Petrology and SHRIMP chronology of mylonitized Tianger granite,Xinjiang:Also about the dating on hydrothermal zircon rim in granite.
Petrology and SHRIMP chronology of mylonitized Tianger granite,Xinjiang:Also about the dating on hydrothermal zircon rim in granite.
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作者：
Zhu Yong
产于中天山天儿山（冰大坂）一带的片麻岩花岗岩，是早志留世花岗岩糜棱岩化过程中形成的。nww向的天儿剪切带穿过天儿花岗岩。这种所谓的片麻岩花岗岩被认为是伊利-中天山地体前寒武纪基底的组成部分。本文介绍了五谷路天儿剪切带的地质剖面，糜棱岩化花岗岩的岩石学特征及其锆石SHRIMP年代学资料。糜棱化花岗岩中的锆石具有复杂的核-幔-缘结构。锆石的表观SHRIMP年龄为470~1788Ma。锆石地幔岩浆分带明显，SHRIMP年龄在432~453 Ma之间。具有暗阴极发光图像（非发光）的热液锆石边缘形成于岩浆锆石幔幔的岩浆替换过程中，根据SHRIMP测年结果，岩浆锆石幔幔在晚期可能小于421Ma。根据锆石地幔SHRIMP数据，天儿花岗岩可能在441.6±3.8Ma（MSWD=1.06）侵入。热液锆石边缘定年为408.6±1.7Ma。热液锆石边缘的形成可能与所研究的早志留世花岗岩糜棱岩化作用有关。
The gneissic granite occurring along the Tianger mountain(Bingdaban)of the Central Tianshan Mountains was formed during the mylonitization process of the Early Silurian granite.The NWW-trending Tianger shear zone cut through the Tianger granite. This so-called gneissic granite was believed to be a component of the Precambrian basement of the Yili-Central Tianshan terrane.Here we present a geological section through the Tianger shear zone along Wuku road,petrography of the mylonitized granite and its zircon SHRIMP geochronology data.Zircons in the mylonitized granite show complex core-mantle-rim texture.The zircon cores have apparent SHRIMP ages of 470～1788Ma.The zircon mantles with clear magmatic zonation show apparent SHRIMP ages of 432～453 Ma.The hydrothermal zircon rims with dark cathodoluminescence images(non-luminescent)were formed during the mylonitization by fluid replacement of the magmatic zircon mantles at a late period probably＜421Ma based on SHRIMP dating results.The Tianger granite probably intruded during 441.6±3.8Ma(MSWD=1.06)based on the SHRIMP data on the zircon mantles.The hydrothermal zircon rim was dated at 408.6±1.7Ma.The formation of the hydrothermal zircon rim probably was related with the mylonitizing process in the studied Early Silurian granite.