Genesis and magmatic-hydrothermal evolution of the Shapoling Mo deposit, East Qinling, China: Insights from geochronology, petrogenesis and fluid evolution
Genesis and magmatic-hydrothermal evolution of the Shapoling Mo deposit, East Qinling, China: Insights from geochronology, petrogenesis and fluid evolution
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中国东秦岭沙坡岭钼矿床的成因和岩浆热液演化：地质年代学、岩石成因和流体演化的见解
DOI：
10.1016/j.oregeorev.2022.104789
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发表时间：
2022
影响因子：
3.3
通讯作者：
J.Y.
中科院分区：
文献类型：
--
作者：
Hu;X.K.;Zhang;S.T.;Tsunogae;T.;Tang;L.;Li;W.J.;Sheng;Y.M.;Feng;J.Y.
沙坡岭存款矿床位于东秦岭熊耳山地区，以岩浆-热液钼脉系统为特征。本文报道了砂岭存款矿床的全岩地球化学、锆石U-Pb-Hf-O同位素、石英H-O同位素和流体包裹体等资料。利用这些数据，我们研究了与钼矿化有关的花岗岩类的岩石成因和形成钼存款的岩浆-热液演化过程。砂坪存款中的花岗岩类为偏铝质、碱性-钙碱性、钾玄质-高钾系列，属高度分馏的I型花岗岩类。这些花岗岩强烈富集轻稀土和大离子亲石元素，亏损重稀土，铕负异常和高场强元素，主要分布在太华群岩石范围内。沙坡岭花岗岩类的Sr/Y和（La/Yb）N值大多低于典型埃达克质岩石，表明其母岩浆形成于较低的压力下。因此，沙坡岭花岗岩类是在地壳较薄的水平上，由挤压向拉张的构造转换过程中岩石圈减薄而形成的。沙坡岭花岗岩的锆石U-Pb年龄为132.9 ± 1.3 ~ 126.5 ± 0.7Ma。εHf（t）值和δ 18 O锆石值分别为-19.1 ~-8.0和5.33‰ ~ 6.30‰，与部分熔融的太华群与幔源组分混合的Hf-O同位素特征一致。流体包裹体显微测温结果表明，砂坪钼存款形成的热液流体由早期的H2O-NaCl-CO2体系中的中低盐度富CO2流体，转变为晚期的H2O-NaCl低盐度流体。石英的δD值为−93.3‰ ~ −78.2‰，δ 18 O值为−5.14‰ ~ 0.92‰，表明岩浆源区占主导地位，但后期被大气降水稀释。流体沸腾是控制镁铝榴石析出的关键因素。研究结果揭示了钼系的形成与岩浆系统的长期活跃、热软流圈的上涌和强烈的幔壳相互作用有关。岩浆房中的幔源物质不断补充延长的岩浆系统，为热液系统提供物质，控制了沙坪钼存款的形成。
The Shapoling deposit, located in Xiong'ershan area, East Qinling, China, is characterized by a magmatic-hydrothermal Mo vein system. We present whole-rock geochemical, zircon U-Pb-Hf-O isotopic, quartz H-O isotopic and fluid inclusion data for the Shapoling deposit. We use these data to investigate the petrogenesis of granitoids associated with Mo mineralization and the processes of magmatic-hydrothermal evolution that formed the Mo deposit. The granitoids from the Shapoling deposit are metaluminous, alkalic to calc-alkalic, shoshonitic to high-K series, and belong to highly fractionated I-type granitoids. These granitoids are strongly enriched in light rare earths (LREEs) and large ion lithophile elements (LILE), but depleted in heavy rare earths (HREEs) with negative europium anomalies and high field-strength elements (HFSE), mostly plotting in the range of the Taihua Group rocks. Most of the Shapoling granitoids show relatively lower Sr/Y and (La/Yb)Nthan the typical adakitic rocks, showing that the parental magmas were generated under lower pressure. Therefore, the Shapoling granitoids were generated at thin crustal levels by lithospheric thinning process linked to the tectonic transition from compression to extension. Zircon U-Pb ages of the Shapoling granitoids range from 132.9 ± 1.3 Ma to 126.5 ± 0.7 Ma. The εHf(t)values and δ18Ozirconvalues show a variation trend from −19.1 to −8.0 and 5.33‰ to 6.30‰, which are consistent with Hf-O isotopic features of mixing of the partially melted Taihua Group with mantle-derived components. FIluid inclusion microthermometry results suggest that the hydrothermal fluids forming the Shapoling Mo deposit changed from early moderate- to low-salinity CO2-rich fluids in the H2O-NaCl-CO2system, to late H2O-NaCl low-salinity fluids. The corresponding quartzs have δD values varying from −93.3‰ to −78.2‰ and δ18O values from −5.14‰ to 0.92‰, indicating a dominant magmatic source but were diluted by meteoric water in the late stage. Fluid boiling is the key factor that controlling the precipitation of molybdenite. Our study provides insights into the formation of Mo system associated with a prolonged and active magmatic system, upwelling of hot asthenosphere and intense mantle-crust interaction. The prolonged magmatic system is steadily replenished by mantle-derived materials in the magma chamber, which feed the hydrothermal systems and govern the formation of the Shapoling Mo deposit.