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371.
湘鄂黔桂毗邻区扬子地台基底与第一盖层之探讨 总被引:1,自引:0,他引:1
毗邻区黄陵背斜裸露的崆岭群,系太古界结晶基底。该结晶基底上的冷家溪群,梵妆山群和四堡群为下元古界褶皱基底,并具“P型克拉通”之基底结构。而神农架群,板溪群,下江群与丹洲群,均属毗邻区地台之第一个盖层。基底与盖层是高角度不整合界面,系武陵造山运动的记录。 相似文献
372.
鄂尔多斯盆地基底结构特征及其对古生界天然气的控制 总被引:26,自引:0,他引:26
鄂尔多斯盆地位于华北克拉通西部,是我国大型含油气盆地之一。基底结构复杂,具有显著的下均匀性,基底断裂数量多,规模大,基底顶面表现为两个大型隆起,北部为伊盟隆起,中南部为中央古隆起,盆地基底结构对上覆沉积盖怪岩性,岩相具明显控制作用,从而间接影响到油气的生成,运移与聚集。伊盟隆起地抽侧斜坡及中央古隆起四周斜坡地带,是寻找古生界天然气的有利场所;盆地中南部几条NE向大型韧性剪切带,可能地油气分布产生重要影响,在油气勘探中也应给予重视。 相似文献
373.
Some geophysical surveying works in the northeast part of Dandong, such as shallow shock refracted wave, electrical prospecting,
electrical sounding and wave velocity measuring, are introduced in this paper, and the dynamic parameters are calculated.
The results show that the basement structure in surveying region is very complex, the overburden thickness of the quaternary
period, velocity distribution and dynamic parameters are of regional characteristics. The depth of basement is deep in the
north and shallow in the west, the difference between north and west region is about 5–10 m. The south part of Yalu river
fault belt is composed of F1, F2, F3, F4, F5 fault, their strike direction is NE, we can determine that the F2 fault is the main one in Yalu river fault belt, and the south part of Yalu river fault belt has no activity since Holocene
Epoch.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 282–288, 1993. 相似文献
374.
375.
376.
Reaction textures and fluid behaviour in very high pressure calc-silicate rocks of the Münchberg gneiss complex, Bavaria, Germany 总被引:2,自引:0,他引:2
Calc-silicate rocks occur as elliptical bands and boudins intimately interlayered with eclogites and high-pressure gneisses in the Münchberg gneiss complex of NE Bavaria. Core assemblages of the boudins consist of grossular-rich garnet, diopside, quartz, zoisite, clinozoisite, calcite, rutile and titanite. The polygonal granoblastic texture commonly displays mineral relics and reaction textures such as post kinematic grossular-rich garnet coronas. Reactions between these mineral phases have been modelled in the CaO-Al2O3-SiO2-CO2-H2O system with an internally consistent thermodynamic data base. High-pressure metamorphism in the calc-silicate rocks has been estimated at a minimum pressure of 31 kbar at a temperature of 630d? C with XH2, O ≥ 0.03. Small volumes of a CO2-N2-rich fluid whose composition was buffered on a local scale were present at peak-metamorphic conditions. The P-T conditions for the onset of the amphibolite facies overprint are about 10 kbar at the same temperature. XCo2 of the H2O-rich fluid phase is regarded to have been <0.03 during amphibolite facies conditions. These P-T estimates are interpreted as representing different stages of recrystallization during isothermal decompression. The presence of multiple generations of mineral phases and the preservation of very high-pressure relics in single thin sections preclude pervasive post-peak metamorphic fluid flow as a cause of a re-equilibration within the calc-silicates. The preservation of eclogite facies, very high-pressure relics as well as amphibolite facies reactions textures in the presence of a fluid phase is in agreement with fast, tectonically driven unroofing of these rocks. 相似文献
377.
集宁以东火山岩铀成矿带是一个较有远景的成矿带。本文在概要的阐述区域地质背景的基础上,着重讨论了该带的火山作用及其与板块活动的关系,提出了火山盆地分类和命名的基本原则。根据这些原则对本区火山盆地进行了较系统的分类,并归纳和总结了它们的基本特征及区域铀矿化的主要特点。指出本区铀成矿的火山盆地是上叠塌陷式、上叠沉陷式和上叠断陷式火山盆地,并分析了它们成矿的有利条件。在上述分析讨论的基础上,对本区区域成矿条件进行了综合分析,预测了一类成矿远景区有六个火山盆地,二类远景区有八个火山盆地,并指出了它们的找矿方向。 相似文献
378.
Syn-deformational migmatites and magmatic-arc metamorphism in the Xolapa Complex, southern Mexico 总被引:1,自引:0,他引:1
The Xolapa Complex (XC) is the largest plutonic and metamorphic mid‐crustal basement unit in Mexico and represents an ancient continental magmatic‐arc. A complete range from metatexite to diatexite migmatitic structures has been produced during a single high‐grade metamorphic event. However, structural relics reveal the existence of early Cpx + Pl + Qtz ± Opx and Grt + Opx + Pl + Qtz ± Cpx pre‐migmatitic metamorphic assemblages. Field relationships and microstructural observations allow us to constrain five pre‐, syn‐ and post‐migmatitic deformational phases. It is argued that migmatitic structures and minor anatectic granites were developed during ductile recumbent folding and shear structures related to the D2–D3 phases. Late post‐migmatitic ductile‐brittle deformation is evidenced by the development of NNE trending transpressional thrusting (D4), and E–W left‐lateral mylonitic shear zones (D5). Biotite‐breakdown melting in felsic rocks and amphibole‐breakdown melting in mafic rocks, as well as geothermobarometric results, indicate that metamorphism took place at temperatures from 830 to 900 °C and pressures ranging from ≥6.3 to 9.5 kbar. Late migmatitic assemblages equilibrated in the highest temperature range along a clockwise P–T path. The relationships between the large diversity of migmatitic structures and the progressive production of melt suggest that feedback relations prevailed as a time‐marker during a contractional regime. Deformation, metamorphism, and plutonism of the XC show that this terrane evolved as a north‐east‐verging thrust system with synkinematic metamorphism and partial melting, during the Late Cretaceous – Palaeogene. The tectonothermal history of XC is analogous to a Cordilleran metamorphic magmatic‐arc formed in an accretionary tectonic framework. This new model provides constraints on the exhumation mechanism and thermal evolution of southern Mexico. 相似文献
379.
Nonconventional hydrocarbon targets in the crystalline basement, and the problem of the recent replenishment of hydrocarbon reserves 总被引:1,自引:0,他引:1
Analysis of the distribution of oil pools in sedimentary cover has shown that known platform hydrocarbon fields are closely associated with faults in the crystalline basement and the sedimentary cover itself. Oil pools in the lower productive beds of the sedimentary cover are linked to faulted zones in the crystalline basement. A genetic relationship between oil fields and tectonic dislocations indicates a dominant role for vertical migration in the accumulation of commercial hydrocarbons in the Paleozoic. The conducted geochemical, palynological, geophysical and geological studies have shown that oil and gas pools in the upper sedimentary cover have been formed due to the vertical migration of hydrocarbons, which is also confirmed by the vertical alignment of the oil pools. 相似文献
380.
本文对松潘-甘孜和西秦岭造山带地球物理特征以及基底构造进行了研究。研究表明:松潘-甘孜地块与西秦岭造山带的基底性质相似,均具有扬子块体的构造属性。褶皱基底的分布范围为:西南部以二道沟-玉树-理塘为界;东至青川-都江堰,即龙门山断裂带;北部边界由西到东,沿昆仑南缘至花石峡,然后转向北东,沿兴海-夏河-西和展布。在深地震测深和高温、高压岩石密度研究结果的约束下对重力资料进行反演,得到该地区的基底起伏。反演结果表明:松潘-甘孜-西秦岭地区的基底深度为1.3~8.6km(以海平面起算)。阿坝-甘孜-道孚以及夏河-泽库-兰州一带为基底隆起区;若尔盖-唐克-红原、花石峡达日和-达日东南一带为基底凹陷区,其中红原附近基底深度达8.6km,为全区基底深度最大的地方。 相似文献