秦岭大别碰撞造山带根部结晶基底隆升的变质岩石学证迹   总被引：1，自引：0，他引：1       下载免费PDF全文

游振东  钟增球  韩郁菁  桑隆康  陈能松  张泽明 《地球科学》1997,6(3)

秦岭大别碰撞造山带中隆升最高的结晶基底便是大别杂岩，在超高压变质岩和某些高级变质岩中均发现典型的近等温减压（ＩＴＤ）型的退变质结构，多呈后成合晶或冠状体的形式取代或包绕原生矿物晶粒（主晶），显示退变质不平衡反应的过程．然而超高压变质岩与大别杂岩中的高级变质岩，变质地温梯度截然不同，暗示它们形成的构造条件极不相同，超高压变质岩早期由岩石圈深处（１２０ｋｍ±）折返到下地壳与那里的高级变质岩构造混合，平行并置，而后才一起隆升．退变质不平衡结构与寄主岩的面理无关，说明这种近等温的减压退变质作用发生于后造山时期近绝热条件下的隆升体制，近绝热隆升的热源可能是中生代以来大别山地区岩石圈减薄所引起  相似文献   

论造山运动的时间特征   总被引：8，自引：0，他引：8       下载免费PDF全文

张传恒  王自强 《地质学报》1997,71(1):18-26

造山运动是指会聚板块边缘岩石圈构造加厚形成山带的过程,对其时间特征的认识历来存有争议。造山带变形构造研究表明,逆冲断裂是控制造山带发展、演化的主要变形机制,逆冲断裂扩展的方向性、序次性和长期性使笔者确信,造山运动是一个延续可达几十百万年的长期、分阶段的发展过程。造山运动发展阶段性主要表现为主逆冲断裂带的转换和变形速率的变化。角度不整合形成机制和空间转换规律分析进一步证实了上述认识。“长期性”和“阶段性”是造山运动时间特征的两个不可分割的侧面。前陆盆地是研究造山运动的关键地区之一。  相似文献   

Three-dimensional numerical simulations of crustal deformation and subcontinental mantle convection     

L.-N. Moresi  A. Lenardic 《Earth and Planetary Science Letters》1997,150(3-4):233-243

3-D simulations of mantle convection allowing for continental crust are explored to study the effects of crustal thickening on lithosphere stability and of continents on large-scale mantle flow. Simulations begin with a crustal layer within the upper thermal boundary layer of a mantle convection roll in a 1 × 1 × 1 Cartesian domain. Convective stresses cause crust to thicken above a sheet-like mantle downwelling. For mild convective vigor an initial crustal thickness variation is required to induce 3-D lithospheric instability below the zone of crustal convergence. The amplitude of the required variation decreases with increasing convective vigor. Morphologically, instability is manifest in formation of drip-like thermals that exist within the large-scale roll associated with initial crustal thickening. A strong surface signature of the drips is their ability to cause deviations from local Airy compensation of topography. After the initial thickening phase, the crustal accumulation that forms serves as a model analog to a continent. Its presence leads to mantle flow patterns distinctly different from the steady-state roll that results in its absence. Large lateral thermal gradients are generated at its edge allowing this region to be the initiation site for continued small-scale thermal instabilities. Eventually these instabilities induce a restructuring of large-scale mantle flow, with the roll pattern being replaced by a square cell. Although preliminary and idealized, the simulations do show the fluid dynamical plausibility behind the idea that significant mantle variations can be generated along the strike of a largely 2-D mountain chain by the formation of the chain itself. The ability of a model continent to cause a change in fundamental convective planform also suggests that the effects of continental crust on mantle convection may be low-order despite the seemingly trivial volume of crust relative to mantle.  相似文献   

秦岭造山带泥盆系热水沉积岩相应用研究及实例   总被引：9，自引：0，他引：9  

方维萱  张国伟等 《沉积学报》2001,19(1):48-54

构造-热水沉积岩相与盆地的古地理环境,热水沉积岩相与热水沉积成矿,热 (水 )流体岩相与构造背景、构造古地理,它们之间有密切地内在联系.应用热水沉积岩相、沉积相及沉积体系分析方法,对凤县铅硐山-双石铺三级构造热水成矿盆地进行研究.  相似文献   

云南中西部喜马拉雅期岩浆及成矿研究新进展   总被引：7，自引：2，他引：7  

罗君烈  李志伟 《云南地质》2001,20(3):229-242

云南中西部喜马拉雅期分为4个构造幕，其岩浆侵入活动反映两个热旋回，当岩浆侵入活动结束后才出现火山喷发高潮。笔者首次将新生代内生成矿作用划分为6个时间序列。根据岩石类型组合、侵位时限、成矿专属性，首次将富碱斑岩分为6个超单元、18个单元，从7个方面总结各单元、超单元特征。对富碱斑岩和其它4类岩浆岩进行了演化规律的对比。探讨金顶超大型铅锌矿床与各类岩浆岩的成因关系，详细论述了铅同位素和惰性气体的最新资料并加以对比，初步认为两者深部物源与形成过程有本质上的重要联系，金顶及兰坪盆地内的热水矿床是一套与地幔及幔壳混合有一定关联的独立成矿作用。  相似文献   

再论陆内型造山作用   总被引：3，自引：0，他引：3       下载免费PDF全文

赵宗溥 《地质科学》1996,31(4):353-364

目前流行的半真实、半虚假的新全球构造学说已经给中国大陆地质研究带来一定的困惑和困难。中国大陆各地质时代发生的造山作用皆属陆内型。用地体说、碰撞说、地缝合线说和安第斯造山模式论述青藏高原的形成、演化史是地质研究的几个误区。秦岭-大别山属陆内型造山带,其形成与板块构造无关,采用壳-幔拆离构造的造山机制可解释超高压变质岩的生成。超高压变质岩是识别岩石圈收缩引起的一系列地质事件最有效的标志。  相似文献   

攀西地区喜马拉雅期碱性杂岩的稀土成矿条件及资源特点   总被引：4，自引：0，他引：4  

施泽民  李小渝 《四川地质学报》1996,(1)

讨论了攀西地区稀土矿源体和稀土矿赋存体组成的喜马拉雅期碱性杂岩的特征、成矿条件和稀土资源特点，指出该地区稀土矿床是与幔源偏酸碱性岩浆成因有关的中低温脉状充填型稀土矿床。  相似文献   

Geochronology of the mid-German crystalline rise west of the River Rhine     

Thomas Reischmann  Gerald Anthes 《International Journal of Earth Sciences》1996,85(4):761-774

The mid-German crystalline rise has its westernmost exposures at the western margin of the Rhine graben in the southern Pfalz and the northern Alsace. The outcrops are made up of granitoid rocks and minor volcano-sedimentary sequences. Radiometric ages obtained by U/Pb, Pb/Pb, Sm/Nd and Rb/Sr analyses of the igneous rocks from this area range from ∼433 to ∼325 Ma thus covering a time span from the Silurian to the end of the lower Carboniferous. Because the investigated rocks are — according to their chemical composition — largely related to subduction zone environments, the following three geodynamical scenarios are postulated, always taking subduction of oceanic crust beneath the mid-German crystalline rise into account: (a) subduction of the Rheic ocean during the Silurian from the north; (b) subduction of the Rhenohercynian ocean during the late Devonian (∼369 Ma) from the north; (c) subduction of the Saxothuringian ocean during the lower Carboniferous (∼334 Ma) from the south.  相似文献   

论扬子地台西缘喜马拉雅期斑岩型铜矿的找矿前景     

李粒主 《四川地质学报》1996,(1)

盐源西苑坪—模范村喜马拉雅期石英二长斑岩群的发现和肯定对认识该区大陆板内岩浆成矿作用及找矿工作具有特殊意义。浅部验证坑道已获斑岩型细脉浸染状铜矿体。模范村是第一个被确定的斑岩型金银铜矿床，这不仅对四川而且对云南在今后寻找该成矿带同类矿床具有借鉴和指导作用，不久的将来必会有一批同类矿床发现。本文就其构造背景、地质特征及找矿前景作简要论述，并对菁河－程海成矿带的其它斑岩群的找矿前景予以预测。  相似文献   

造山与成盆作用形成于统一的动力学机制   总被引：10，自引：0，他引：10  

邓乃恭  任希飞 《地质论评》1996,42(4):300-303

造山带和盆地成因是当前地学研究的两个热点。本文第一部分简述了多种主要造山理论和成盆学说;其中挤压造山说与拉张成盆论在众多学说中仍占主导地位。一般都认为造山带和盆地形成于不同的地球动力学环境。第二部分结合我国地质实际,提出了造山和成盆作用形成于统一的动力学环境,即他们的形成是由于挤压后效——拉张-均衡造山、成盆。  相似文献