地质学报2017，Vol.91Issue(4)：822-835,14.
西藏冈底斯确角弄岩体年代学、地球化学及成矿意义
Geochronology and Geochemistry of the Quejiaonong Pluton in Middle Section of Gangdese, Tibet and its Mineralization Significance
摘要
Abstract
Magmatic activities were very active in the middle section of the Gangdise during Mesozoic to Cenozoic periods,but petrogenesis and magma source of this area is still in dispute.The Early Cretaceous magmatism is not only key element for understanding magmatism-related mineralization temporally concentrated in the Gangdise,but also a window for probing geodynamic process.With the Early Cretaceous granite complex in the Quejiaonong area as an example,we conducted an integrated study of petrology,zircon U-Pb age,and elemental geochemistry and Sr-Nd isotopes.Lithological assemblages of granitoid rock are dominated by biotite granodiorite with minor quartz monzonite and rare K-feldspar granite,and belong to high-K calc-alkaline and Ⅰ type granitoids.Zircon U-Pb dating indicates that the biotite granodiorite rocks were emplaced at 127 ± 1.6Ma and are characterized by high (87 Sr/86 Sri) ratio (0.70926-0.71424),negative whole-rock εNd(t) value (-7.0～-9.1),enrichment in large ion lithophile elements and depletion in high field strength elements,displaying an affinity of volcanic arc granite.The magma was sourced from antexis of ancient lower crust materials and minor mixed mantle-derived melts,experienced significant fractional crystallization.Lithogenesis of the pluton was likely related to the slab break-off during southward subduction of Bangong-Nujiang Tethys oceanic crust during the Early Cretaceous.The Quejiaonong pluton was a continuation of eruption event of strip magma in the middle Gangdese in Early Cretaceous,resulting in strong alteration between the pluton and country rocks.High geophycial anomalous values indicate iron and tungsten mineralization with locally mineralized prospects of magnetite.Ore-forming plutons have high Ce4+/Ce3+ ratios (450-769) and temperature calculated by Ti-in-zircon thermometeris was ca.776℃,indicating that the ore-bearing magma was characterized by a relatively high oxygen fugacity and high diagenetic temperature.Spatial distribution of geochemical trend residual anomalies is controlled by geochemical anomalies is controlled by strata,fault structure and magmatic rocks,suggesting a promising outlook for iron and tungsten exploration in this area.关键词
冈底斯/早白垩世岩浆作用/岩石成因/地球化学/成矿意义Key words
Gangdese/Early Cretaceous magmatism/Petrogensis/geochemistry/Mineralization significance引用本文复制引用
王力圆,高顺宝,郑有业,李伟良,毛荣威,黄亮亮..西藏冈底斯确角弄岩体年代学、地球化学及成矿意义[J].地质学报,2017,91(4):822-835,14.基金项目
本文为中国地质调查局地质调查项目(1212011121250)和福州大学科研启动基金项目(510195)联合资助的成果. （1212011121250）
