合肥盆地早侏罗世防虎山组沉积岩碎屑锆石的矿物包裹体及内部结构

MINERAL INCLUSIONS AND INTERNAL STRUCTURES OF DETRITAL ZIRCONS FROM LOWER JURASSIC SEDIMENTERY ROCKS OF THE FANGHUSHAN FORMATION IN THE HEFEI BASIN

防虎山组的下部砂岩地层是合肥盆地最古老的中生代沉积地层,在样品FH4中选出了碎屑锆石,通过显微激光拉曼光谱、电子探针的研究发现,锆石中含有柯石英、绿辉石、多硅白云母等典型的高压超高压(HP UHP)矿物包裹体、熔体玻璃包裹体以及磷灰石、石英、斜长石、白云母等矿物包裹体。结合阴极发光图像所揭示的锆石内部结构的分析以及锆石的微区测年数据,对碎屑锆石的物源进行了讨论。HP UHP矿物包裹体在具有三叠纪年龄的变质碎屑锆石中的发现,进一步证明大别造山带高压-超高压岩石在早侏罗世时期已经出露地表并为合肥盆地提供了重要物源;碎屑锆石内部结构及成因的多样性表明当时作为源区的大别造山带岩石的复杂性。

In the detrital zircon sample FH4, which was collected from lower sandstones of the Fanghushan Formation, the oldest sedimentary strata of the Hefei Basin.HP-UHP mineral inclusions such as coesite, omphacite, phengite and melt inclusions, and other minerals like apatite, quartz, feldspar, white micas were identified by means of micro-laser Raman spectrometer and electron probe. In combination with the analysis of zircon internal structure revealed by CL images and SHRIMP dating results, the provenance of detrital zircons was discussed. The discovery of HP-UHP mineral inclusions in detrital zircons of Triassic age further proved that the HP-UHP rocks of the Dabie Orogen had been already exposed to the earth's surface in the early Jurassic time, and provided an important source for the Hefei Basin. The diversity of internal structure and genesis of detrital zircons indicated that the source rocks in the Dabie orogen are complicated at that time.