藏北羌塘中部果干加年山斜长花岗岩定年及其构造意义  

Dating and tectonic significance of plagiogranite from Guoganjianian Mountain,central Qiangtang, northern Tibet, China

作　　者：施建荣[1] 董永胜[1] 王生云[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《地质通报》2009年第9期1236-1243,共8页Geological Bulletin of China

基　　金：国家自然科学基金项目(编号:40872146;40672147);中国地质调查局项目(编号:1212010818115)资助

摘　　要：果干加年山蛇绿岩中首次发现了斜长花岗岩,它对于蛇绿岩的成因研究,特别是对蛇绿岩形成和演化过程的精确年龄测定,具有重要意义。通过野外地质特征和岩石学、地球化学、同位素年代学初步研究,斜长花岗岩具有埃达克岩的特点,如高Al(14.84%～15.35%)、Sr(338×10-6～356×10-6)、Sr/Y值(46.94～55.45)和贫Y、Yb(Y=6.42×10-6～7.20×10-6,Yb=0.56×10-6～0.63×10-6)等。斜长花岗岩锆石SHRIMP U-Pb年龄为348Ma±9Ma,代表了洋壳俯冲的时间。上述地球化学特征表明,果干加年山斜长花岗岩可能是俯冲洋壳高压条件下直接部分熔融形成的,产于消减带之上的环境(SSZ型)。Plagiogranite is firstly found in the ophiolite in Guoganjianian Mountain. It has great significance for the petrogenesis of ophiolite studies,especially for the precise dating of ophiolite formation and evolution. Based on the study of field geological charac- teristics, petrology,geochemistry and isotope geochronology, the authors suggest the plagiogranite has similar characteristics of adakite, which is high in Al2O3（14.84%～15.35%）,Sr（338×10-6～356×10-6）,Sr/Y（Sr/Y=46.94～55.45）and low in Y,Yb（Y=6.42×10-6～7.20× 10-6,Yb=0.56×10-6～0.63×10-6）. Zircon SHRIMP U-Pb dating age is （348±9） Ma and it represents the subduction time of oceanic crust. The above geochemical characteristics indicate that plagiogranite in the Guoganjianian Mountain is the product of direct partial melting of subduction plate in high pressure,and these granites are likely produced in the environment of subduction zone（SSZ type）.

关 键 词：青藏高原 羌塘地区 果干加年山蛇绿岩 斜长花岗岩 锆石SHRIMP U-PB定年 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]