川西新元古代花岗质杂岩体的锆石SHRIMP U-Pb年龄、元素和Nd-Sr同位素地球化学研究:岩石成因与构造意义

扬子块体西缘新元古代岩浆活动十分强烈,其成因对于研究Rodinia超大陆的演化有重要意义.目前对这些岩浆的成因和形成的构造背景存在地幔柱和岛弧两种不同的观点.本文对川西康滇裂谷中四川西昌一带出露的摩挲营花岗岩体和性质相似的周边花岗质小岩体,以及岩体中出露的基性岩墙进行了SHRIMP锆石U-Pb年龄、元素和Sr-Nd同位素的研究表明这些酸性、基性岩体形成于842～790Ma,基本为同时代的侵入岩;花岗岩基中普遍发育中性包体,为岩浆混合作用的表现;花岗岩起源于古老的下地壳,基性岩起源于亏损的软流圈地幔.本文的研究结果支持华南位于澳大利亚和Laurentia大陆之间的Rodinia超大陆重建模式.

SHRIMP U-Pb zircon ages and major element, trace element and Nd-Sr isotope geochemical studies of a Neoproterozoic granitic complex in western Sichuan:Petrogenesis and tectonic significance

Neoproterozoic magmatism was very intense at the western margin of the Yangtze block.The origin of the magmas has great significance for the study of the evolution of the supercontinent Rodinia.At present,there are two divergent views as to the interpretation of the origin and tectonic setting of the magmas:the mantle plume origin and island arc origin.The authors performed SHRIMP U-Pb zircon dating and major element and trace element and Sr-Nd isotope studies of the Mosuoying granitic complex and its surrounding small granitic intrusions as well as basic dikes in these intrusions exposed in the Xichang area,Sichuan,in the Sichuan-Xikang-Yunnan rift. These studies indicate that:(1)these acid and basic rock bodies all formed at 842 ~ 790 Ma and are in the main contemporaneous intrusions;(2)intermediate enclaves are pervasive in the granite batholith is the manifestation of magma mingling;and(3)granite was derived from the older lower crust,while basic rocks were derived from the depleted asthenospheric mantle.This study supports the view that South China was located in the supercontinent Redinia between the continents Australia and Laurentia in the Neoproterozoic.