黔北下寒武统黑色岩系主要由硅质岩、磷块岩、多元素富集层、黑色页岩等组成。采用X射线粉末衍射分析和扫描电镜分析研究了各岩类的矿物成分特征,重点进行了微量元素地球化学研究,黑色岩系微量元素总量在金属富集层之钼矿层达到峰值,显...黔北下寒武统黑色岩系主要由硅质岩、磷块岩、多元素富集层、黑色页岩等组成。采用X射线粉末衍射分析和扫描电镜分析研究了各岩类的矿物成分特征,重点进行了微量元素地球化学研究,黑色岩系微量元素总量在金属富集层之钼矿层达到峰值,显示出在剖面上从下到上先渐次增加后又有所回落的趋势。黑色岩系中Ba、As、Sb等元素的浓集系数普遍较高,高于有关热水沉积物的统计数据,反映出较强的热水沉积作用的特征。各岩类U/Th比值均大于1,钼矿层甚至达119,表明受到较强的热液活动的影响。δU=1 73～1 99>1,表现为缺氧沉积环境。在Zn Ni Co三元图中,也显示了热水沉积的特点。可见,黑色岩系形成于缺氧滞流海盆,热液活动提供了丰富的物质来源。展开更多
The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatopor...The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatoporoids, bryozoans, nearly all tentaculites, a few superfamilies of brachiopods, such as Atrypacea and Pentameracea and some important elements of goniatites, such as Manticoceras.``The end-Frasnian was a phase of mass extinction. A large number of shelly benthos were killed by the F-F event. Early and middle Famennian was the survival interval. The marine faunas were very rare at that time. The late Famennian was the recovery interval. There appeared to have many new taxa in the Strunian stage. It lacked a radiation interval in Late Devonian Famennian because another event (the D-C mass extinction) happened at the Devonian-Carboniferous boundary.``Several causes for the F-F mass extinction have been proposed by some geologists, which have been grouped into two broad types, terrestrial and extraterrestrial. The former is related to sea level changes, climate changes and anoxic water event. The latter is linked with some forms of meteorite impact.``A large-scale eustatic change of sea level and black shales representing an anoxic environment has been invoked to explain one of the causes for the F-F mass extinction.展开更多
Ⅰ. INTRODUCTIONQixia（P<sub>1</sub><sup>1</sup> q） and Gufeng（P<sub>1</sub><sup>2</sup> g） formations of early Permian series were deposited during the maximum trans...Ⅰ. INTRODUCTIONQixia（P<sub>1</sub><sup>1</sup> q） and Gufeng（P<sub>1</sub><sup>2</sup> g） formations of early Permian series were deposited during the maximum transgression periods in the upper Paleozoic. With a thickness of 150—200m, Qixia formation is composed of Liangshan coal seams ～1.5—3 m thick at the bottom, bitumen-bearing thickly-stratified 'stinking limestone' in the lower part, consisting of greyish-black biological clastic micrite and micro-silty limestone. The limestone in the展开更多
文摘黔北下寒武统黑色岩系主要由硅质岩、磷块岩、多元素富集层、黑色页岩等组成。采用X射线粉末衍射分析和扫描电镜分析研究了各岩类的矿物成分特征,重点进行了微量元素地球化学研究,黑色岩系微量元素总量在金属富集层之钼矿层达到峰值,显示出在剖面上从下到上先渐次增加后又有所回落的趋势。黑色岩系中Ba、As、Sb等元素的浓集系数普遍较高,高于有关热水沉积物的统计数据,反映出较强的热水沉积作用的特征。各岩类U/Th比值均大于1,钼矿层甚至达119,表明受到较强的热液活动的影响。δU=1 73～1 99>1,表现为缺氧沉积环境。在Zn Ni Co三元图中,也显示了热水沉积的特点。可见,黑色岩系形成于缺氧滞流海盆,热液活动提供了丰富的物质来源。
基金This work was supported by the Major State Basic Research Projects of China (Grant No.2000077704) the Major Project of the Chinese Academy of Sciences (Gram No. KZ-952-J1-023) the National Natural Science Foundation of China (Grant No. 49872007)
文摘The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatoporoids, bryozoans, nearly all tentaculites, a few superfamilies of brachiopods, such as Atrypacea and Pentameracea and some important elements of goniatites, such as Manticoceras.``The end-Frasnian was a phase of mass extinction. A large number of shelly benthos were killed by the F-F event. Early and middle Famennian was the survival interval. The marine faunas were very rare at that time. The late Famennian was the recovery interval. There appeared to have many new taxa in the Strunian stage. It lacked a radiation interval in Late Devonian Famennian because another event (the D-C mass extinction) happened at the Devonian-Carboniferous boundary.``Several causes for the F-F mass extinction have been proposed by some geologists, which have been grouped into two broad types, terrestrial and extraterrestrial. The former is related to sea level changes, climate changes and anoxic water event. The latter is linked with some forms of meteorite impact.``A large-scale eustatic change of sea level and black shales representing an anoxic environment has been invoked to explain one of the causes for the F-F mass extinction.
文摘Ⅰ. INTRODUCTIONQixia（P<sub>1</sub><sup>1</sup> q） and Gufeng（P<sub>1</sub><sup>2</sup> g） formations of early Permian series were deposited during the maximum transgression periods in the upper Paleozoic. With a thickness of 150—200m, Qixia formation is composed of Liangshan coal seams ～1.5—3 m thick at the bottom, bitumen-bearing thickly-stratified 'stinking limestone' in the lower part, consisting of greyish-black biological clastic micrite and micro-silty limestone. The limestone in the
