贵州施秉下翁哨地区镁铝榴石和铬尖晶石自然重砂罕见特高异常查证

    Research on verification of natural heavy sand anomaly of pyrope and chrome spinel in Xiawengshao area, Shibing County, Guizhou Province

    • 摘要: 综合利用以往资料发现,贵州施秉下翁哨地区存在特高浓度镁铝榴石、铬尖晶石等自然重砂异常,且长期未能解释其来源及金刚石找矿指示问题。由于资料形成于“文革”时期,有人怀疑其可靠性,通过针对性的野外调查和采样分析,佐证了该异常的客观存在和以往资料的可靠性。镁铝榴石和铬尖晶石自然重砂含量水平实属罕见,异常区分布于高出现代河床200m的斜坡上部,残积于古河道砂砾石冲积层(?)中,矿物学分析未见重砂矿物明显的搬运磨蚀痕迹,电子探针分析分属于G9镁铝榴石和S5铬尖晶石,应主要来源于石榴和尖晶二辉橄榄岩,系载体母岩——钾镁煌斑岩就近风化残积的结果。

       

      Abstract: A comprehensive utilization of the previous data shows that the placer anomaly with high content of chromium-bearing pyrope and chrome spinel exists in Xiawengshao area, Shibing County, Guizhou Province. The source and diamond exploration problems remain unexplained. Because the previous data were obtained during the "Cultural Revolution" period, the reliability of data is doubtful. Targeted field investigation and sampling analysis prove that the placer anomaly is objective and reliable. The high content placer anomalies are very rarely seen. The anomaly is located in the upper part of the slope which is 200 m higher than the elevation of the modern river bed. Residual deposits were deposited in the alluvial deposits of sand and gravel in the ancient channel. Mineralogical analysis shows no obvious traces of transport and abrasion. Electron microprobe analysis indicates G9 pyrope and S5 chrome spinel, which should be mainly derived from garnet-spinel-lherzolite, being the weathering product of the parent rock-lamproite.

       

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