PGE and Isotope (Hf-Sr-Nd-Pb) Constraints on the Origin of the Huangshandong Magmatic Ni-Cu Sulfide Deposit in the Central Asian Orogenic Belt, Northwestern China

2013 ◽  
Vol 108 (8) ◽  
pp. 1849-1864 ◽  
Author(s):  
T. Sun ◽  
Z.-Z. Qian ◽  
Y.-F. Deng ◽  
C. Li ◽  
X.-Y. Song ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Northwestern China ◽  
Sulfide Deposit ◽  
Central Asian

Late Cenozoic Coal Fires in the Liuhuanggou Area (Xinjiang, Northwestern China): Ages, Controlling Factors and Evolution

2021 ◽  
Author(s):  
B. Chen ◽  
M. Franceschi ◽  
Y. Wang ◽  
X. Duan ◽  
X. Jin ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Northwestern China ◽  
Metamorphic Rocks ◽  
Coal Seams ◽  
Erosion And Deposition ◽  
Fluvial Terraces ◽  
Coal Fire ◽  
Central Asian ◽  
Coal Fires

Abstract —Coal fires are a phenomenon that can be observed worldwide in areas where rocks containing coal seams are exposed and can pose major environmental threats. A coal fire can begin through spontaneous combustion when coals are exposed to dry and oxygen-rich near-surface conditions. Burning, depending on the temperature of heating, causes baking or even melting of the surrounding rocks and the formation of different types of combustion metamorphic rocks. In Northwestern China, coal fire occurrences are concentrated at the edges of the sedimentary basins or at the margins of orogenic belts, where coalrich units were exposed owing to the Indo-Eurasian collision. On the northern margin of the Tianshan range, evidence of coal fires is widespread in the Jurassic sedimentary units containing coal seams which outcrop along the Central Asian Orogenic Belt. In some cases, coal fires are active and can be linked to ongoing mining activity, but outcrops of combustion metamorphic rocks not associated with fires are also found and are indicative of past burning events. We examine combustion metamorphic rocks outcropping in the Toutunhe River valley (Liuhuangou area, Xinjiang, Northwestern China). Combustion metamorphic rocks in the study area were mapped and classified according to their morphological and mineralogical characteristics. Outcrops are exposed at various heights on the valley flanks, which are characterized by the presence of multiple levels of fluvial terraces. These terraces are indicative of the phases of erosion and deposition of the Toutunhe River and testify to tectonic uplift. The investigation of the stratigraphic and crosscutting relationship of combustion metamorphic rocks with terrace deposits and apatite fissiontrack dating made it possible to determine that at least four phases of coal fire activity occurred from late Miocene to Quaternary. The first and oldest burning phase dates back to 10 ± 1.3 Ma and terminated prior to 2–3 Ma; the second was active before ~550 ka; the third had terminated by ~140 ka; the fourth began later than ~5.7 ka. The relationships between combustion metamorphic rocks and fluvial terraces further suggest that coal fire ignition/extinction in the area since the Miocene have been linked to the interplay between the uplift of the Central Asian Orogenic Belt and the phases of fluvial erosion and deposition in interglacial periods.

Genesis of the Wuxing Pt–Pd-rich Cu–Ni sulfide deposit in the eastern Central Asian Orogenic Belt: evidences from geochronology, elemental geochemistry, and Sr–Nd–Hf isotopic data

2019 ◽  
Vol 56 (4) ◽  
pp. 380-398 ◽  
Author(s):  
Jing-gui Sun ◽  
Yun-peng He ◽  
Ji-long Han ◽  
Zhong-yu Wang
Keyword(s):  
Crustal Contamination ◽  
Early Period ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Geochemical Data ◽  
Sulfide Deposit ◽  
Late Period ◽  
Enriched Mantle ◽  
Central Asian ◽  
T Values

The Wuxing Pt–Pd-rich Cu–Ni sulfide deposit in Heilongjiang Province, Northeast China, is located to the northeast of the Dunhua–Mishan fracture of the eastern Central Asian Orogenic Belt. The mafic–ultramafic complex consist of early-period hornblende–olivine pyroxenite, diopsidite, and hornblende pyroxenite and late-period gabbro and diabase units. An early-period hornblende pyroxenite yielded a zircon U–Pb age of 208.2 ± 2.6 Ma and a late-period diabase yielded a U–Pb age of 205.6 ± 1.1 Ma, with zircon εHf(t) values of +1.24 to +8.13. The early- and late-period lithofacies are relatively enriched in LILE (Rb, Ba, and Sr) and LREE, and variably depleted in HFSE (Nb, Ta). The whole-rock and single-mineral analyses of the early-period lithofacies yield (87Sr/86Sr)i ratios of 0.7055–0.7083 and εNd(t) ratios of −7.98–+3.10. These geochemical data suggest that the parental magmas of the Wuxing complex are high-Mg subalkaline basaltic in nature and were derived from an enriched mantle source. The magmas chamber formed after the injection of magma into the crust along with crustal contamination, producing early crystalline minerals and ore-bearing magmas. The rupturing of the magma chamber released evolved magmas, which then ascended and generated Pt–Pd-bearing lithofacies and Cu–Ni sulfide orebodies by fractional crystallization, accumulation, and liquation. During the late period, the residual magma invaded the early lithofacies and Cu–Ni orebodies. The fluids exsolved from the gabbroic magmas concentrated the mineralized metal elements and enhanced the precipitation of Pt–Pd-bearing veinlet-disseminated orebodies and Pt–Pd–Cu–Ni orebodies.

scholarly journals Dunhuang Tectonic Belt in northwestern China as a part of the Central Asian Orogenic Belt: Structural and U-Pb geochronological evidence

2018 ◽  
Vol 747-748 ◽  
pp. 281-297 ◽  
Author(s):  
Lamei Feng ◽  
Shoufa Lin ◽  
Donald W. Davis ◽  
Cees R. van Staal ◽  
Chuanzhong Song ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Northwestern China ◽  
Central Asian ◽  
Tectonic Belt ◽  
Geochronological Evidence

scholarly journals 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 ◽  
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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