| 库车前陆盆地古近纪—新近纪盐湖环境变迁及其成钾效应探讨 |
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| 关键词:Tarim Kuqa foreland basin Paleogene Neogene evaporite |
| 基金项目:国家“973”计划项目(编号: 2011CB403007)；国家科技支撑计划课题(编号: 2006BAB07B06)；塔里木油田公司科技项目(编号: 41005050002) |
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| Discussion on Paleogene-Neogene Environmental Change of Salt Lakes in Kuqa Foreland Basin and Its Potash-forming Effect |
| Evaporites with large thickness were formed in Kuqa foreland basin during Paleogene-Neogene period.The paleo-salt lake deposits during Paleocene were mainly distributed in central and estern Baicheng depression in the west of Kuqa Basin; then the paleo-salt lake deposits expanded into almost entire Baicheng depression and both depocenter and brine enrichment center of salt lake located in the north part during Eocene; after that the salt lake deposits were still distributed in the most of the depression during Oligocene, but evaporites and brine enrichment center had already moved to its south, and hence the previous tectonic pattern of the half-graben basin characterized by “deep in the north and shallow in the south” was remarkably altered; finally, with the migration of the depocenter from Baicheng depression to Yangxia depression in the east of the basin during Miocene, the salt lake sediments also moved eastward. The brine enrichment centers occured as bead distribution during Paleocene to Miocene. The evolution of paleogeography of Kuqa basin indicated that the development and migration of sub-depression was strongly influenced by tectonic activities in the baisn, which controled the paleogeography of salt lake (e.g. depocenter, material source and brine enrichment center) and might have played an important role in the later potential formation of potash deposits. Further analysis reveals that enrichment tendency for potassium in evaporite sequence also controlled obviously by the paleogeographic changes of the Basin, namely, potassium enrichments should have occurred in the regions with large area and great thickness of the salt deposits. The fact that, potassium content of salt rock cuttings in some oil drill holes gradually increased from the bottom to the top, for example, in the western Baicheng depression, the maximum values of potassium content are 1.07%, 1.43%, 3.05% upward in one drill hole, and in the eastern Yangxia depression, the potassium content varies from 0.008% to 0.152%, was just the geochemical response to the enrichment trend of potassium content controlled by change of lithofacies and paleogeography in the paleo-salt lake. From the above, it can predict that the Kuqa foreland basin has good potash metallogenic prospects, which might exist in brine enrichment center of Baicheng depression in Eocene time and probably migrate to the center of Yangxia depression in Miocene time. |
| LIU Cheng-lin,CAO Yang-tong,YANG Hai-jun,JIAO Peng-cheng,GU Qiao-yuan.2013.Discussion on Paleogene-Neogene Environmental Change of Salt Lakes in Kuqa Foreland Basin and Its Potash-forming Effect[J].Acta Geoscientica Sinica,34(5):547-558. |
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