湘中晚泥盆世晚期两个古群落分析：兼论晚泥盆世古群落的演替和取代     

赵兵 《矿物岩石》1993,13(3):86-94

本文分析了Li群落和C-H群落的生物组成,分异度,相对丰富度,生活方式及空间分布等特征;讨论了湘中晚泥盆世群落的演替和取代规律及其空间对比,进一步强调了生物与环境的密切关系及其在地层学上的意义。  相似文献   

煤层注水的水气驱替理论研究   总被引：7，自引：0，他引：7  

宋维源  李大广  章梦涛  潘一山  孙超 《中国地质灾害与防治学报》2006,17(2):147-150

煤层注水是世界上煤矿矿井防治冲击地压的首选措施。而注水时间、流量、压力等注水工艺参数选择是决定注水防治冲击地压效果的关键。煤层注水过程中水在煤层中渗流的规律是选择注水工艺参数的理论依据。由于煤层孔隙、裂隙中充满气体,煤层注水实际上是水替代气的水驱气的渗流过程。但迄今为止的研究均视为水在煤体中渗流的研究。与实际相距甚远。论文首先分析了煤层注水防治冲击地压的机理,注水使得煤层软化,达到峰值强度后煤体抵抗变形能力随应变降低的幅度减小,即强度后应力-应变曲线变缓。然后根据煤层注水是水驱气过程,将煤层注水视为水气驱替的有动界面的渗流问题研究。将煤层视为各向同性的孔隙介质,分别按照水驱气由钻孔径向周边流动的平面径向流和由钻孔沿煤层平行流动的平面平行流两种情况,建立了水驱气的微分方程,给出了定解条件,并进行求解,得到了不同时间水锋面到达的位置即水注满煤层孔隙的范围。从而可以根据需要注水的范围求出需要提前的注水时间和注水量。为煤层注水预防冲击地压的工艺参数选择提供了科学依据和理论支撑。  相似文献   

Functional substitution of coordination polyhedron in crystal structure of silicates     

叶大年  D.Pushcharovsky  施倪承  马哲生  赫伟  李哲 《中国科学D辑(英文版)》2002,45(8):702-708

On the bases of the study of comparative crystal chemistry of silicates it has been concluded that the octahedra and square pyramids of Ti-0 and Zr-0 play functional role of tetrahedra of Si-0 in the construction of crystal structures. Therefore, those silicates may be named titano-and zircono-silicates. Because of the functional similarity of coordination polyhedra, the structures of cristobalite and feldspar have been compared with those of perovskite and garnet, respectively. As a new concept, the functional replacement of tetrahedra by octahedra and/or pyramids is defined by the authors of this paper for favorable comparison of relative crystal structures.  相似文献   

原生白云石与交代白云石晶体的微结构对比研究   总被引：1，自引：0，他引：1       下载免费PDF全文

杨守业  黄志诚  陈智娜 《岩石矿物学杂志》1997,16(4):362-366

应用高分辨的透射电镜（ＴＥＭ）对原生白云石与交代白云石晶体微结构进行了对比研究。原生白云石晶体中微结构以位错、调制结构为主，调制结构规则，调制波长稳定，属生长调制；交代白云石晶体中的调制结构很不规则，波长变化大，有方解石残留。能谱分析显示两种白云石晶体中调制区与非调制区Ｃａ、Ｍｇ相对含量相差很大。两者微结构差异反映了成因上的不同  相似文献   

陕西旬北浅变质岩区的大型层滑构造   总被引：2，自引：0，他引：2  

陈松岭  黄震 《西北地质科学》1997,18(2):26-32

笔者着重探讨陕西西旬北地区志留系和泥盆系浅变质岩的构造特征，发现这两套地层在构造式要上有明显的差异，它们存在着大型的顺层滑动构造－层滑构造，层滑构造面上下的两套地层是相对独立的构造变形单元。  相似文献   

Mineralogical correlation between primary and replacement dolomites     

Zhicheng Huang  Shouye Yang  Zhina Chen 《中国科学D辑(英文版)》1997,40(1):91-98

Primary dolostones occur in the Upper Sinian Dengying Formation. Based on mineralogical study the indicators for correlation between the primary dolomites which are not influenced by the diagenesis and the replacement dolomites of different periods have been obtained. It is shown that the primary dolomites are characterized by crystal forms precipitated and deposited directly from sea water, stable and homogeneous distribution of Mg and Ca, ideal chemical composition, regular modulated microstructures, low positive δ¹³C and low negative δ¹⁸O. Project supported by the “85–102” Chinese National Key Science and Technology Project.  相似文献   

Multi-textured garnets from a single growth event: an example from northern Norway   总被引：1，自引：0，他引：1  

A.H.N. RICE  D. ROBERTS 《Journal of Metamorphic Geology》1988,6(2):159-172

Abstract Textural relationships between porphyroblasts of biotite and garnet in metasediments in the Nordkinn Peninsula area of the Finnmarkian Caledonides of North Norway are apparently complex. There is evidence for two textural zones in both mineral phases and superficially the development of these appears to have overlapped, at least in part, in time and space. This apparently complex porphyroblast growth history can be considerably simplified if only one period of garnet growth occurred and if different inclusion fabrics developed where garnet replaced biotite porphyroblasts and where it overgrew the matrix foliation. The possibility that porphyroblasts with textural evidence for multiphase growth histories actually grew during a single crystallization event is of importance in the interpretation and elucidation of tectonometamorphic relationships.  相似文献   

砂-砂砾换基防治渠道冻胀的研究     

朱强  付思宁  武福学 《冰川冻土》1988,(4)

本文依据140组渠道工程上的实测数据,建立了残留冻胀率与换填比间的定量关系,据此得出了在地下水深埋和浅埋两种情况下,不同土质所要求的换填比。同时根据冻胀试验场220组粗粒土敏感性试验资料得出,当冻层与地下水距离大于或小于50cm时,应分别控制砂砾料内含土量不大于10％和5％。文末提出了防治砂砾料被含砂渠水污染及设立排水设施以保证换填防冻效果的两项措施。  相似文献   

福建省莆田忠门地区硅线石成因     

张兴洲  贺同兴 《吉林大学学报(地球科学版)》1988,(4)

本文对福建忠门地区中生代变质岩中硅线石的产状、形成阶段及成因方式作了较详细地研究。该区出现的硅线石多属交代成因,不能作为划分变质相的标志。  相似文献   

Carbonate alteration of the Upper Mount McRae Shale beneath the martite-microplaty hematite ore deposit at Mount Whaleback, Western Australia     

Adam D. Webb  Gerald R. Dickens  Nicholas H. S. Oliver 《Mineralium Deposita》2004,39(5-6):632-645

The formation of large martite-microplaty hematite ore deposits in northwest Australia remains a contentious topic in part because important evidence supporting a unifying genetic model has not been observed at all deposits. Carbonate replacement of silica has been found along normal faults below ore at the Mount Tom Price and Giles Mini deposits, which suggests an early hypogene process during ore formation. However, such rocks have not been identified at the largest martite-microplaty hematite deposit, Mount Whaleback. In this study, samples of the Mount McRae Shale are examined for their chemistry, mineralogy and petrography. These samples were collected from several key locations, including an area that immediately underlies ore along the Mount Whaleback fault at Mount Whaleback. Compared to unaltered black Mount McRae Shale from Wittenoom Gorge in the north and altered black and red Mount McRae Shale at Mount Whaleback, reddish-green Mount McRae Shale along the Mount Whaleback fault is greatly enriched in MgO and CaO and depleted in SiO₂. This chemistry arises from significant amounts of fine- to medium-grained ferroan-dolomite and ankerite and cross-cutting chlorite and carbonate veins. The composition is distinct from that produced during regional metamorphism, and most likely represents hydrothermal alteration after metamorphism. The lack of carbonate-rich, silica-poor rocks in the overlying Dales Gorge Member at Mount Whaleback is consistent with pervasive oxidation of most rocks in the region during or after ore genesis, a process that removed carbonates. Although several questions remain unanswered, these results support models that invoke an early hypogene stage during the formation of the martite-microplaty hematite deposits in the Hamersley Province.Editorial Handling: B. Lehmann  相似文献