摘要
滇西北金沙江缝合带格亚顶—茂顶地区广泛出露一套岩性为绢云母石英片岩、石英岩、斜长角闪岩、二云母石英片岩和大理岩等岩石的变质岩系,该变质岩系的原岩沉积时代存在较大争议。本文对采自其中的绢云母石英片岩和石英岩进行了LA-MC-ICP-MS锆石U-Pb年龄测定,测试表明,其中绢云母石英片岩锆石年龄中最年轻年龄为205 Ma,锆石年龄谱的主峰值为约231 Ma,两个次峰值年龄分别为约214 Ma和约255 Ma,并存在约420 Ma、约502 Ma、约873 Ma、约1.94 Ga和约2.46 Ga的年龄峰;石英岩锆石年龄中最年轻年龄为332 Ma,锆石年龄谱的主峰值为约361 Ma,次峰值为约422 Ma,其它峰值为约1.40 Ga、约1.56 Ga和约1.72 Ga。上述同位素年龄表明绢云母石英片岩原岩的沉积时代应晚于205 Ma,可能为晚三叠世;石英岩原岩的沉积时代应晚于332 Ma,可能为早石炭世。该套变质岩系并非前人认为的元古宙基底。此外,所分析样品的锆石年龄谱还显示该变质岩系的碎屑物质主要来源于扬子陆块。
A suit of metamorphic rock series are largely outcropped in Geyading-Maoding area, Jinsha Suture, northwestern Yunnan Province. The rocks include quartzite, sericite-quartz schist, amphibolites, micaschist and marbles. The depositional age of the metamorphic rock series has long been debated. In this paper, sericite-quartz schist and quartzite are measured by the LA-MC-ICP-MS method. The dating of zircons shows that the detrital zircon ages of sericite-quartz have a youngest age of about 205 Ma, a dominant peak at 231 Ma, two subordinate peaks at 214 Ma and 255 Ma, and some lesser peaks at 420 Ma, 502 Ma, 873 Ma, 1.94 Ga and 2.46 Ga; the detrital zircon ages of quartzite have a youngest age of about 332 Ma, a dominant peak at 361 Ma, a subordinate peak at 422 Ma, and the other lesser peaks at 1.40 Ga, 1.56 Ga, 1.72 Ga. These dating results above suggest the protolith of sericite-quartz schist was deposited in the Late Triassic （later than 205 Ma）, and the protolith of quartzite was deposited in the Early Carboniferous （later than 332 Ma）, which indicate the formation age of the metamorphic rock basement in Geyading-Maoding area, Jinsha Suture, shouldnt be thought to be Proterozoic in age. Besides, the data of detrital zircon population suggest that the provenance of the metamorphic rock series was mainly derived from the Yangtz Block materials.
出处
《地质论评》
CAS
CSCD
北大核心
2013年第6期1131-1142,共12页
Geological Review
基金
国家重点基础研究发展规划(编号2009CB421001)
国土资源部公益性行业科研专项(编号201011027-1C)
中国地质调查局项目(编号1212011121066)的成果
