北京地区侏罗纪岩浆活动对聚煤作用的影响     

杨荣丰  张可能  张鹏飞  刘钦甫  刘新华 《地质科学》2003,38(2):263-266

本文以北京侏罗纪煤田为例详细研究了岩浆活动对聚煤作用的影响。聚煤前、聚煤过程中和聚煤后的岩浆活动对煤系的形成和保存都有影响:煤系形成前和形成过程中的岩浆活动通过控制成煤盆地的基底地形和成煤盆地的水深来影响聚煤作用;煤系形成后的岩浆侵入,使煤系变质并破坏煤层。  相似文献   

U-Pb and Pb-Pb zircon dating of the older orthogneiss suite in the Silvretta nappe,eastern Alps: Cadomian magmatism in the upper Austro-Alpine realm     

Bernhard Müller  Urs Stefan Klötzli  Markus Flisch 《International Journal of Earth Sciences》1995,84(3):457-465

Two orthogneiss suites dominate the Silvretta nappe. Primary crystallization of the larger suite (younger orthogneisses) is assumed to be Ordovician in age. The second, adjacent magmatic suite consists of older, alkaline to calc-alkaline, ultrabasic, basic to intermediate and granitic rocks known as older orthogneisses. U-Pb data of multigrain zircon fractions, as well as single zircon stepwise evaporation ²⁰⁷Pb/²⁰⁶Pb results suggest a latest Proterozoic to early Cambrian intrusion age for the protoliths of the older orthogneisses as both dating methods yield early Cambrian crystallization ages of 526±7 and 519±7 Ma for an alkaline granite gneiss; similar results were obtained for two neighbouring calc-alkaline orthogneisses (²⁰⁷Pb/²⁰⁶Pb ages of 533 ± 4 and 568 ± 6 Ma, respectively). The crystal habitus corresponds to P5, S19 and S9 zircons of magmatic origin. Whole-rock initial Sr isotope ratios indicate a primitive source. The igneous protoliths of these older orthogneisses represent a fragment of a Cadomian (Pan-African) crust found in places within the basement of the European Hercynides.  相似文献   

岩浆作用的物理过程研究进展   总被引：8，自引：0，他引：8  

赖绍聪 《地球科学进展》1999,14(2):153-158

概略地介绍了８０年代以来硅酸盐熔体及硅酸盐晶－液悬浮体的密度、粘度、熔体结构、流全动力学等方面的研究动向,及其对岩浆作用、岩浆运移、岩浆侵位机制的动力学约束条件,硅酸盐熔体的结构是制约熔粘度的主导因素,化学成分对熔体匠控制是通过改变熔体结构而实现的,粘度在一定程度上决定着岩浆的迁移、侵痊和喷发方式。密度和浮力是岩浆上升侵位的重要约束,地壳是岩交涉升的一个密度过滤器岩浆最终由于浮和的消失而停止上升。  相似文献   

北山区域地质发展史和金矿区域成矿模式   总被引：3，自引：0，他引：3  

陈祖伊  张学权  张昭明  束秀琴  何奕强  封全宏 《铀矿地质》1993,(2)

本文通过对北山地区地层、岩浆岩宏观和微观特征的详细研究,论证了北山南带是一个发育于前寒武纪古陆上的陆缘裂陷槽,其3次拉张闭合运动控制了古生代的岩浆活动而使其呈现有序的演化。区内的金及与其伴生的亲铜元素矿产与裂陷糟最后闭合所派生的岩浆热液活动有紧密的成因和空间联系,为其演化的端元产物。在研究本区两大金矿类型(含金石英脉和蚀变岩)的物质成分,共生矿物的标型特征和围岩蚀变的基础上,阐明了北山的主要金矿成矿规律,建立了金矿区域成矿模式。  相似文献   

3-D gravity and magnetic interpretation for the Haifa Bay area (Israel)     

M. Rybakov  V. Goldshmidt  L. Fleischer  Y. Ben-Gai 《Journal of Applied Geophysics》2000,44(4)

Recently observed features in the subsurface geology of the Haifa Bay area (northern Israel) have been evaluated using 3-D forward gravity and magnetic modeling and inversion schemes. The interpretation is based on updated petrophysical data of the Jurassic, Cretaceous and Tertiary sedimentary layers and volcanics. It has been shown that the Bouguer gravity anomalies correspond mainly to thickness variations in the Senonian to Tertiary sediments. The gravity effect of these sediments was calculated using their actual densities and structural setting as interpreted from seismic reflection data. This effect was removed from the Bouguer gravity in order to study the pre-Senonian geological structures. The pattern of residual gravity anomalies (named “stripped gravity”) is essentially different from the pattern of the Bouguer gravity. The prominent Carmel gravity high, clearly seen on the Bouguer gravity map, completely vanishes on the “stripped” gravity map. That suggests that this relatively positive anomaly is caused by the considerable thickness of the low-density young sediments in the surrounding areas and does not correspond to high-density magmatic rocks or crystalline basement uplift as previously suggested. The average densities of the Jurassic and Cretaceous volcanics are generally lower then those of the background sedimentary rocks. Volcanics are the main cause for magnetic anomalies onshore and offshore northern Israel. The magmatic root of the Asher volcanics is, most probably, located close to the Yagur fault. A large, deep-seated gabbroic intrusion is assumed to be located under the Mediterranean abyssal plain in the NW part of the study area. The Atlit marine gravity low appears to be caused by a thick Mesozoic and Tertiary sedimentary accumulation. The results presented should be of considerable assistance in delineating some aspects of hydrocarbon exploration in the area.  相似文献   

滇西三江造山带中段马登盆地两个富碱火山岩的锆石U-Pb定年及地质意义          下载免费PDF全文

韩雪  杨天南  信迪  梁明娟 《贵州地质》2019,36(1):69-76

运用LA-ICP-MS锆石U-Pb同位素定年的方法测定了滇西三江造山带中段马登盆地内的2件富碱火山岩的年龄。结果表明马登盆地内粗安质火山岩形成年龄约在35Ma。富碱火山岩的形成时间与滇西三江造山带南段中东带内的新生代富碱斑岩岩浆作用高峰期一致,同样属于青藏高原后碰撞岩浆作用的时间范围内,这些富碱岩浆岩的岩浆活动是对印度-欧亚大陆巨大碰撞的一种响应。  相似文献   

Secular cooling and crystallization of partially molten Archaean continental crust over 1 Ga   总被引：1，自引：1，他引：0  

Olivier Vanderhaeghe  Célia Guergouz  Cécile Fabre  Stéphanie Duchêne  David Baratoux 《Comptes Rendus Geoscience》2019,351(8):562-573

The protracted tectonic and magmatic record of cratons over the Archaean Eon has been classically interpreted in terms of long-lived shallow-dipping subduction or repeated mantle plumes. In this paper, we use the 1D conductive heat equation to model the evolution of the geotherm of a generic felsic-dominated Archaean cratonic nuclei solely considering the secular decay of radioactive isotopes (²³⁸U, ²³⁵U, ²³²Th, and ⁴⁰K), responsible for heat production in the crust. Using a range of plausible parameters for crustal thickness, lithospheric thickness, and surface heat flux, this modelling shows that Archaean crust was characterized by an initially high geothermal gradient at 3.5 Ga, with a Moho temperature close to 900 °C, and that it might have remained partially molten for about one billion years. The existence of a partially molten crust for an extended period of time offers an alternative option to shallow-dipping subduction or repeated mantle plumes for the understanding of the peculiar tectonic evolution of Archaean cratons marked by (i) protracted high-temperature metamorphism and magmatism associated with crustal differentiation, and (ii) widespread deformation characterized by structural domes attributed to the development of crustal-scale gravitational instabilities.  相似文献   

The passive margin of northern Gondwana during Early Paleozoic: Evidence from the central Tibet Plateau     

《Gondwana Research》2020

The central–south domain of the Tibet Plateau represents an important part of the northern segment of Gondwana during the early Paleozoic. Here we present zircon U–Pb, Lu–Hf isotope, and whole–rock geochemical data from a suite of early Paleozoic magmatic rocks from the central Tibet Plateau, with a view to gain insights into the nature and geotectonic evolution of the northern margin of Gondwana. Zircon grains in four granitic rocks yielded ages of 532−496 Ma with negative ε_Hf(t) values (−13.7 to −0.6). Zircon grains in meta–basalt and mafic gneiss yielded ages of 512 ± 5 Ma and 496 ± 6 Ma, respectively. Geochemically, the granitic rocks belong to high–K calc–alkaline and shoshonitic S–type granite suite, with the protolith derived from the partial melting of ancient crustal components. The mafic gneiss and meta–basalt geochemically resemble OIB (Oceanic Island Basalt) and E–MORB (Enriched Mid–Ocean Ridge Basalt), respectively. They were derived from low degree (∼5–10%) partial melting of an enriched mantle (garnet and spinel lherzolite) that was contaminated by upper crustal components. The parental magmas experienced orthopyroxene–dominated fractional crystallization. Sedimentological features of the Cambrian–Ordovician formations indicate that the depositional cycle transformed from marine regression to transgression leading to the formation of parallel/angular unconformities between the Cambrian and Ordovician strata. The hiatus associated with these unconformities are coupled with the peak of the early Paleozoic magmatism in Tibet Plateau, indicating a tectonic control. We conclude that the Cambrian–Ordovician magmatic suite and sedimentary rocks formed in an extensional setting, and we correlate this with the post–peak stage of the Pan–African orogeny. The post–collision setting associated with delamination, orogenic collapse or lithospheric extension along the northern margin of Gondwana, can account for the Cambrian–Ordovician magmatism and sedimentation, rather than oceanic subduction along the external margin. We thus infer a passive margin setting for the northern Gondwana during the Early Paleozoic.  相似文献   

阴山地块晚太古代岩浆作用、变质作用对地壳演化及BIF成因的启示   总被引：6，自引：5，他引：1  

马旭东  范宏瑞  郭敬辉 《岩石学报》2013,29(7):2329-2339

阴山地块是华北克拉通西部太古代基底出露最大最完整的地区.固阳地区是阴山地块最具代表性的地区,主要由中西部低级别变质的晚太古代花岗-绿岩地体和东部的高级变质杂岩地体组成.统计结果表明,无论是绿岩带,花岗岩类侵入体,还是高级别变质杂岩的原岩都形成于晚太古代末期(2562 ～ 2510Ma),形成时间上相互重叠,在～2500Ma,～2480Ma分别经历了两期变质事件,第一期为逆时针的P-T轨迹,与洋脊俯冲有关;第二期则表现顺时针的P-T轨迹,与晚期碰撞造山有关.科马提岩-科马提质玄武岩、高镁安山岩-富Nb火山岩、TFG和Sanukitoid多种具有特殊构造意义的岩石同时发育.综合已有资料获得如下启示,阴山地块在晚太古代受板块体制控制,并先后经历了洋脊俯冲和碰撞造山过程.将区域内的BIF与相关岩石联系起来考虑,得出BIF的形成与洋脊俯冲有关,BIF中的Si来源于绿岩带底部的玄武岩,Fe来源于同层位的科马提岩.  相似文献   

Neogene magmatism and its possible causal relationship with hydrocarbon generation in SW Colombia     

Mónica Vásquez  Uwe Altenberger  Rolf L. Romer 《International Journal of Earth Sciences》2009,98(5):1053-1062

The Cretaceous oil-bearing source and reservoir sedimentary succession in the Putumayo Basin, SW Colombia, was intruded by gabbroic dykes and sills. The petrological and geochemical character of the magmatic rocks shows calc-alkaline tendency, pointing to a subduction-related magmatic event. K/Ar dating of amphibole indicates a Late Miocene to Pliocene age (6.1 ± 0.7 Ma) for the igneous episode in the basin. Therefore, we assume the intrusions to be part of the Andean magmatism of the Northern Volcanic Zone (NVZ). The age of the intrusions has significant tectonic and economic implications because it coincides with two regional events: (1) the late Miocene/Pliocene Andean orogenic uplift of most of the sub-Andean regions in Peru, Ecuador and Colombia and (2) a pulse of hydrocarbon generation and expulsion that has reached the gas window. High La/Yb, K/Nb and La/Nb ratios, and the obtained Sr–Nd–Pb isotopic compositions suggest the involvement of subducted sediments and/or the assimilation of oceanic crust of the subducting slab. We discuss the possibility that magma chamber(s) west of the basin, below the Cordillera, did increase the heat flow in the basin causing generation and expulsion of hydrocarbons and CO₂.  相似文献