Search Results (19)

The Chinese Altay is located in the western segment of the Central Asian Orogenic Belt (CAOB) and preserves critical records of the Paleo-Asian Ocean (PAO) Plate evolution during the Paleozoic era. This region also hosts significant mineral deposits, making it a focal point for geological research. In this paper, field investigation, petrology, mineralogy, and petrography studies were conducted on volcanic rocks in the Fuyun–Qinghe area, southern margin of the Chinese Altay, and the paper provided new zircon LA-ICP-MS dating data, Lu-Hf isotope data, and whole-rock geochemical data of the basaltic to andesitic volcanic rocks. Thus, the formation age, petrogenesis, and tectonic setting of these rocks were discussed, which was of great significance to reveal the nature of the PAO Plate. The findings showed that the basaltic andesitic volcanic breccia was formed at 382.9 ± 3.4 Ma, the basalt was 401.7 ± 4.7 Ma, and the andesites were 405.1 ± 5.6 Ma and 404.8 ± 6.7 Ma, which indicated that the above rocks were formed in the Early–Middle Devonian. The volcanic rock assemblages were hawaiite, mugearite, potassic trachybasalt, basaltic andesite, andesite, benmoreite, etc., which contained labeled magmatic rocks such as adakite, sub-boninite, niobium-enriched arc basalt (NEAB), picrite, high-magnesium andesite (HMA), and magnesium andesite (MA). Comprehensive analysis indicated that magma probably mainly originated from three sources: (1) partial melting of the PAO slab, (2) partial melting of the overlying garnet–spinel lherzolite mantle peridotite metasomatized by subducting-related fluids (melts), and (3) a possible input of the asthenosphere. Comparative analysis with modern analogs (e.g., Chile Triple Junction) indicates that ridge subduction of the PAO had existed in the Fuyun–Qinghe area during the Early–Middle Devonian. Based on available evidence, we tentatively named the oceanic plates in this region the central Fuyun–Qinghe Ridge and the Junggar Ocean Plates, separated by the ridge on both sides. Although the ocean had a certain scale, it had entered the climax period of transition from ocean to continent. Full article

The late Permian Emeishan large igneous province (ELIP) in SW China is a melting product of the Emeishan mantle plume. Recently, it has been debated whether peridotite or pyroxenite is the dominant lithology of the mantle source in the ELIP. To address this, systematic analyses of bulk-rock and coexisting spinel and olivine compositions were conducted on picrites from Lijiang–Yongsheng, Dali–Binchuan, Yumen, Muli, and Ertan. The ELIP picrites exhibit positive TiO₂–CaO and negative MgO–CaO correlations, as well as low FC3MS values (−0.24–0.1), supporting a peridotite-dominated mantle source. This lithology of the mantle source is also supported by the high 100 × Mn–Fe (1.43–1.73) and Mn–Zn (13.6–18.4) values but low 10,000 × Zn–Fe (8.0–12.7) ratios of the olivine phenocrysts. The estimated mantle potential temperature for Lijiang, Yongsheng, Yumen–Ertan, Muli, and Dali–Binchuan picrites decreased away from Lijiang and Yongsheng, suggesting that the Lijiang and Yongsheng areas were the center of the ELIP. The Lijiang–Yongsheng primary magma shows similar SiO₂ content but lower Al₂O₃ contents (average of 8.24 wt.%) and higher MgO contents (average of 21.42 wt.%) than those of Dali–Binchuan primary magma (Al₂O₃: 9.86 wt.%; MgO: 19.02 wt.%). Also considering the high Gd–Yb (average of 3.05) and La–Yb (average of 14.61) ratios and mantle potential temperature (average of 1599 °C), we proposed that Lijiang–Yongsheng lavas are produced via the melting of a garnet–peridotitic mantle. In contrast, the Dali–Binchuan lavas with low Gd–Yb (average of 1.91) and La–Yb (average of 5.88) ratios can be explained by their formation in the garnet–spinel transition zone of a peridotitic mantle. The Yumen–Ertan primary magma displays similar mantle potential temperature (average of 1600 °C), Al₂O₃ and FeO content, and Gd–Yb ratios to those of Lijiang–Yongsheng lavas, indicating that YumenvErtan primary magma may be attributed to the partial melting of garnet with minor peridotite. Therefore, heterogeneous plume-head mantle sources lead to the evaluation of melting conditions of the late Permian ELIP picrites. Full article

Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of ²⁰⁸Pb/²⁰⁴Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic ²⁰⁸Pb/²⁰⁴Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume. Full article

The Kresty volcano–plutonic complex (KVPC) is one of the representatives of the alkaline–ultrabasic magmatism in the Maymecha-Kotuy Alkaline Province in Polar Siberia. The geological structure of the KVPC consists of intrusive formations of olivinite–pyroxenite and melilitolite–monticellitolite bodies, a series of rocks that break through dikes of trachydolerites, syenites, granosyenites, alkaline picrites and lamprophyres. This paper summarizes the results of the authors’ long-term research on the geological structure and features of the material composition of the intrusive magmatic rocks, including geochemistry, mineralogy, distribution of rare earth elements (REE), as well as the results of isotope studies. The multielement composition of the KVPC intrusions demonstrates a complex geodynamic paleoenvironment of the formation as plume nature with signs of subduction and collision. For the ultrabasic series with normal alkalinity from the first phase of the KVPC, a Sm-Nd isochron age yielded an Early Triassic (T₁) result of 251 ± 25 Ma. Here, we present U-Pb dating of zircons and perovskite of high-calcium intrusive formations and a dyke complex of alkaline syenites. Thus, for the intrusion of kugdite (according to perovskite), the age determination was 249 ± 4 Ma, and for the crosscutting KVPC dykes of syenites (according to zircon) 249 ± 1 Ma and 252 ± 1 Ma. The age of the most recent dike is almost identical to the age of the main intrusive phases of the KVPC (T₁), which corresponds to a larger regional event of the Siberian LIP—251 Ma. According to isotopic Sr-Nd parameters, the main source of KVPC magmas is a PREMA-type material. For dyke varieties, we assume there was an interaction of plume melts with the continental crust. The new age results obtained allow us to further constrain the episodes of alkaline–ultrabasic intrusions in Polar Siberia, taking into account the interaction of mantle plume matter and crustal material. Full article

The Shatak Formation, comprising a part of the Mashak Suite (RF₂), is located on the western slope of the Southern Urals. It consists of various rock types, including sedimentary rocks, such as conglomerates, polymictic sandstones, aleurolites, and carbonaceous clayey shales, as well as igneous rocks, including picrites, basalts, dacites, rhyodacites, and rhyolites, and volcanogenic–sedimentary rocks, such as tuffs and tuff breccias. In this article, oxyfluoride (La, Ce) (O_nF_m)₃ mineralization, occurring in the contact zone between the metabasalts and quartz sandstones, is described for the first time in the literature. This is represented by compounds of variable compositions forming an isomorphic series: trifluoride, (La, Ce)F₃–oxyfluoride, (La, Ce)OF–oxide, and (La, Ce)₂O₃. By analyzing several binary phase diagrams, significant coordination between oxygen, fluorine, and cerium in the chemical composition of oxyfluorides has been highlighted. However, the behavior of lanthanum has been shown to exhibit some irregularity. The genesis of oxyfluoride mineralization is attributed to the regional metamorphism of rocks within the Shatak Formation. During the hydrothermal process, the decomposition of fluorapatite, which is unstable during both hydrothermal metamorphism and supergene processes, resulted in the release of fluorine, as well as potentially lanthanum and cerium. Variations in the chemical composition of oxyfluorides, which are formed in the presence of an excess of oxygen resulting from water dissociation, are determined by local differences in the content of the main components within the forming microfractures. Full article

The Norilsk ore district is one of the world leaders in the production of platinum metals. Long-term research focused on the detection of sulfide platinum-copper-nickel ores contributed to the accumulation of a large volume of scientific material on the geology and mineralization of the Norilsk area. Despite this, the issue of the composition of the initial melt for ore-bearing intrusive complexes and its degree of enrichment with noble metals remains open. Intrusive rocks of the Norilsk region are rarely analyzed for their ratio of noble metals. However, the analysis and comparison of geochemical parameters of different types of intrusions allows us to draw important conclusions not only about the composition of the initial magmas of ore-bearing complexes, but also about the formation conditions of the intrusions. This study demonstrates the distribution of platinum metals, gold and silver in the main petrographic differentiates of the Kharaelakh, Talnakh, Vologochan intrusions and Kruglogorsk-type intrusion. The regularities and variations of the distribution of metals depend on the host rocks. There are two series of rocks in the inner structure of the ore-bearing intrusions: 1. Picritic and taxitic gabbro-dolerites enriched in PGE-Au-Ag mineralization which forms disseminated ores at intrusion bottoms (ore-bearing rocks). 2. Olivine-, olivine-bearing, olivine-free gabbro-dolerites and leucogabbro with poor sulfide mineralization at the upper part of the intrusions (ore-free rocks). There is a distinct correlation between PGE, Cu, S and to a lesser extent correlation with Ni in the first rock group, which is a characteristic of sulfide PGE-Cu-Ni deposits. In the second group, correlations are also revealed, but the correlation coefficients are lower. The main element controlling the distribution of platinum metals is copper. The taxitic gabbro-dolerites of the Talnakh intrusion are the most enriched by noble metals. According to noble metal patterns the rocks of the Kharaelakh intrusion show the highest degree of melting of the initial mantle material during the formation of parental magmas chambers. Despite some differences, the geochemical features of the studied rocks indicate the similar characteristics of the accumulation of gold, silver and platinum metals in the intrusions of the Talnakh, Kruglogorsk and Zubovsk types, which allow suggesting the close conditions for the formation of ore mineralization of these intrusions. Full article

The Tomtor massif is a polychronous ring zonal complex of alkaline ultramafic and carbonatite rocks containing unique Nb and REE deposits. Mineralogical and geochemical studies of minerals from different types of silicate rocks and carbonatites of the Tomtor massif were performed. For excluding traces of the interaction between silicate and carbonatite melts, we limited ourselves to the study of independent small secant bodies located in the immediate vicinity of the massif itself. The presence of through mineral series in various silicate igneous rocks and carbonatite ores of high-titanium chromium spinels, rare-metal, ore and other exotic phases with similar compositional trends was defined. Such studies will help reveal the mineralogical criteria for the genetic relationship between silicate melts and associated carbonatite derivatives, which can form rich rare elements mineralization. Also, such studies help to improve the petrochemical and mineralogical criteria for dividing potentially diamond-bearing magmatites (typical kimberlites) from non-diamond-bearing kimberlites, alpicrites and other non-diamond-bearing rocks convergent to kimberlites, which are formed under different physicochemical conditions. The existence of polychronous complex ore–magmatic ring complexes, such as the Tomtor massif, indicates the existence of large deep intraplate magma-generating chambers in the lithospheric mantle. Full article

Zoned plutons, composed of dunites, pyroxenites, and gabbroic rocks, have been referred to as the Ural-Alaskan type complexes (UA-complexes) and occur in numerous paleo-arc settings worldwide. Many of these complexes are source rocks for economic placers of platinum-group metals. Thus, it is important to understand how UA-complexes form and the origin and behavior of platinum-group elements (PGEs). It is widely assumed that the UA-complexes result from differentiation of supra-subduction high-Ca high-Mg sub-alkaline magmas. However, there is a lack of direct evidence for the existence and differentiation of such magmas, mainly because cases of UA-complexes being spatially and temporally linked to co-genetic volcanics are unknown. We studied an UA-complex from the Tumrok range (Eastern Kamchatka) where a dunite-clinopyroxenite-gabbro assemblage is spatially and temporary related to high-Ca volcanics (i.e., picrites and basalts). Based on the mineral and chemical composition of the rocks, mineral chemistry, and composition of melt inclusions hosted within rock-forming minerals, we conclude that the intrusive assemblage and the volcanics are co-genetic and share the same parental magma of ankaramitic composition. Furthermore, the compositions of the plutonic rocks are typical of UA-complexes worldwide. Finally, the rocks studied exhibit a full differentiation sequence from olivine-only liquidus in picrites and dunites to eutectic crystallization of diopside or hornblende, plagioclase, and K-Na feldspar in plagio-wehrlites and gabbroic rocks. All these results make the considered volcano–plutonic complex a promising case for petrological studies and modelling of UA-complex formation. Full article

The volcanic rocks in the Vologochan syncline, the Khikey River valley, and Mount Sunduk, within the Norilsk area in the NW Siberian large igneous province, have been studied. They belong to the Ivakinsky, Syverminsky, Gudchikhinsky, Khakanchansky, Nadezhdinsky, Tuklonsky, and Morongovsky Formations. These Formations consist of trachybasalts, picritic basalts and tholeiitic basalts with aphyric and porphyritic textures, and intersertal and poikiloofitic structures. For the first time, we demonstrate the variations in the structure and composition of these Formations along the strike, based on 151 analyses of the major and trace elements in the rocks. The thickness of all the Formations, excepting the Morongovsky, reduce dramatically from the Yenisey–Khatanga trough to the Tunguska syneclise, and they pinch out in the east of the Norilsk area and are attributed to riftogen (rift) basalts. The rock compositions also change in this direction, especially in the Gudchikhinsky and Nadezhdinsky Formations. The two subformations of the Gudchikhinsky formation, the lower and upper, disappear in the east, so the Gudchikhinsky consists only of high-Mg rocks, picritic basalts, and picrites. The composition of the Nadezhdinsky formation varies intensely in its (Gd/Yb)n and (Th/Nb) ratios from the Vologochan syncline to the Khikey River valley. These structural and compositional variabilities differ between the rift formations and the platform ones. Two gabbro–dolerite sills from these areas that are close to the Norilsk and Ergalakh intrusive complexes have been studied. The metal contents in volcanic and intrusive rocks are similar and do not differ from the barren rocks of the South Pyasinsky massif comprising the PGE-Cu-Ni deposits. Only the Gudchikhinsky Formation contains elevated Cu and Ni concentrations. These features and the coinciding spatial distribution of the ore-bearing intrusions and picrites of the Gudchikhinsky rocks in the Norilsk–Igarka paleorift suggest their genetic link. It is proposed that the initial sulfides could have been formed in the mantle, as the Gudchikhinsky picrites, transported to the lower crust, and then involved by the trap magmas in the origin of the ore-bodies in the Norilsk deposits. Full article

The Oktyabr’skoe deposit in the Norilsk ore district is the largest platinum-copper-nickel deposit in the world. It contains a huge main orebody (2.4 km³) of massive sulfide ores and some smaller sulfide bodies. Almost all publications on this deposit are devoted to the main orebody. However, to solve the problems of the deposit genesis, it is necessary to take into account the geological structure of the entire area and the composition of all orebodies. For the first time we present data on the inner structure, geochemical and mineralogical characteristics of the intrusive body, and related the disseminated and massive sulfide ores (orebody number C-5) in the northeastern flank of the deposit. The intrusion studied in the core of the borehole RG-2 consists of several horizons including the following rock varieties (from bottom to top): olivine gabbro-dolerites, taxitic gabbro-dolerites, picritic gabbro-dolerites, troctolites, olivine-free gabbro-dolerites, ferrogabbro, and leucogabbro. The intrusion shows a strong differentiated inner structure where high-Mg rocks (up to 25 wt.% MgO troctolites and picritic gabbro-dolerites) in the bottom are associated with low-Mg rocks (6–7 wt.%, gabbro-dolerites, leucogabbro, ferrogabbro) without intermediate differentiated members (8–12 wt.% MgO olivine gabbro-dolerites). Rocks are characterized by low TiO₂ content (≤1 wt.%). Taxitic gabbro-dolerites, picritic gabbro-dolerites, and troctolites contain disseminated sulfide chalcopyrite-pyrrhotite mineralization (32 m thick). Cu and Ni concentrations reach up 0.74 and 0.77 wt.%, respectively. Massive ores (27 m) occur in the bottom part of the intrusion. The ores consist of pentlandite, chalcopyrite and pyrrhotite, the latter mineral dominates. Their chemical composition is stable: Cu/Ni ~1, Pd/Pt varies from 5 to 6. The C-5 orebody is similar to the C-3 orebody in terms of mineral and chemical compositions, and differ from the nearby the C-4 orebody which is characterized by a Cu/Ni ratio changing from 5 to 8. On the basis of geochemical and mineralogical data, it is assumed that orebodies C-3 and C-5 are associated with one intrusion, while the orebody number C-4 is related to another intrusive body. Thus, the deposit has a more complex structure and includes several more intrusions than is usually considered. Full article

The end-Permian Emeishan Large Igneous Province (ELIP) in SW China is widely accepted to have formed by mantle plume activities, forming voluminous flood basalts and rare picrites. Although many studies were performed on the petrogenesis and tectonic setting, the detailed conditions and processes within the magma chamber(s) remain unsolved. In this study, we studied the sector-/oscillatory-zoned clinopyroxene (Cpx) phenocrysts and performed Cpx-liquid thermobarometric calculation to constrain the physicochemical processes within the magma chambers. The results show that Cpx phenocrysts from the high-Mg basalts were crystallized at 4–27 (average 17) km, whilst those from the low-Mg basalt were crystallized at 0–23 (average 9) km depth. The sector and oscillatory Cpx zoning in the high-Mg basalts show that the magma had experienced undercooling and multistage recharge events in the deep-staging chamber(s). The magma replenishments may have eventually led to the eruption of high-Mg basalts, and magma ascent to the upper crust for further fractionation to form the low-Mg basalts and mafic intrusions. Full article

The Niubiziliang Ni-(Cu) deposit is the first magmatic Ni-Cu sulfide deposit in the North Qaidam Orogenic Belt (NQOB), NW China, and plays a significant role in geological evolution, Ni-Cu mineralization, and exploration in the NQOB. Here, we report on the mineral chemistry, S-Pb-O isotopes, and S/Se ratios of the mafic-ultramafic complex, which provide insights on the parental magma, evolution, and sulfur saturation mechanism. The Niubiziliang mafic-ultramafic intrusion contains four ore blocks and about ten Ni-(Cu) ore/mineralization bodies. Olivines in Niubiziliang belong to the species of chrysolite with Fo values of 88~89, and the pyroxenes are mainly orthopyroxene (En = 79~82) and clinopyroxene (En = 44~40). The olivines and some pyroxenes likely crystallized in a magma chamber at a depth of 35.45~36.55 km at a high temperature (1289~1369 °C) and pressure (9.38~9.67 kbar), whereas the Niubiziliang complex formed at a moderate depth (8.13~8.70 km) with a temperature and pressure of 1159~1253 °C and 2.15~2.30 kbar, respectively. The parental magma was considered to be high-Mg picritic basalt with MgO and NiO contents of 14.95~16.58% and 0.053~0.068%, respectively, which indicated high-degree partial melting of the depleted mantle. The mantle-derived primary magma underwent significant fractional crystallization and crustal assimilation and contamination, which was strongly supported by S-Pb-O isotope data and S/Se ratios, resulting in sulfur saturation and sulfide immiscibility in the magma. Crustal assimilation and contamination contributed more to sulfur saturation than fractional crystallization. Full article

The purpose of this study is to show the patterns of distribution of disseminated sulfide in layered rocks based on the numerous geochemical and mineralogical data obtained for eight boreholes of the Norilsk intrusion (southern part of the Norilsk 1 deposit). There is a common trend of sulfide liquid fractionation in the Main Ore Horizon, which is composed of picritic and taxite (or olivine) gabbro-dolerites: the Ni/Cu in both rock types decreases down all sections, indicating an increase in the degree of fractionation of the sulfide liquid from top to bottom. On the contrary, the Ni/Fe ratios in pentlandite increase in this direction due to an increase in sulfur fugacity. However, picrite and taxite/olivine gabbro-dolerites are very distinctly separated by Ni/Cu values: these values are >1 in picritic gabbro-dolerite while they are always <1 in taxite/olivine gabbro-dolerite. These rock types are distinguished by sulfide assemblages. The first includes troilite, Fe-rich pentlandite, chalcopyrite, cubanite, talnahite, bornite and copper (low sulfur association); the second one is composed of monoclinic pyrrhotite, chalcopyrite, Ni-rich pentlandite and pyrite (high sulfur association). A two-stage magma injection with different ore specializations is supposed for picritic and taxite/olivine gabbro-dolerites. Full article

Field, petrological and mineral chemistry for meta-volcanic rocks from the Aravalli sequence (Aravalli Craton, India) are presented. Field evidence such as volcanic flows and suspect pillow lava structures, dominant Fe-tholeiite lava flows intercalated with quartzites and argillaceous sediments, indicate rift tectonic environment. Primary mineralogy was obliterated during post-magmatic processes such as metamorphism corresponding to the greenschist to lower amphibolite facies conditions. The rock’s mineral composition was overprinted by plagioclase–chlorite–amphibole–epidote assemblage. The relicts of clinopyroxene were observed. The P-T estimation indicates a temperature of 550–600 °C for the pressure ranging from 3.0 to 7.0 kbar for the majority of amphiboles and 8.0–10.7 kbar for the minority. Geochemically, these rocks are komatiitic (picritic) and high-Fe tholeiitic basalts with 45.06−59.2 wt.% SiO₂ and MgO content from 5 to 22.4 wt.% and Mg# of 17 to 71. They show large-ion lithophile elements (LILE) and light rare-earth elements (LREE) enrichment. Chondrite normalized rare-earth elements (REE) patterns for the Aravalli lava are moderately enriched with (La/Sm)_N = 1.1−3.85, (La/Yb)_N from 1.49 (komatiites) to 14.91 (komatiitic basalts). The trace element systematics with the negative Nb, P and Zr anomalies reflect their derivation from enriched sub-continental lithospheric sources, although minor crustal contamination cannot be ruled out. Aravalli rocks are considered to represent the transition from continental rift magmatism to shallow submarine eruption. Full article

Olivine forsterite contents [Fo = 100 × Mg/(Mg + Fe) in mol%] and minor–trace element concentrations can aid our understanding of the Earth’s mantle. Traditionally, these data are obtained by electron probe microanalysis for Fo contents and minor elements, and then by laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) for trace elements. In this study, we demonstrate that LA–ICP–MS, with a simplified 100% quantification approach, allows the calculation of Fo contents simultaneously with minor–trace elements. The approach proceeds as follows: (1) calculation of Fo contents from measured Fe/Mg ratios; (2) according to the olivine stoichiometric formula [(Mg, Fe)₂SiO₄] and known Fo contents, contents of Mg, Fe and Si can be computed, which are used as internal standards for minor–trace element quantification. The Fo content of the MongOLSh 11-2 olivine reference material is 89.55 ± 0.15 (2 s; N = 120), which agrees with the recommended values of 89.53 ± 0.05 (2 s). For minor–trace elements, the results matched well with the recommended values, apart from P and Zn data. This technique was applied to olivine phenocrysts in the Lijiang picrites from the Emeishan large igneous province. The olivine compositions suggest that the Lijiang picrites have a peridotitic mantle source. Full article