Cretaceous magmatism and metallogeny in the Bangong–Nujiang metallogenic belt, central Tibet: Evidence from petrogeochemistry, zircon U–Pb ages, and Hf–O isotopic compositions

2017 ◽  
Vol 41 ◽  
pp. 110-127 ◽  
Author(s):  
Guang-Ming Li ◽  
Ke-Zhang Qin ◽  
Jin-Xiang Li ◽  
Noreen J. Evans ◽  
Jun-Xing Zhao ◽  
...  
Keyword(s):  
Isotopic Compositions ◽  
Metallogenic Belt ◽  
Cretaceous Magmatism ◽  
Central Tibet

scholarly journals Ore Genesis of the Chuduoqu Pb-Zn-Cu Deposit in the Tuotuohe Area, Central Tibet: Evidence from Fluid Inclusions and C–H–O–S–Pb Isotopes Systematics

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 285 ◽  
Author(s):  
Yong-Gang Sun ◽  
Bi-Le Li ◽  
Feng-Yue Sun ◽  
Ye Qian ◽  
Run-Tao Yu ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Stage Iv ◽  
Isotopic Compositions ◽  
Ore Bodies ◽  
Metallogenic Belt ◽  
Ore Minerals ◽  
Ore Mineralization ◽  
Deposit Type ◽  
Homogenization Temperatures ◽  
Central Tibet

The Chuduoqu Pb-Zn-Cu deposit is located in the Tuotuohe area in the northern part of the Sanjiang Metallogenic Belt, central Tibet. The Pb-Zn-Cu ore bodies in this deposit are hosted mainly by Middle Jurassic Xiali Formation limestone and sandstone, and are structurally controlled by a series of NWW trending faults. In this paper, we present the results of fluid inclusions and isotope (C, H, O, S, and Pb) investigations of the Chuduoqu deposit. Four stages of hydrothermal ore mineralization are identified: quartz–specularite (stage I), quartz–barite–chalcopyrite (stage II), quartz–polymetallic sulfide (stage III), and quartz–carbonate (stage IV). Two types of fluid inclusions are identified in the Chuduoqu Pb-Zn-Cu deposit: liquid-rich and vapor-rich. The homogenization temperatures of fluid inclusions for stages I–IV are 318–370 °C, 250–308 °C, 230–294 °C, and 144–233 °C, respectively. Fluid salinities range from 2.07 wt. % to 11.81 wt. % NaCl equivalent. The microthermometric data indicate that the fluid mixing and cooling are two important mechanisms for ore precipitation. The H and O isotopic compositions of quartz indicate a primarily magmatic origin for the ore-forming fluids, with the proportion of meteoric water increasing over time. The C and O isotopic compositions of carbonate samples indicate that a large amount of magmatic water was still involved in the final stage of mineralization. The S and Pb isotopic compositions of sulfides, demonstrate that the ore minerals have a magmatic source. On a regional basis, the most likely source of the metallogenic material was regional potassium-enriched magmatic hydrothermal fluid. Specifically for the Chuduoqu Pb-Zn-Cu deposit, the magmatic activity of a syenite porphyry was the likely heat source, and this porphyry also provided the main metallogenic material for the deposit. Mineralization took place between 40 and 24 Ma. The Chuduoqu deposit is a mesothermal hydrothermal vein deposit and was formed in an extensional environment related to the late stage of intracontinental orogenesis resulting from India–Asia collision. The determination of the deposit type and genesis of Chuduoqu is important because it will inform and guide further exploration for hydrothermal-type Pb and Zn deposits in the Tuotuohe area and in the wider Sanjiang Metallogenic Belt.

Isotopic analyses of clinopyroxene in mantle xenoliths demonstrate the effects of kimberlite melt metasomatism upon the lithospheric mantle

2020 ◽  
Author(s):  
Angus Fitzpayne ◽  
Andrea Giuliani ◽  
Janet Hergt ◽  
Jon Woodhead ◽  
Roland Maas
Keyword(s):  
Trace Element ◽  
Lithospheric Mantle ◽  
Mantle Metasomatism ◽  
Mantle Xenoliths ◽  
Isotopic Compositions ◽  
Isotopic Analyses ◽  
Cretaceous Magmatism

<p>As clinopyroxene is the main host of most lithophile elements in the lithospheric mantle, the trace element and radiogenic isotope systematics of this mineral have frequently been used to characterise mantle metasomatic processes. To further our understanding of mantle metasomatism, both solution-mode Sr-Nd-Hf-Pb and in situ trace element and Sr isotopic data have been acquired for clinopyroxene grains from a suite of peridotite (lherzolites and wehrlites), MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside), and PIC (Phlogopite-Ilmenite-Clinopyroxene) rocks from the Kimberley kimberlites (South Africa). The studied mantle samples can be divided into two groups on the basis of their clinopyroxene trace element compositions, and this subdivision is reinforced by their isotopic ratios. Type 1 clinopyroxene, which comprises PIC, wehrlite, and some sheared lherzolite samples, is characterised by low Sr (~100–200 ppm) and LREE concentrations, moderate HFSE contents (e.g., ~40–75 ppm Zr; La/Zr < 0.04), and restricted isotopic compositions (e.g., <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> = 0.70369–0.70383; εNd<sub>i</sub> = +3.1 to +3.6) resembling those of their host kimberlite magmas. Available trace element partition coefficients can be used to show that Type 1 clinopyroxenes are close to equilibrium with kimberlite melt compositions, supporting a genetic link between kimberlites and these metasomatised lithologies. Thermobarometric estimates for Type 1 samples indicate equilibration depths of 135–155 km within the lithosphere, thus showing that kimberlite melt metasomatism is prevalent in the deeper part of the lithosphere beneath Kimberley. In contrast, Type 2 clinopyroxenes occur in MARID rocks and coarse granular lherzolites, which derive from shallower depths (<130 km), and have higher Sr (~350–1000 ppm) and LREE contents, corresponding to higher La/Zr of >~0.05. The isotopic compositions of Type 2 clinopyroxenes are more variable and extend from compositions resembling the “enriched mantle” towards those of Type 1 rocks (e.g., εNd<sub>i</sub> = -12.7 to -4.4). To constrain the source of these variations, in situ Sr isotope analyses of clinopyroxene were undertaken, including zoned grains in Type 2 samples. MARID and lherzolite clinopyroxene cores display generally radiogenic but variable <sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> values (0.70526–0.71177), which might be explained by the interaction between peridotite and melts from different enriched sources with the lithospheric mantle. In contrast, the rims of these Type 2 clinopyroxenes trend towards compositions similar to those of the host kimberlite and Type 1 clinopyroxene from PIC and wehrlites. These results are interpreted to represent clinopyroxene overgrowth during late-stage (shortly before/during entrainment) metasomatism by kimberlite magmas. Our study shows that an early, pervasive, alkaline metasomatic event caused MARID and lherzolite genesis in the lithospheric mantle beneath the Kimberley area, which was followed by kimberlite metasomatism during Cretaceous magmatism. This latter event is the time at which discrete PIC, wehrlite, and sheared lherzolite lithologies were formed, and MARID and granular lherzolites were partly modified.</p>

Simultaneous growth and reworking of the Lhasa basement: A case study from Early Cretaceous magmatism in the north-central Tibet

Lithos ◽  
2020 ◽  
pp. 105863
Author(s):  
Wei Wang ◽  
Qing-guo Zhai ◽  
Pei-yuan Hu ◽  
Sun-lin Chung ◽  
Yue Tang ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
North Central ◽  
The North ◽  
Cretaceous Magmatism ◽  
Central Tibet ◽  
Simultaneous Growth

scholarly journals Tectonic Control, Reconstruction and Preservation of the Tiegelongnan Porphyry and Epithermal Overprinting Cu (Au) Deposit, Central Tibet, China

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 398 ◽  
Author(s):  
Yang Song ◽  
Chao Yang ◽  
Shaogang Wei ◽  
Huanhuan Yang ◽  
Xiang Fang ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Isotopic Signature ◽  
Epithermal Deposit ◽  
Porphyry Deposit ◽  
Tectonic Control ◽  
Quartz Veins ◽  
High Sulfidation ◽  
Metallogenic Belt ◽  
Alteration Minerals ◽  
Central Tibet

The newly discovered Tiegelongnan Cu (Au) deposit is a giant porphyry deposit overprinted by a high-sulfidation epithermal deposit in the western part of the Bangong–Nujiang metallogenic belt, Duolong district, central Tibet. It is mainly controlled by the tectonic movement of the Bangong–Nujiang Oceanic Plate (post-subduction extension). After the closure of the Bangong–Nujiang Ocean, porphyry intrusions emplaced at around 121 Ma in the Tiegelongnan area, which might be the result of continental crust thickening and the collision of Qiangtang and Lhasa terranes, based on the crustal radiogenic isotopic signature. Epithermal overprinting on porphyry alteration and mineralization is characterized by veins and fracture filling, and replacement textures between two episodes of alteration and sulfide minerals. Alunite and kaolinite replaced sericite, accompanied with covellite, digenite, enargite, and tennantite replacing chalcopyrite and bornite. This may result from extension after the Qiangtang–Lhasa collision from 116 to 112 Ma, according to the reopened quartz veins filled with later epithermal alteration minerals and sulfides. The Tiegelongnan deposit was preserved by the volcanism at ~110 Ma with volcanic rocks covering on the top before the orebody being fully weathered and eroded. The Tiegelongnan deposit was then probably partly dislocated to further west and deeper level by later structures. The widespread post-mineral volcanic rocks may conceal and preserve some unexposed deposits in this area. Thus, there is a great potential to explore porphyry and epithermal deposit in the Duolong district, and also in the entire Bangong–Nujiang metallogenic belt.

Geochronology, geochemistry, and zircon Hf isotopic compositions of Mesozoic intermediate–felsic intrusions in central Tibet: Petrogenetic and tectonic implications

Lithos ◽  
2014 ◽  
Vol 198-199 ◽  
pp. 77-91 ◽  
Author(s):  
Jin-Xiang Li ◽  
Ke-Zhang Qin ◽  
Guang-Ming Li ◽  
Jeremy P. Richards ◽  
Jun-Xing Zhao ◽  
...  
Keyword(s):  
Isotopic Compositions ◽  
Tectonic Implications ◽  
Central Tibet
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