Mineral Chemistry, S-Pb-O Isotopes, and S/Se Ratios of the Niubiziliang Ni-(Cu) Sulfide Deposit in North Qaidam Orogenic Belt, NW China: Constraints on the Parental Magma Composition, Evolution, and Sulfur Saturation Mechanism

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.

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Origin and Nature of Parental Magma and Sulfide Segregation of the Baixintan Magmatic Ni–Cu Sulfide Deposit, Southern Central Asian Orogenic Belt (CAOB), NW China: Insights from Mineral Chemistry of Chromite and Silicate Minerals

Minerals ◽

10.3390/min10121050 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1050

Author(s):

Banxiao Ruan ◽

Mingyang Liao ◽

Bingke Sun ◽

Chao Chen

Keyword(s):

Parental Magma ◽

Mineral Chemistry ◽

Orogenic Belt ◽

Central Asian Orogenic Belt ◽

Sulfide Deposit ◽

Type I ◽

Silicate Minerals ◽

Central Asian ◽

Southern Central ◽

Sulfide Segregation

The mineral chemistry of chromite and silicate minerals in the Baixintan magmatic Ni-Cu sulfide deposit in the Northern Tianshan, southern Central Asian Orogenic Belt (CAOB) are reported here. Two types of chromite were identified in mafic-ultramafic rocks. Type I chromite occurs as inclusions encased in olivine and has a primary and magmatic origin and homogeneous composition with Cr# values (49–66). It is characterized by high Ti contents (0.33–1.52 wt%) and small quantities of ZnO (0–0.21 wt%), MnO (0.28–0.45 wt%), and NiO (0.06–0.24 wt%) contents. In contrast, type II chromite with interstitial phase and larger compositional variations has significantly higher TiO2 (up to 6.2 wt%) and FeOt contents (up to 69.3 wt%) and slightly lower Al2O3 (minimum 3.0 wt%) and MgO contents (minimum 0.53 wt%). It is considered to crystallize from a more evolved and fractionated melt and suffers from post-magmatic alteration, such as serpentinization and chloritization. The olivine has forsterite values (Fo) varying from 76.8 to 85.6. The parental magma is characterized by high temperature (1389 °C), high pressure (3.8 Gpa), and high Mg content (11.4 wt%) with oxidized (FMQ + 1.6) and hydrous nature based on compositions of primary chromite and olivine–chromite pairs. The intrusion originated from high-degree partial melting of depleted mantle that had been modified by crustal components and metasomatized by subduction fluid in a post-orogenic extensional setting. Two stages of sulfide segregation have been recognized. Early segregation led to the depletion of platinum group elements (PGE), and disseminated sulfide mineralization was the product of later segregation. The assimilation of crustal Si and S components played more important roles on sulfide segregation rather than fractional crystallization.

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The parental magma composition, crustal contamination process, and metallogenesis of the Shitoukengde Ni‐Cu sulfide deposit in the Eastern Kunlun Orogenic Belt, NW China

Resource Geology ◽

10.1111/rge.12267 ◽

2021 ◽

Author(s):

Liang Li ◽

Dexin Zhang ◽

Shucheng Tan ◽

Fengyue Sun ◽

Chao Wang ◽

...

Keyword(s):

Crustal Contamination ◽

Parental Magma ◽

Orogenic Belt ◽

Sulfide Deposit ◽

Nw China ◽

Magma Composition

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Geochronology, geochemistry, and Sr–Nd–Hf isotopic compositions of mafic–ultramafic intrusions in the Niubiziliang Ni–(Cu) sulfide deposit, North Qaidam Orogenic Belt, NW China: Implications for magmatic source, geodynamic setting, and petrogenesis

Lithos ◽

10.1016/j.lithos.2018.12.027 ◽

2019 ◽

Vol 326-327 ◽

pp. 158-173 ◽

Cited By ~ 1

Author(s):

Lu Yu ◽

Fengyue Sun ◽

Liang Li ◽

Bile Li ◽

Bo Peng ◽

...

Keyword(s):

Orogenic Belt ◽

Geodynamic Setting ◽

Sulfide Deposit ◽

Nw China ◽

Magmatic Source ◽

Isotopic Compositions ◽

North Qaidam

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Petrology, mineral chemistry, and geochemistry of Late Triassic Ni–Cu ore-bearing mafic–ultramafic intrusions, Hongqiling, northeastern China: petrogenesis and tectonic implications

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2018-0014 ◽

2019 ◽

Vol 56 (2) ◽

pp. 111-128

Author(s):

Ai Li ◽

Jian Wang ◽

Yue Song

Keyword(s):

Crustal Contamination ◽

Parental Magma ◽

Mineral Chemistry ◽

Late Triassic ◽

Sulfide Deposit ◽

Chemical Compositions ◽

Tholeiitic Magma ◽

Average Value ◽

Central Asian ◽

History Of

The Hongqiling magmatic Ni–Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic–ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low TiO2 (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg# (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic–ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic–ultramafic intrusions and the calculated “trapped liquids” for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic–ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic–ultramafic intrusions formed in a post-collisional extensional environment.

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