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法库地区十间房超单元花岗岩岩石成因及侵位机制探讨 总被引:2,自引:0,他引:2
法库地区十间房片麻状二长花岗岩过去被认为是太古代或元古代混合岩和混合花岗岩,1:5万地质调查表明,该花岗岩是与印支一海西湖韧性剪切构造同期侵位的花岗岩,同位素年龄测试属中三叠世,该岩体属复式岩体,是上部地宙沉积物质局部熔融的花岗岩浆沿剪切带被动侵位的“S”型大型岩床。 相似文献
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广昌付坊花岗岩地质特征及侵位机制 总被引:7,自引:0,他引:7
付坊花岗岩出露在武夷山西坡中段。在1:5万广昌县幅区调工作中,通过对其岩性、化学万分、结构、构造等演化特征的研究,将其划分为洋背、高洲、胡竹、太和、石咀圩5个单元,归并为一个超单元;根据其U-Pb法同位素年龄确定其侵位时代为晚奥陶世,属加里东造山期岩浆活动的产物;侵位机制属早期底辟、晚期轻气球膨胀强力型主动就位。 相似文献
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九岭花岗岩是华南地区出露面积最大的一个花岗岩基,长期以来一直被地质工作者所关注。文章以岩浆动力学理论为指导,对九岭岩体选择典型岩体分布区进行构造解析,探讨新元古代花岗岩岩浆活动与构造的关系,分析侵入岩的侵位机制。 相似文献
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白马尖超单元组合特征及其成因机制 总被引:7,自引:0,他引:7
经详细填图,将白马尖复式杂岩体解体出91个侵入体,归并6个单元,3个超单元,它们均属燕山期产物,物源于壳幔混合岩浆。岩石由花岗闪长岩二长花岗岩钾长花岗岩方向演化,岩浆活动由弱强弱,一幕一幕向上推进,呈向北东迁移趋势。区域构造活动和岩浆自身演化的双重因素制约了白马尖超单元组合。 相似文献
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大别山金鸡寨花岗岩体岩石化学特征及侵位机制初步探讨 总被引:2,自引:0,他引:2
】大别山金鸡寨花岗岩体位于大别山碰撞造山带东端,紧邻郯庐断裂,是由碱长石英正长岩和碱长花岗岩组成。这两种岩石的组成矿物均为碱性长石、石英、斜长石、角闪石、黑云母、磁铁矿及副矿物榍石、磷灰石,但矿物含量不同。它们的岩石化学特征也不相同:(1)碱长石英正长岩中常量元素的平均含量(wt%)SiO2为67.11%,Al2O3为17%,Na2O+K2O为10.97%,其中K2O>Na2O,微量、稀土元素均较富集,但高场强元素、轻稀土含量及LREE/HREE均大于碱长花岗岩中的相应数值。(2)碱长花岗岩中常量元素的平均含量(wt%)SiO2为75.13%,Al2O3为13%,Na2O+K2O为8.23%,其中K2O>Na2O,微量、稀土元素含量较高,但大离子亲石元素、重稀土元素含量则大于碱长石英正长岩中的含量。根据野外调查、岩石学特征及常量、微量、稀土元素研究表明,这两种岩石是同一岩浆不同演化阶段的产物,是于造山后形成的A型花岗岩,其形成经历了部分熔融和结晶分异两个阶段,源岩可能来自于北大别变质杂岩。金鸡寨岩体的侵位是以“半汽球”膨胀机制进行的,并与龙井关断裂密切相关。 相似文献
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闾山岩体地处华北板块北缘,天山-兴蒙造山带东段,总体呈北北东方向展布.早期可能受华北板块与佳蒙板块作用,为岩体的形成提供热源与空间;后期华北板块与太平洋板块的作用,使得岩浆最终就位.在板块相互作用的情况下,早期以挤压作用为主,造山作用使得地壳先加厚,后期转化为伸展作用,在地幔热源作用下进行拆沉作用,使得地壳减薄,形成闾山变质核杂岩和东西两侧的断陷盆地. 相似文献
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Orogeny, migmatites and leucogranites: A review 总被引:13,自引:0,他引:13
Michael Brown 《Journal of Earth System Science》2001,110(4):313-336
The type ofP-T-t path and availability of fluid (H2O-rich metamorphic volatile phase or melt) are important variables in metamorphism. Collisional orogens are characterized
by clockwiseP-T evolution, which means that in the core, where temperatures exceed the wet solidus for common crustal rocks, melt may be
present throughout a significant portion of the evolution. Field observations of eroded orogens show that lower crust is migmatitic,
and geophysical observations have been interpreted to suggest the presence of melt in active orogens. A consequence of these
results is that orogenic collapse in mature orogens may be controlled by a partially-molten layer that decouples weak crust
from subducting lithosphere, and such a weak layer may enable exhumation of deeply buried crust. Migmatites provide a record
of melt segregation in partially molten crustal materials and syn-anatectic deformation under natural conditions. Grain boundary
flow and intra-and inter-grain fracture flow are the principal grain scale melt flow mechanisms. Field observations of migmatites
in ancient orogens show that leucosomes occur oriented in the metamorphic fabrics or are located in dilational sites. These
observations are interpreted to suggest that melt segregation and extraction are syntectonic processes, and that melt migration
pathways commonly relate to rock fabrics and structures. Thus, leucosomes in depleted migmatites record the remnant permeability
network, but evolution of permeability networks and amplification of anomalies are poorly understood. Deformation of partially
molten rocks is accommodated by melt-enhanced granular flow, and volumetric strain is accommodated by melt loss. Melt segregation
and extraction may be cyclic or continuous, depending on the level of applied differential stress and rate of melt pressure
buildup. During clockwiseP-T evolution, H2O is transferred from protolith to melt as rocks cross dehydration melting reactions, and H2O may be evolved above the solidus at lowP by crossing supra-solidus decompression-dehydration reactions if micas are still present in the depleted protolith. H2O dissolved in melt is transported through the crust to be exsolved on crystallization. This recycled H2O may promote wet melting at supra-solidus conditions and retrogression at subsolidus conditions. The common growth of ‘late’
muscovite over sillimanite in migmatite may be the result of this process, and influx of exogenous H2O may not be necessary. However, in general, metasomatism in the evolution of the crust remains a contentious issue. Processes
in the lower-most crust may be inferred from studies of xenolith suites brought to the surface in lavas. Based on geochemical
data, we can use statistical methods and modeling to evaluate whether migmatites are sources or feeder zones for granites,
or simply segregated melt that was stagnant in residue, and to compare xenoliths of inferred lower crust with exposed deep
crust. Upper-crustal granites are a necessary complement to melt-depleted granulites common in the lower crust, but the role
of mafic magma in crustal melting remains uncertain. Plutons occur at various depths above and below the brittle-to-viscous
transition in the crust and have a variety of 3-D shapes that may vary systematically with depth. The switch from ascent to
emplacement may be caused by amplification of instabilities within (permeability, magma flow rate) or surrounding (strength
or state of stress) the ascent column, or by the ascending magma intersecting some discontinuity in the crust that enables
horizontal magma emplacement followed by thickening during pluton inflation. Feedback relations between rates of pluton filling,
magma ascent and melt extraction maintain compatibility among these processes. 相似文献
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南岭成矿带是太平洋及印度洋板块对中国大陆板块联合作用的结果。囊括大量稀有-有色金属矿床的中心弧形构造-岩浆岩系正是这个“钳式”应力场作用的集中体现,“深部叠加-重熔”——以板块持续运动和相对高速率运动产生并贮集能量为前提,以俯冲板块不断带入新的挥发物质为条件,随着动力热和挥发组分的不断回流—汇集—贮集而使仰冲板块深部预热的原地或途中固化-半固化的先期熔融的岩浆岩发生了二次甚至多次的熔融作用。 相似文献
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储层超压流体系统的成因机制述评 总被引:10,自引:2,他引:10
储层超压流体系统的基本要素包括压力封闭层、超压流体、岩石骨架和输导通道;由于储层超压系统所处环境的差异,其超压强度可以大于、等于和小于环境的超压强度;超压传递、不均衡压实、裂解气的生成和浮力作用是储层超压形成的重要机制;大多数储层超压是油气聚集的结果;超压释放是超压流体系统内部油气成藏的必要条件,研究储层超压流体系统将更直接地揭示超压盆地中油气运移和聚集的过程。 相似文献