桐庐杂岩体中共存的两种碱性长石研究          下载免费PDF全文

陈小明  刘昌实等 《地质论评》2001,47(3):317-321

桐庐同熔型火山－侵入杂岩中出现两种碱性长石，一种为无色透明，另一种为微红色，本文利用X射线衍射仪，电子探针，透射电镜对其结构态，成分及出溶微结构进行了对比研究。结果表明，两者成分差别不大，而结构差别较大，无色透明的为透长石，出溶叶片发育；微红色的为正长石或低透长石，出溶结构不发育。而且随着冷却速率的变慢，无色透明碱性长石的Al/Si有序度增大，微红色碱性长石的有序度降低，分析后认为这种共存现象是岩浆混和造成的，从而为桐庐杂岩体的岩浆混合成因提供了有力的证据。  相似文献   

Geochemical Characteristics and Genesis of Late Cretaceous to Paleogene Basalts in the Tuyon Basin, South Tianshan Mountains     

WANG Yanbin  WANG Yong  LIU Xun  FU Derong  XIAO Xuchang  QI Longshui . Institute of Geology  Chinese Academy of Geological Sciences  Beijing . Hebei College of Technology  Tangshan 《Continental Dynamics》2001,(1)

1. Introduction The Tianshan Mountains is a typical intercontinental orogenic belt in the world. From late Carboniferous to Permian, the old Tianshan formed during the tectonic amalgamation of the Tarim block, Tianshan block and Siberia craton (Carroll et al, 1990). Mid-Cenozoic basalts are widely distributed in both the Tuyon basin of southwest Tianshan and its western part of Tianshan in Jierjisi in late Cretaceous-Paleogene period, which indicates the activation of the old Tianshan.…  相似文献   

峨眉山玄武岩与铅锌矿床成矿关系初探—以云南会泽铅锌矿床为例   总被引：31，自引：4，他引：31  

黄智龙  陈进  刘丛强  韩润生  李文博  赵德顺  高德荣  冯志宏 《矿物学报》2001,21(4):681-688

本文以云南会泽铅锌矿为例，从成矿时代、成矿物来源、成矿流体来源和成矿热动力等方面初步讲座主峨眉山玄武岩与铅锌矿床成矿的关系。结果表明：矿床成矿时代可能与峨眉山玄武岩岩浆活动时代相近；峨眉山玄武岩在成矿过程中提供了部分成矿物质；伴随峨眉山玄武岩岩浆活动过程去气作用（包括地幔去气作用和岩浆去气作用）形成的流体参与了会泽铅锌矿成矿流体的形成；峨眉山玄武岩岩浆活动为成矿热动力的主要来源。  相似文献   

峨眉山玄武岩的岩相与岩体结构   总被引：16，自引：0，他引：16  

沈军辉  王兰生  徐林生  李天斌 《水文地质工程地质》2001,28(6):1-4

峨眉山玄武岩是西南地区水电工程的主要建基岩体，其岩体结构明显受其建造的控制，不同地区，不同岩相的玄武岩，由于岩石组合及原生结构特征等的差异，而具有不同的岩体结构特征。本文结合拟建金沙江溪洛渡水电工程，雅砻江官地水电工程等实例，从岩相角度分析了玄武岩岩相及原生结构及原生结构对其岩体结构的控制作用。  相似文献   

Geochemistry and magnetostratigraphy of deccan flows at Anjar, Kutch     

A. D. Shukla  N. Bhandari  Sheela Kusumgar  P. N. Shukla  Z. G. Ghevariya  K. Gopalan  V. Balaram 《Journal of Earth System Science》2001,110(2):111-132

Chemical analysis of nine Deccan flow basalts at Anjar, Kutch, western India, indicates that all, except the uppermost flow F-9, are alkaline. In their major and trace element composition, the alkali basalts resemble Ocean island basalts (OIB). Similarities of many diagnostic trace element ratios (e.g. Sm/Nd, Ba/Nb,Y/Nb and Zr/Nb) are similar to those found in the Réunion Island basalts. The uppermost basalt is tholeiitic and chemically resembles the least contaminated Deccan basalt (Ambenali type). The Anjar basalts have iridium concentration ranging between 2 and 178 pg/g. Some of these values are higher by about an order of magnitude compared to the Ir concentration in other basalts of the Deccan. A synthesis of chemical, palaeomagnetic and geochronologic data enables us to construct a chemical and magnetic stratigraphy for these flows. The three flows below the iridium enriched intertrappean bed (IT III) show normal magnetic polarity whereas all except one of the upper basalts show reversed magnetic polarity. The sequence seems to have started in polarity zones 31N and probably continued up to 28R or 27R. The results presented here support the view that Deccan volcanism in Kutch occurred on a time span of a few million years.  相似文献   

Generation of Deccan Trap magmas   总被引：1，自引：0，他引：1  

Gautam Sen 《Journal of Earth System Science》2001,110(4):409-431

Deccan Trap magmas may have erupted through multiple centers, the most prominent of which may have been a shield volcano-like structure in the Western Ghats area. The lavas are predominantly tholeiitic; alkalic mafic lavas and carbonatites are rare. Radioisotope dating, magnetic chronology, and age constraints from paleontology indicate that although the eruption started some 68 Ma, the bulk of lavas erupted at around 65–66 Ma. Paleomagnetic constraints indicate an uncertainty of ± 500,000 years for peak volcanic activity at 65 m.y. in the type section of the Western Ghats. Maximum magma residence times were calculated in this study based on growth rates of “giant plagioclase” crystals in lavas that marked the end phase of volcanic activity of different magma chambers. These calculations suggest that the > 1.7 km thick Western Ghats section might have erupted within a much shorter time interval of ∼ 55,000 years, implying phenomenal eruption rates that are orders of magnitude larger than any present-day eruption rate from any tectonic environment. Other significant observations/conclusions are as follows: (1) Deccan lavas can be grouped into stratigraphic subdivisions based on their geochemistry; (2) While some formations are relatively uncontaminated others are strongly contaminated by the continental crust; (3) Deccan magmas were produced by 15–30% melting of a Fe-rich lherzolitic source at ∼ 3–2 GPa; (4) Parent magmas of the relatively uncontaminated Ambenali formation had a primitive composition with 16%MgO, 47%SiO₂; (5) Deccan magmas were generated much deeper and by significantly more melting than other continental flood basalt provinces; (6) The erupted Deccan tholeiitic lavas underwent fractionation and magma mixing at ∼ 0.2 GPa. The composition and origin of the crust and crust/mantle boundary beneath the Deccan are discussed with respect to the influence of Deccan magmatic episode.  相似文献   

四川冕西稀土成矿区的地质特征及其远景探讨   总被引：2，自引：0，他引：2  

李钟发  蒋明全 《地质科技情报》1992,11(3):51-58

笔者从区域地质条件、矿床地质特征、冕西岩体性质、稀土模式、主要稀土矿物特征以及矿石的工艺性质进行了考查,并作了区域性对比。初步认为,在冕西地区以碱长花岗体为主体,形成了面积近800km~2的稀土成矿区。霓石碱性花岗岩-构造破碎带-碱性(伟晶)岩脉是区内稀土成矿的基本要素,也是最直接的找矿标志,围绕冕西岩体出露的卫星式霓石碱性花岗岩有着不同于A型碱长花岗岩的稀土模式,是稀土成矿矿源体。不同产地的稀土矿物特征、矿石矿物组合和矿石类型均有很好的可比性,属易采易选优品级稀土矿石。在该区有必要进一步开展矿产普查工作。  相似文献   

新生代黄骅坳陷构造伸展、沉积作用和岩浆活动   总被引：15，自引：1，他引：15  

孟庆任  王战  王翔  解建民 《地质论评》1993,39(6):535-547

黄骅坳陷是一典型的张性盆地,其构造主要受西缘向东倾的拆离断层的控制。构造沉降分析显示盆地西部以裂谷沉降为主,而向东热沉降逐渐增大,反映了上地壳的强烈裂谷区与岩石圈深部强烈减薄区发生了错位。沉积作用在裂谷期和热沉降期具明显不同的特点,指示了早期基底快速不均匀的下沉和晚期基底广泛缓慢下沉的过程。玄武岩的形成和演化也与盆地构造发展过程相一致。研究结果表明,黄骅坳陷是在下伏岩石圈上部发生简单剪切和下部发生纯剪切的构造伸展过程中形成的。  相似文献   

物理探查方法在土壤改良中的应用研究   总被引：4，自引：0，他引：4  

郭秀军  章光新  谭笑平 《地理科学》1999,19(5):470-474

如何快速全面的了解整个改良区的土层分布情况及盐碱化程度,如何对改良的效果进行了有效的检测,是盐碱地改良工作中的所要解决的问题,应用物理探查的方法解决这些问题,证实其在盐碱地的改良工程中是一种可行,有效的方法,并拟在国家“九五”重点科技攻关项目专题－松嫩平原盐碱地综合治理与农业持续发展研究中采用此项技术方法,进行跨学科的技术应用研究。  相似文献   

Permian radiolarians,chert and basalt from the Daxinshan Formation in Lancangjiang belt of southwestern Yunnan,China   总被引：2，自引：0，他引：2  

Qinglai?FengEmail author  Shangyue?Shen  Benpei?Liu  Dietrich?Helmcke  Xianggui?Qian  Weiming?Zhang 《中国科学D辑(英文版)》2002,45(1):63-71

The stratigraphical sequences composed of chert and basalt were found in the Daxinshan area of Simao and the Manbie area of Jinghong, southwestern Yunnan. The Middle Permian to ealiest Late Permian radiolarians, such as Follicucullus and Pseudoalbaillella, have been identified from the chert. The chert from the Manbie area of Jinghong is characterized by high SiO₂content (over 92%), large ratios of MnO/TiO₂ (2.15) and low ratios of Al/(Al+Fe+Mn) (≤0.1) and Ce/Ce*(0.4), which indicate that the chert was deposited in pelagic basin. The chert from the Daxinshan area of Simao, however, is characterized by low SiO₂ content, low ratios of MnO/TiO₂ (0.27) and high ratios of Al/(Al+Fe+Mn) (0.49) and Ce/Ce*(0.88), which imply that the chert was deposited in continental margin basin. The basalts from the both areas belong to tholeiite series, and the chemical compositions of their major, rare earth and trace elements show the characteristics of MORB. These results evidence that there are volcanic rocks and chert sequences representing pelagic basin and oceanic basin near continent. These sequences and the formerly reported island-arc volcanic rock sequences imply that the Daxinshan Formation in the Lancangjiang belt represents a sedimentary assemblage formed in active continental margin basin.  相似文献