红赐堡—黄土窑一带孔兹岩系中石榴石的演化史及其地质意义     

刘福来 《吉林大学学报(地球科学版)》1996,(3)

红赐堡—黄土窑一带早前寒武纪孔兹岩系经历一期麻粒岩相变质作用，并可划分四个变质阶段。各阶段石榴石的分布、形态、矿物组合、化学成分及其成因条件均存在明显差异。通过成因矿物学的系统研究，结合多种地质温压计的估算结果及变质反应实验资料，确定本区孔兹岩系石榴石的结晶生长演化史及变晶变形序列。  相似文献   

The Uplift of the Longmenshan Thrust Belt and Subsidence of the West Sichuan Foreland Basin   总被引：8，自引：0，他引：8  

Liu Shugen  Luo Zhili  Dai Sulan  Changlu Institute of Technology  Chengdu  Sichuan  ChinaDennis Arne Dalhousie U niversity  Canadaand C.J.L. Wilson Melbourne U niversity  Australia Jiang M inxi 《《地质学报》英文版》1996,70(1):16-26

Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e  相似文献   

Structural studies and their bearing on the Early Precambrian history of the Dharwar tectonic province,southern India     

K. Naha  R. Srinivasan  D. Mukhopadhyay 《Journal of Earth System Science》1996,105(4):379-412

In the Dharwar tectonic province, the Peninsular Gneiss was considered to mark an event separating the deposition of the older supracrustal Sargur Group and the younger supracrustal Dharwar Supergroup. Compelling evidence for the evolution of the Peninsular Gneiss, a polyphase migmatite, spanning over almost a billion years from 3500 Ma to 2500 Ma negates a stratigraphic status for this complex, so that the decisive argument for separating the older and younger supracrustal groups loses its basis. Correlatable sequence of superposed folding in all the supracrustal rocks, the Peninsular Gneiss and the banded granulites, indicate that the gneiss ‘basement’ deformed in a ductile manner along with the cover rocks. An angular unconformity between the Sargur Group and the Dharwar Super-group, suggested from some areas in recent years, has been shown to be untenable on the basis of detailed studies, A number of small enclaves distributed throughout the gneissic terrane, with an earlier deformational, metamorphic and migmatitic history, provide the only clue to the oldest component which has now been extensively reworked.  相似文献   

Accretion and exhumation at a Variscan active margin, recorded in the Saxothuringian flysch     

J. Schäfer  H. Neuroth  H. Ahrendt  W. Dörr  W. Franke 《International Journal of Earth Sciences》1997,86(3):599-611

The Saxothuringian flysch basin, on the north flank of the Central European Variscides, was fed and eventually overthrust by the northwestern, active margin of the Tepla-Barrandian terrane. Clast spectra, mineral composition and isotopic ages of detrital mica and zircon have been analyzed in order to constrain accretion and exhumation of rocks in the orogenic wedge. The earliest clastic sediments preserved are of early Famennian age (ca. 370?Ma). They are exposed immediately to the NW of the suture, and belong to the par-autochthon of the foreland. Besides ultramafic (?ophiolite) material, these rocks contain clasts derived from Early Paleozoic continental slope sediments, originally deposited at the NW margin of the Saxothuringian basin. These findings, together with the paleogeographic position of the Famennian clastics debris on the northwestern passive margin, indicate that the Saxothuringian narrow ocean had been closed by that time. Microprobe analyses of detrital hornblendes suggest derivation from the “Randamphibolit” unit, now present in the middle part of the Saxothuringian allochthon (Münchberg nappes). Detrital zircons of metamorphic rocks formed a little earlier (ca. 380?Ma) indicate rapid recycling at the tectonic front. The middle part of the flysch sequence (ca. early to middle Viséan), both in the par-autochthon and in the allochthon, contains abundant clasts of Paleozoic rocks derived from the northwestern slope and rise, together with debris of Cadomian basement, 500-Ma granitoids and 380?Ma (early Variscan) crystalline rocks. All of these source rocks were still available in the youngest part of the flysch (c. middle to late Viséan), but some clasts record, in addition, accretion of the northwestern shelf. Our findings permit deduction of minimum rates of tectonic shortening well in excess of 10–30?mm per year, and rates of exhumation of ca. 3?mm/a, and possibly more.  相似文献   

湖相沉积物与全球变化的研究     

ＤｏｕｇｌａｓＦ．Ｗｉｌｉａｍｓ 《地学前缘》1997,(Z1)

为预测未来全球的气候变化，必须了解在过去水圈、气圈与生物圈的各自作用以及它们是如何相互影响的。为此，ＩＧＢＰ（国际地圈－生物圈计划）组织了过去全球变化项目（ＰＡＧＥＳ）。湖相沉积物保存着与ＰＡＧＥＳ有关的不同时空尺度的丰富的地球系统历史信息，特别是湖相沉积物包含着可以说明全球气候变化的水圈与生物圈的陆源组分的反应。这种信息对了解影响气候变化的流域是如何发展的至关重要。笔者应用西伯利亚贝加尔湖与中国西北部青海湖作为两个实例，叙述了多学科研究湖相沉积物物理与化学参数，并利用这些参数测定了晚更新世湖区及其流域对过去气圈的变化以及日幅射分布的影响  相似文献   

地史转折期的生态系   总被引：7，自引：2，他引：7  

殷鸿福  童金南 《地学前缘》1997,(Z2)

生态系的演变是地球各圈层系统耦合关系变化的直接标志。地史转折期的生态系具有复杂的生物内涵，在绝灭—残存—复苏过程中，各生物类别的演替遵循着一定的生存型式。大绝灭后生态系复苏的原动力是绝灭后迁入避难所的复活类型和大绝灭末期高压环境中产生的祖先类型的新生和辐射发展。全面了解绝灭后生态系的组成和结构，对于正确认识地史转折期，即圈层耦合结点处的地质作用型式和过程具有重要作用。  相似文献   

在1996年南方油气勘探工作会议上的讲话(主要部分) 努力实现南方海相油气勘探重大突破     

周永康 《海相油气地质》1997,(1)

南方地质条件有四方面的特点:碳酸盐岩区与特提斯域有关,具有良好的含油气前景;叠置在碳酸盐岩区上的南、北两大前陆盆地带,对古生界原型盆地烃源岩的演化、油气藏形成和保存起到重要作用;南方海相地层具有丰富的烃源岩;后期多旋回构造运动,使南方海相油气系统变得十分复杂。南方油气选区评价的关键是保存条件,在含油气系统中“保存单元”是优选勘探目标的重要依据。“九五”期间,一要主攻中、下扬子区,获重大突破;二要积极做好滇黔桂地区三个盆地(南盘江盆地、楚雄盆地、十万大山盆地)的预探;三要进一步搞好区域评价。  相似文献   

四川盆地碳酸盐岩油气勘探实践与认识   总被引：2，自引：0，他引：2  

陈季高 《海相油气地质》1997,2(2):22-30

四川盆地烃源十分丰富。但油气演化程度高,大多已进入高成熟和过成熟阶段,至今只在侏罗系发现有油藏,三叠系及其更老地层皆为气藏。储层主要为碳酸盐岩,其特点是低孔低渗,平均孔隙度仅1.7%,平均渗透率小于1×10~(-3)μm~2,但其中的“孔洞发育层段”平均孔隙度可达3%～6%。根据四十年的勘探经验,加强预探并争取新发现是四川盆地油气勘探发展的关键。预探中,按构造带规划大中型气田勘探目标,将成藏条件相似、地域上相邻的局部圈闭群作为一个整体勘探对象,实行稀井广探,少井高效。“八五”以来,在高陡构造带勘探技术、储层横向预探技术等方面有长足的进步,勘探成效不断提高,实现了资源序列的良性循环。  相似文献   

黄土斜坡地震动时程分析          下载免费PDF全文

李忠生 《地震工程学报》2004,26(2):126-130

应用地震危险性分析理论和地震动人工合成技术，给出Newmark法中所需的地震动时程，解决了斜坡稳定性分析Newmark法中难以选取合适地震动时程的难题。通过对黄土斜坡实例计算，给出了坡体中地震动峰值加速度与深度的关系；在计算坡体位移时，提出了等效峰值加速度的概念；对比了使用地面地震动时程和使用坡体内等效地震动时程的计算结果。  相似文献   

岩层离距图法研究沉积岩断裂发育史——以松辽盆地敖古拉断裂为例     

雷茂盛  林静薇 《海相油气地质》2004,(Z1)

利用断裂活动过程中留下的各种地质标记研究断裂发育史是比较困难的 ,已有的研究方法主要可归纳出七种 ,都存在局限性。岩层离距图法是以地震剖面为基础 ,将穿过断裂的各剖面上的标志层投影到沿断裂走向的铅垂面上 ,得到多组标志层的垂向断距数据 ,然后用下部各标志层的断距减去最上部标志层的断距 ,并作多轮次计算 ,直到最后的断距差近似为零或仅剩一个非零标志层。每一轮次计算代表一个活动期次 ,如果出现负值 ,则表示有构造反转。对松辽盆地敖古拉断裂作了实例计算 ,结果为该断裂发育经历了三个正断活动期和一个逆断活动期 ,与盆地区域性活动有些差别。岩层离距图法比起其他已有方法 ,可靠程度大大提高  相似文献