陕蒙交界地区碎屑岩风化成因浅析     

董恒笔  张清盛  孔文年  朱永宏 《陕西地质》2007,25(2):36-43

陕蒙交界地区基岩均具强风化,由此造成当地环境恶化、下游地区生态破坏和灾害积累。其形成机理应与岩石本身的物质组成、自然地理环境、地质构造状况、水文地质条件及其物理化学条件有关。而南部地区,由于上述诸因素的差别,基岩风化微弱。  相似文献   

Modelling and inversion of single-ended refraction data from the shot gathers of multifold deep seismic reflection profiling—an approach for deriving the shallow velocity structure     

V. Vijaya Rao  Kalachand Sain  V. G. Krishna 《Geophysical Journal International》2007,169(2):507-514

A multifold crustal-scale deep seismic near-vertical reflection profile generates a large number of single-ended shot gathers, which provide redundant data sets because of overlapping coverage of the shallow refractors. We present an approach for deriving the shallow velocity structure by modelling and inversion of single-ended seismic refraction first arrival traveltime data. We apply this method to a data set acquired with a 12-km long spread with 100 m spacing of shots and receivers, of the Neoproterozoic Marwar basin in the NW Indian shield. The approach is shown to be quite successful for delineating the shallow refractor depths, steep dips and velocities, even in the absence of regular reverse refraction profiles. The study reveals two-layered sedimentary formations, Malani volcanics and a complicated basement configuration of the Marwar basin, and provides a measure of resolution and uncertainty of the estimated model parameters. A seismic section of the near-trace gather is found to be qualitatively consistent with the derived structural features of the basin. The relative highs and lows, observed in the Bouguer gravity profile, further corroborate the derived velocity model. The present approach can be especially useful in offshore areas and elsewhere, where the single-ended multifold seismic profiles are the only available data sets.  相似文献   

南秦岭凤凰山地区元古代构造基底特征   总被引：5，自引：0，他引：5  

齐文  王向利  王炜红  王北颖  白定邦  张彪 《陕西地质》2002,20(2):9-19

依据在原划武当岩群中获得的 1 6 86± 4 5Ma (锆石U -Pb)同位素测年资料 ,结合岩石学、岩石地球化学及区域地层对比 ,从中解体出姚坪岩组。通过岩石学、岩石地球化学、构造特征、变质变形特征研究及形成环境探讨认为 :南秦岭凤凰山元古代武当岩群 (包括姚坪岩组、杨坪岩组 )变质火山岩系为古—中元古代时期多岛洋构造环境过渡基底建造 ;耀岭河岩组浅变质火山岩为本区Rodina事件的产物。该成果对南秦岭构造基底的组成、发展、演化研究具有重要意义。  相似文献   

Metamorphism of the Basement of the Qilian Fold Belt in the Minhe-Ledu Area, Qinghai Province, NW China     

TSAI Chinglang  WEI Kunghua  WANG Chenshu Department of Earth Sciences  National Cheng Kung University  Tainan  Taiwan  China 《《地质学报》英文版》2002,76(1):31-43

The basement of the central Qilian fold belt exposed along the Minhe-Ledu highway consists of psammitic schists, metabasitic rocks, and crystalline limestone. Migmatitic rocks occur sporadically among psammitic schist and metabasitic rocks. The mineral assemblage of psammitic schist is muscovite + biotite + feldspar + quartz ± tourmaline ± titanite ± sillimanite and that of metabasitic rocks is amphibole + plagioclase + biotite ± apatite ± magnetite ± pyroxene ± garnet ± quartz. The migmatitic rock consists of leucosome and restite of various volume proportions; the former consists of muscovite + alkaline feldspar + quartz ± garnet ± plagioclase while the latter is either fragments of psammitic schist or those of metabasitic rock. The crystalline limestone consists of calcite that has been partly replaced by olivine. The olivine was subsequently altered to serpentine. Weak deformations as indicated by cleavages and fractures were imposed prominently on the psammitic schists, occasionally on me  相似文献   

Tectonics of Precambrian basement of the Tarim craton   总被引：4，自引：0，他引：4  

GUO Zhaojie  ZHANG Zhicheng  JIA Chengzao  Wei Guoqi 《中国科学D辑(英文版)》2001,44(3):229-236

The Altyn Tagh Mountain is the main area where the Precambrian basements of Tarim craton are exposed. There are two ophiolitic belts in Altyn Tagh: one belt is exposed in the northern margin of Altyn Tagh whose formation age is about (829±60) Ma, the other is situated along the southern margin of Altyn Tagh and has a formation age of about (1449±270) Ma. This paper proposes a simple tectonic model for the Precambrian basement of Tarim craton established from ophiolites in Altyn Tagh area. The south Tarim block had amalgamated with Qaidam block during about 1400-1500 Ma along the present Altyn fault, while the south Tarim-Qaidam united block was still separated from the north Tarim block by an ocean. The united block of south Tarim and Qaidam collided with north Tarim block along the zone of high positive anomaly of central Tarim, Hongliugou and Lapeiquan in about 800 Ma. So since the Sinian (beginning at 800 Ma) there has been an integrated basement for Tarim craton.  相似文献   

再论胶莱盆地金矿的找矿方向——隐伏基底综合信息金成矿预测   总被引：2，自引：2，他引：2  

刘玉强 《中国地质》2001,28(11):13-19

通过1：20万及部分1：5万综合信息成矿预测和对地质、物探、遥感资料解译，认为胶莱盆地隐伏基底区具有胶北隆起出露基底区类似的金成矿地质条件。在建立胶北隆起区已知金矿密集区统计预测模型的基础上进行了定性和定位、定量预测：胶莱盆地有很大的找金潜力，尤其是盆地的东北缘和西北缘找金远景最好。根据预测排序，建议优先部署5个靶区金矿的勘查评价工作。  相似文献   

吉林延边地区斑岩型-浅成热液型金铜矿床   总被引：12，自引：4，他引：12  

芮宗瑶  张洪涛  王龙生  陈仁义  金伯禄  金逢洙  万玉胜  周永昶  孟庆丽 《矿床地质》1995,14(2):99-126

吉林延边地区为我国滨太平洋带的一个重要的金属成矿区，与中生代火山－次火山－侵入活动胶在的斑岩型－浅成热液矿床在时空上，成因上构成一个成矿系列，本文选择四个代表性矿床（小西南岔，闹枝，五凤和刺猬沟），较详细地介绍它们的成矿地质背景，矿床地质特征、流体包裹体，稳定同位素及成矿机制等。通过这些矿床的描述，勾画出一幅从中生代火山盆地边缘的隆起带的斑岩矿床（小西南岔）→中生代火山盆地边缘的隆起带的斑岩型矿岩  相似文献   

Magnetic and Gravity Investigations of Lisan Peninsula-Dead Sea(Jordan)     

BataynehA.  Al-ZoubiA.  HassounehM. 《中国地质大学学报(英文版)》1995,(2)

The Lisan Peninsula is located within the Dead Sea basin which represents the plate boundary between African and Arabian plates. This basin constitutes a good example of a pull-apart basin because of its large dimensions, its structural simplicity and its active subsidence . The gravity data reveal that the Dead Sea basin can be divided into segments, each of them about 30 km long in N-S direction , where the Lisan Peninsula represents the deepest one (9 km thick Pleistocene sediments ), overlying about 6 km thick Mesozoic sediments . In addition , 20 km of extension was predicted along the Dead Sea basin, which indicates that the Dead Sea basin should be about 3.3 Ma in age . Furthermore, the Precambrian basement under the Lisan area is characterized by high susceptibility contrast that is related to continuous tectonic activity in the region.  相似文献   

Development of grabens and associated fault-drags: An experimental study     

Sugata Hazra 《Journal of Earth System Science》1995,104(3):489-498

Experiments on extensional faulting were performed with semi-brittle talc-sand beds resting on a ductile clay base. The experiments show that the development of graben in the talc-sand beds is controlled by the deformation in the ductile basement. Graben-like structures form only when there is a non-uniform stretching in the basement. Uniform extension at the basement level fails to produce any such structures. Grabens initiate as large synclinal structures (sag). The sag is generated either by a downward flexing of the talc-sand bed on a ductile basement or by non ****-uniform thinning of beds. Listric master faults bounding the grabens intersect the basement at high angles. The master faults that initiate as curved shear planes rotate further with continued extension. At the initial stage, the graben structures are associated with normal drags, and with progressive deformation, drag patterns change from normal to a reverse one.  相似文献   

燕山地区长城纪扇三角洲沉积   总被引：3，自引：0，他引：3       下载免费PDF全文

和政军  张新元 《沉积与特提斯地质》1993,(5):36-43

在燕山地区东部的滦县等地,太古代至早元古代结晶基底之上发育一套百余米厚的陆源粗碎屑沉积。长期以来,许多研究者将其与蓟县地区长城系近底部的陆相沉积地层对比,认为属于常州沟组。1980年,钱祥麟等经过系统的研究,提出这套地层为晚长城纪大红峪期的超覆沉积。此后,这套粗碎屑沉积的性质及其与盆地整体沉积环境系统的关系。一直未能确定。近年来,笔者为此进行了初步的沉积学研究,结果表明这套粗碎屑沉积与其上的碳酸盐沉积构成了较为典型的 Gilbert 型扇三角洲沉积相。该扇三角洲沉积的确立,为燕山地区中一晚元古代坳拉槽南东缘盆地界线的限定以及早期盆地拉张过程中的沉积充填方式的研究,提供了重要的依据。  相似文献