776781009−0.982
21CN-02-141360.023670.000550.282740.000018−1.207161.775110.282747191078−0.983
21CN-02-171340.027460.000650.282800.0000160.794273.733200.28279641951−0.980
21CN-02-191480.025740.000620.282740.000018−1.109722.136180.282747161064−0.981
21CN-02-201410.033730.000810.282710.000017−2.390560.701160.282707701150−0.976
21CN-02-311310.054260.001390.282760.000035−0.428952.443730.282767011031−0.958
21CN-02-361390.041030.000970.282760.000017−0.610202.438150.282757011038−0.971
21CN-02-381320.034650.000840.282760.000016−0.417382.477270.282766921030−0.975
21CN-02-391340.045430.001100.282770.000017−0.293322.645300.282766911021−0.967
21CN-02-401400.039280.001020.282700.000020−2.470440.599300.282707761156−0.969
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Shan, C.; Kang, Z.; Yang, F.; Ma, C.; Qiao, Z.; Liu, Z.; Mu, J.; Wu, L.; Zhou, L. Mafic Intrusions in the Cuona Area, Eastern Tethyan Himalaya: Early Kerguelen Mantle Plume Activity and East Gondwana Rifting. Minerals 2025, 15, 281. https://doi.org/10.3390/min15030281

AMA Style

Shan C, Kang Z, Yang F, Ma C, Qiao Z, Liu Z, Mu J, Wu L, Zhou L. Mafic Intrusions in the Cuona Area, Eastern Tethyan Himalaya: Early Kerguelen Mantle Plume Activity and East Gondwana Rifting. Minerals. 2025; 15(3):281. https://doi.org/10.3390/min15030281

Chicago/Turabian Style

Shan, Chunxi, Zhiqiang Kang, Feng Yang, Chengyou Ma, Zedong Qiao, Zonghao Liu, Jizhong Mu, Lingling Wu, and Lu Zhou. 2025. "Mafic Intrusions in the Cuona Area, Eastern Tethyan Himalaya: Early Kerguelen Mantle Plume Activity and East Gondwana Rifting" Minerals 15, no. 3: 281. https://doi.org/10.3390/min15030281

APA Style

Shan, C., Kang, Z., Yang, F., Ma, C., Qiao, Z., Liu, Z., Mu, J., Wu, L., & Zhou, L. (2025). Mafic Intrusions in the Cuona Area, Eastern Tethyan Himalaya: Early Kerguelen Mantle Plume Activity and East Gondwana Rifting. Minerals, 15(3), 281. https://doi.org/10.3390/min15030281

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