宿松变质杂岩中石榴石-蓝晶石-硬绿泥石片岩形成条件及时限研究  

Investigation of P-T conditions and geochoronology for garnet-kyanite-chloritoid schist from the Susong Complex

作　　者：石永红[1] 王娟[1] 聂峰[1] 曹晟[1] 康涛[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《岩石学报》2016年第2期493-504,共12页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41272073)资助

摘　　要：宿松变质杂岩因变质程度较低,岩性较为繁杂,故其变质演化及年龄一直缺乏系统性和全面性研究,这很大程度上影响了人们对大别造山带结构框架和演化的深入理解。本次研究主要针对太湖-马庙断裂和柳林-缺月岭-山龙断裂之间的宿松变质杂岩进行了综合细致的分析,确定了特征性的高压岩石——石榴石-蓝晶石-硬绿泥石片岩的存在。利用THERMOCALC的Average P-T法,确定了石榴石-蓝晶石-硬绿泥石片岩的峰期变质温压条件为T=551~569℃和P=1.96~2.47GPa,属于高压榴辉岩相。LA-ICP-MS锆石U-Pb定年显示该岩石的峰期变质年龄为242.2±2.0Ma,退变质年龄为216.2±6.6Ma。结合区域地质调查和前人的研究成果,该岩石可能普遍存在于这两断裂之间,并暗示了这两断裂之间的块体经历了高压变质作用,其应当从宿松变质杂岩中剥离出来。本文在此暂定名为大山-麻石沟高压块体,并建议宿松变质杂岩的北界止于柳林-缺月岭-山龙断裂。Due to lower metamorphic grade and complexity in lithology,the metamorphic evolution of the Susong Complex has not been widely concerned yet. This has largely hampered profound understanding of the tectonic framework and evolution of the Dabie orogen. In this paper,we present a systematic study of the Susong Complex between the Taihu-Mamiao and Liuling-QueyuelingShanlong faults,and report the discovery of distinctive high-pressure rock-garnet-kyanite-chloritoid schist. Peak metamorphic P-T conditions of the schist were estimated to be 551 ~ 569℃ and 1. 96 ~ 2. 47 GPa using the average P-T approach of the THERMOCALC,pointing to a high-pressure eclogitic facies. The peak and retrograde metamorphic ages can be placed at 242. 2 ± 2. 0Ma and 216. 2 ±6. 6Ma using the LA-ICPMS zircon U-Pb dating technique. Combining with the regional investigation and previously reported data,we predict that this HP schist should extensively exist between the Taihu-Mamiao and Liuling-Queyueling-Shanlong faults. This implies that the whole terrain between the two faults might have undergone high-pressure eclogitic facies metamorphism and should be disintegrated from the Susong Complex. In this paper,we prefer to nominate this terrain as the Dashan-Mashigou high-pressure unit and propose the Liuling-Queyueling-Shanlong fault as the northern boundary of the Susong Complex.

关 键 词：宿松杂岩 石榴石-蓝晶石-硬绿泥石片岩 高压榴辉岩相 峰期变质年龄 大别造山带 

分 类 号：P588.36[天文地球—岩石学]