DOLOMITE TYPES AND TRACE ELEMENT GEOCHEMISTRY OF THE EARLY PALEOZOIC STRATA IN THE KEPING-BACHU AREA, TARIM BASIN
Through the analysis and determination of stained thin sections, observation of cath-odoluminescence,and testing of trace elements for the early Paleozoic carbonate in the Tarim basin, eight types of dolomites with different textural genesis are recognized. They are micritic-cal-cisiltic dolomite,dolomite with relict texture of limestone,fine planar euhedral-subeuhedral floating matrix dolomite,fine euhedral-subeuhedral dolomite,medium-coarse nonplanar anhedral dolomite, medium planar euhedral-subeuhedral dolomite cement,coarse nonplanar saddle matrix dolomite, and coarse nonplanar saddle dolomite cement respectively. Analysis of trace element geochemistry reveals that these samples are rich in light REE,deficit in heavy REE,with negative Eu anomaly. Samples with relative high trace elements are of great variability, and different samples are of different variable elements. Saddle dolomite is characterized by high Eu positive anomaly, indicating hydrothermal influence. The Ce/Ce* value of calcite is larger than Vindicating influence of detrital material of terrigenous origin. However,the Ce/Ce* value of dolomite is less than 1,demonstrating mantle origin, which can be further evidenced by the values of (La/Ce)N and (La/Yb)N. Saddle dolomite is characterized by low Sr and high Ba content,the former illustrates the diagenetic process and the latter indicates the hydrothermal origin. The Sr/Ba ratios of all samples are larger than Vindicating the hydrothermal influences with variable extent, which is approved by the ratios of U/Th of all samples.
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万方数据
维普
