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911.
The Upper Permian Sedimentary Facies and Its Role in the Dajing Cu-Sn Deposit, Linxi County, Inner Mongolia, China 总被引:3,自引:1,他引:3
Gongjiong QIN Yosuke KAWACHI Liqing ZHAO Yongzheng WANG Qiang OU 《Resource Geology》2001,51(4):293-305
Abstract: Exhaustive investigations were launched for confirming the upper Permian host rocks of the Dajing Cu-Sn Deposit, probing into the possibility that Dajing is a Sedex type deposit during cosedimentation, complementing the deficiency of previous researches and going further into substantiating the role of the upper Permian strata in the control of ore distribution. After more than two years work, we reclassified the sedimentary facies in the Dajing area and its periphery as shallow fresh water lake and delta. Indicative sedimentary structures, such as ripple marks, rain marks, and mud cracks combined with contemporary fossils, were revealed. Having measured the flow directions, performed chemical comparison, and analyzed various sediments from sourceland in the Dajing area by XRF, we consequently redivided the strata into four sedimentary members, among which P2 l1 and P2 l2 were concluded as significant ore-hosted strata. The upper Permian basin was a lateral rift basin. The water and sediments in the basin are much deeper and thicker in the north than those in the south.
The indicators of special sedimentary facies, such as gravity flow, brine pool and synchronogenic stratiform structure of the ore cannot be found in the Dajing area. There was no growth fault, assemblage of sulfide and sulfate, and no zonation as well.
On the basis of study in this area, taking into account the paleosedimentary environment as capriciously flowing shallow lake, which approximated the state of oxidation, we figured that the paleogeography made it prohibitively difficult to form stratiform sulfide deposits which are prone to form in deoxidized environment. It can be ruled out the possibility that the Dajing deposit is a syngenetic deposit during sedimentation. 相似文献
The indicators of special sedimentary facies, such as gravity flow, brine pool and synchronogenic stratiform structure of the ore cannot be found in the Dajing area. There was no growth fault, assemblage of sulfide and sulfate, and no zonation as well.
On the basis of study in this area, taking into account the paleosedimentary environment as capriciously flowing shallow lake, which approximated the state of oxidation, we figured that the paleogeography made it prohibitively difficult to form stratiform sulfide deposits which are prone to form in deoxidized environment. It can be ruled out the possibility that the Dajing deposit is a syngenetic deposit during sedimentation. 相似文献
912.
论地质环境的保护与治理 总被引:1,自引:0,他引:1
人类社会的生存和发展,必然开发利用国土资源,从而造成对地质环境的扰动,因此,我们应从发展变化的观点看待地质环境,减少对地环境的坡坏,加强地质环境的治理。 相似文献
913.
五大连池火山群的构造环境与喷发机理 总被引:2,自引:0,他引:2
五大连池火山群位于松辽裂谷的北端,这里的火山活动同裂谷的形成与发展密切相关五大连池火山区发育着典型的“X”型断裂,其次是经向张断裂和纬向压断裂,它们是同一应力场作用下的产物,本文提出了“X”型断裂的形成与发展过程,并认为五大连池区处于“X”型断裂发展的第二阶段,即处于剪切应力的最大值阶段,两组断裂呈正交。 相似文献
914.
915.
华北山地地貌面与新生代构造运动 总被引:6,自引:2,他引:6
华北山地有三期山地夷平面,四期河流阶地面。表明新生代地壳运动具有垂直差异性质。以上升运动为主,平均升幅1700m,速度0.031mm/a。以第四纪为最大。全区新地壳构造形迹可划分为3大类,8亚类和32个小类。在新生代构造运动中,又划分出第四纪以来的新构造运动和晚更新世以来的最新构造运动。 相似文献
916.
伊乐藻—草鱼圈养复合生态系统中水生生物的变化和影响 总被引:2,自引:1,他引:2
从细菌、浮游植物、浮游动物、底栖动物和有机碎屑等几个方面分析了养鱼对伊乐藻种植区(以下简称为有草区)和无草区水域环境的影响。结果表明:两个区域存在着显著的差异性。有草区由于生长着茂密的水生植被,对环境压迫的缓冲能力增强,水生生物的群落结构较为稳定,物种多样性指数高于无草区,有机物的沉降速率也大大低于无草区。与此相比,无草区对环境压迫的缓冲能力较差,水体浮游植物数量增加,富营养化加剧。通过本项实验可以看出,人工种植伊乐藻对养鱼区水质有着明显地控制作用,是发展生态渔业的一条有效途径。 相似文献
917.
新疆沿亚欧大陆桥地带的水环境与持续发展 总被引:1,自引:0,他引:1
本文讨论了新疆沿亚欧大陆桥地带的水环境状况及其特点,以及水环境保护与持续发展的关系。 相似文献
918.
分析了采自南极布兰斯菲尔德海峡海槽中PC10孔(753cm长)的39个样品,共鉴定有孔虫14属21种。有孔虫埋藏可分为硅质壳、钙质壳和混合壳组合。硅质壳组合代表正常的深海沉积环境,反映了相对弱的海底水动力条件;钙质壳组合是浊流沉积的产物,反映了很强的海底水动力条件;混合壳组合则代表趋于正常的深海沉积环境,反映了由强渐弱的海底水动力条件。晚第四纪以来,本区经历了暖-冷-暖的气候变化过程。 相似文献
919.
920.
Geomorphology of a beach-ridge complex and adjacent lake basins along the northern shore of Lake Michigan records fluctuations in the level of Lake Michigan for the last 8000 to 10 000 14C yr B.P. (radiocarbon years Before Present). A storm berm at 204.7–206 m (671.6–675.9 ft) exposed in a sandpit provides evidence of a pre-Chippewa Low lake level that is correlated with dropping water levels of Glacial Lake Algonquin (c. 10 300–10 100 14C yr B.P.). Radiocarbon dates from organic material exposed in a river cutbank and basal sediments from Elbow Lake, Mackinac Co., Michigan, indicate a maximum age of a highstand of Lake Michigan at 6900 14C yr B.P., which reached as high as 196.7 m (645 ft), during the early-Nipissing transgression of Lake Michigan. Basal radiocarbon dates from beach swales and a second lake site (Beaverhouse Lake, Mackinac Co.) provide geomorphic evidence for a subsequent highstand which reached 192.6 m (632 ft) at 5390±70 14C yr B.P.Basal radiocarbon dates from a transect of sediment cores, along with tree-ring data, and General Land Office Surveyor notes of a shipwreck, c. A.D. 1846, reveal a late-Holocene rate for isostatic rebound of 22.6 cm/100 radiocarbon years (0.74 ft/100 radiocarbon years) for the northern shore of Lake Michigan, relative to the Lake Michigan-Lake Huron outlet at Port Huron, Michigan. Changes in sediment stratigraphy, inter-ridge distance, and sediment accumulation rates document a mid- to late-Holocene retreat of the shoreline due to isostatic rebound. This regression sequence was punctuated by brief, periodic highstands, resulting in progressive development over the past 5400 14C yr of 75 pairs of dune ridges and swales each formed over an interval of approximately 72 years. Times of lake-level fluctuation were identified at 3900, 3200, and 1000 14C yr B.P. based on changes in inter-ridge spacing, shifts in the course of Millecoquins River, and reorientation of beach-ridge lineation. Soil type, dune development, and selected pollen data provide supporting evidence for this chronology. Late-Holocene beach-ridge development and lake-level fluctuations are related to a retreat of the dominant Pacific airmass and the convergence of the Arctic and Tropical airmasses resulting in predominantly meridional rather than zonal air flow across the Great Lakes region.This is the 13th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers. 相似文献