摘要:
五道梁地区位于青藏高原北部可可西里盆地东部,其中新世发育一系列古湖泊,保存有大套碳酸盐沉积。本文通过对五道梁北山含叠层石剖面和南部剖面进行矿物学、元素地球化学研究,发现叠层石剖面主要矿物为方解石和少量石英,而南侧剖面则含有铁白云石、方解石、石英和钠长石。铁白云石和钠长石次生加大边的发现说明该区曾受热水活动的影响。元素分析结果也显示 As、Sb、Ba、Fe 等热水沉积标志元素含量较高,且Ni/Co、Mn/Sr、V/Cr、V/Sc等比值也较高;加之稀土元素配分模式和碳氧同位素特征均表明该地区为热水湖相沉积。另外叠层藻的出现也反映当时湖水温度至少为20~30℃。综合各种分析结果说明五道梁群为热水湖相成因,该区中新世发育有大量火山岩,因此可作为下一步寻找火山沉积型硼矿床重要线索。
Abstract:
Located in Hoh Xil basin in the north of the Tibetan Plateau, Wudaoliang area possesses a lot of carbonate deposits. The authors studied the mineralogy and element geochemistry of the sediments from the south and north sections of Wudaoliang. The main mineral is calcite with a small amount of quartz in the north sections, while there are ankerite, calcite, quartz and albite in south section. According to the discovery of ankerite and secondary enlarged pore-fringes in albite, the authors hold that Wudaoliang area was affected by hydrothermal activity. The characteristic elements such as As, Sb, Ba, Fe, and the ratios like Ni/Co, Mn, Sr/Cr, V, V/Sc are relatively high. The REE patterns and the carbon and oxygen isotope characteristics also indicate the hydrothermal activities. The emergence of the laminated algae also reflects the water temperature of at least 20 to 30℃. The results obtained by the authors suggest that the Wudaoliang Group is lacustrine hydrothermal sediments. In addition, a large number of volcanic rocks were developed in Miocene, which can be used as the important clues to finding the volcano-sedimentary boron deposits.
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