三江地区南澜沧江带火山岩构造岩浆类型   总被引：6，自引：4，他引：6  

沈上越  冯庆来  刘本培  莫宣学 《矿物岩石》2002,22(3):66-71

从火山岩地质，岩石组合，岩石化学，稀土元素，微量元素，大地构造环境等诸方面论述了南澜沧江带可细化为5个火山岩构造岩浆带，即大平掌裂谷火山岩带，大兴山-小街洋脊火山岩带，大兴山-热水塘洋内弧火山岩带，邦沙陆缘弧火山岩带，小定西-民乐陆内弧火山岩带，这种细化对探讨该区的特提斯演化有极重要的作用。  相似文献   

Cumulate and Cumulative Granites and Associated Rocks   总被引：1，自引：0，他引：1  

Bruce W. Chappell  Doone Wyborn 《Resource Geology》2004,54(3):227-240

Abstract. Processes that move crystals relative to melt, that is crystal fractionation, are of major importance in producing variations that are observed within cogenetic suites of granites. In low‐temperature granite suites, crystal fractionation initially involves the progressive separation of crystals residual from partial melting from that partial melt. Once separation of those crystals, or restite, has been completed, further fractionation may occur through the separation of crystals that had precipitated from the melt, the process known as fractional crystallization. High‐temperature granite magmas are largely or completely molten and elements such as Ca, Mg and Fe, and their associated minor elements, are in that case dissolved in the melt. Such magmas, particularly those that are more potassic and hence contain a higher fraction of low temperature melt, may evolve compositionally through fractional crystallization. Cumulate rocks result, comprising a framework of cumulus minerals with interstitial melt. In this process some of the melt is also displaced to form more felsic rocks. Such cumulate rocks may have distinctive chemical compositions, but that is often not the case. Distinctive features include SiC>2 contents near or below 50 % in rocks that are transitional in the field to more felsic granites, very high Cr and Ni, very low K, P, Ba, Rb and Zr, and anomalous abundances of the anorthite components Ca and Al. These rocks may also have positive Eu anomalies. Cumulate rocks do not necessarily have distinctive textures, at least as such features are understood at this time. Fractional crystallization can also involve the movement of precipitated crystals relative to melt. We refer to rocks as cumulative when formed from the fractions in which the abundance of crystals has increased. The production of cumulative granites typically occurs at more felsic melt compositions than is the case for cumulate granites, and this process may have its greatest significance in the fractional crystallization of the felsic haplogranites. Relative to felsic granites of broadly similar compositions lying on a liquid line of descent, cumulative granites contain more Ca, reflecting the addition from elsewhere of plagioclase crystals with solidus compositions. The abundances of Sr and Ba may be high to very high, and sometimes there are positive Eu anomalies. Cumulative I‐type granites may have low abundances of Y and the heavy REE, while the S‐type granites can be very distinctive with anomalously high abundances of Th and the heavy REE resulting from the concentrating of monazite. Generally, but not always, those who propose fractional crystallization as a mechanism for producing compositional variation within a suite of granites do not state whether the rocks in that particular case are thought to lie on a liquid line of descent or are cumulates/cumulative, although it is generally presumed that they were melts. Our experiences in eastern Australia have shown that the mechanism of fractional crystallization was quantitatively not as important during granite evolution as many workers would expect. However, there are some excellent examples of that process, most notably the Boggy Plain Supersuite. Overall in eastern Australia, varying degrees of separation of restite is a much more common mode of crystal fractionation, and that may also be seen to be the case for some other granite provinces if they are examined with that possibility in mind.  相似文献   

老挝万象平原钾镁盐矿区开采技术条件研究     

任明忠 《云南地质》2004,23(2):179-187

万象平原丰富的钾镁盐矿产资源正有待开发，正确选择开采方式将能最大限度地保护环境和提高资源利用率。针对盐类固体矿产的两种开采方式——坑道开采(旱采)和水溶开采(水采)，分别从水文地质、工程地质和环境地质三个方面对矿床开采技术条件进行深入评价，研究确定了矿区的开采技术类型以及开采技术条件，并就旱采和水采条件分别进行对比分析，从中择优选取比较理想的水溶开采法——钻孔选择性溶浸法。  相似文献   

环渤海地区及华北平原第四纪古环境变迁机制     

王强  刘立军  王卫东  徐海振  孙维义 《华北地质》2004,27(3):129-138

在青藏高原隆升背景下，环渤海地区与华北平原成为中国东部汇流盆地和堆积平原。第四纪时期阶段性河流进积，造成研究区出现构造气候旋回性的环境变迁。晚更新世以来沿海平原进入一个快速沉降阶段，在全球性冰川海平面变化叠加背景下．研究区水热对流状况以及相应的环境变迁更加剧烈和丰富。在晚全新世河流造陆过程中．河流的沉积速率超过了海平面的上升速率，陆地才得以形成。在现代海岸带依然持续构造沉降、河流输沙减少、相对海平面上升的背景下，认识不同时间尺度环境变迁机制是极其必要的。  相似文献   

三江中段地球化学分区探讨     

魏启荣  沈上越  莫宣学  路凤香 《矿物岩石地球化学通报》2001,20(4):295-297

本文以富集系数Ki 为指标 ,将三江中段划分为 7个地球化学区和 16个地球化学子区。探讨了各地球化学区 (子区 )的地球化学特征以及Au、Ag、Cu、Pb、Zn成矿元素在某些子区的富集特点。  相似文献   

福建平潭岛芦洋埔平原地下水资源开发利用问题   总被引：2，自引：0，他引：2  

林军 《上海国土资源》2001,(Z1):17-20

该文阐述了目前平潭岛的供水现状及存在问题,并阐述了平潭岛芦洋埔平原地质、水文地质条件,以及地下水资源贮存、水质等特征及其富集规律,对地下水资源进行了初步计算,对其水质进行了初步评价,可作为地下水资源开发利用依据.  相似文献   

地质学在湖南省土地利用总体规划（1997—2010）实施中的应用   总被引：1，自引：0，他引：1  

童潜明 《湖南地质》2001,20(2):139-143

以地质体为基础的土壤分类能反映土地的本质，对土地评价和利用及生态环境的保护和建设都具有实际意义；在强化洞庭湖平原区国土综合整治及防止土地废弃和垦复废弃土地等方面，通过地质规律的研究可以起到事半功倍的作用。因此地质学与土地学相交叉的研究，对于拓宽地质学的服务领域和促进土地学的发展都极为有益。  相似文献   

Establishment of wetlands on the southeastern Atlantic Coastal Plain: Paleolimnological evidence of a mid-Holocene hydrologic threshold from a South Carolina pond     

E.E. Gaiser  B.E. Taylor  M.J. Brooks 《Journal of Paleolimnology》2001,26(4):373-391

The series of climatic events affecting landscapes on the southeastern Atlantic Coastal Plain over the past several thousand years is poorly understood. This is due, in part, to the paucity of depositional basins in this region containing adequately preserved microfossils for paleoecological analyses. This research reconstructs past hydrologic environments from the microfossil record of Peat Bay, a small, peat-filled pond in south-central South Carolina. We cored the deepest location in the pond and retrieved 120 cm of sediment representing 5200 yr of deposition. Fine clays at the base of the core resembled sediments deposited in abandoned channels of the nearby Savannah River, suggesting the basin may have functioned as an oxbow wetland prone to periodic flooding and drying. Overlying peats containing planktonic diatom assemblages mark the onset of persistent open-water conditions ca. 4600 B.P. These data, in conjunction with a small body of paleoecological evidence from other southeastern wetlands, suggest that a hydrologic 'threshold' was surpassed during the mid-Holocene that resulted in flooding and expansion of low-lying depressions that characterize the regional landscape. This is likely the culmination of long-term hydrologic trends related to glacial retreat, including increased precipitation and a rise in ground water levels corresponding to a global rise in sea level. In Peat Bay, lake-like conditions persisted until about 3800 B.P., after which time aerophilic diatoms and remains of other temporary pond organisms dominated the fossil record. Episodic drying of pond sediments during the late-Holocene may have been a response to decreased precipitation, stabilization of the water table and infilling of the pond by decaying vegetation and terrigenous clastics. The microfossil record indicates that temporary pond conditions persisted until recent years (ca. 1985) when the basin returned to a permanently flooded state due to groundwater connection to a large reservoir constructed nearby.  相似文献   

云南三江地区富碱侵入岩与煌斑岩的同源性   总被引：8，自引：1，他引：8  

金志升  黄智龙  朱成明 《矿物岩石地球化学通报》1997,(4)

云南三江地区富碱侵入岩与煌斑岩的同源性金志升黄智龙朱成明（中国科学院地球化学研究所，贵阳５５０００２）关键词三江地区富碱侵入岩煌斑岩同源性三江地区富碱侵入岩带（亦称哀牢山－金沙江富碱侵入岩带）是世界上著名的富碱侵入岩带之一，前人对该区富碱侵入岩进行过...  相似文献   

神奇美丽的横断山:地壳演化塑造的奇迹——“三江并流”世界自然遗产地形成地质背景浅析     

王义昭 《地质通报》2006,(Z1)

三江并流是反映地球演化主要阶段的杰出代表,区内保存着反映特提斯演化不同阶段和喜马拉雅期陆内造山阶段留下的丰富的地质遗迹,这些地质遗迹为解读三江并流地壳演化的历史提供了重要的依据。有关资料表明,三江并流是与青藏高原和横断山脉一起发育成长起来的,它们均经历了特提斯的演化,并且都是印度板块与欧亚板块强烈碰撞造山作用的产物。本文比较详细地介绍了横断山脉的形成演化过程及其与青藏高原形成演化之间的关系。  相似文献