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1.
萨勒巴斯推覆体中发育一套深层次变形构造组合和倒转递增变质带,其中糜棱岩、混合岩、混合花岗岩的成因关系对研究挤压造山背景下,地壳深层次变形作用和成岩作用具有特殊的意义。研究表明:在大型滑脱推覆系统中,存在糜棱岩—混合岩—混合花岗岩成岩系列;成岩过程为:韧性变形—剪切加热—部分熔融;控制成岩过程的主导因素为构造动力条件。这一成岩过程能导致稀土元素发生分异,出现重稀土元素有规律地亏损,变质作用pTt轨迹显示造山过程中逆冲推覆作用导致的地壳叠置加厚和剪切加热的典型热演化模式,变形、变质高峰期后,高角度逆冲作用导致变形岩石经历减压、降温的退变质作用,形成由南向北的倒转递增变质带。 相似文献
2.
喜马拉雅碰撞造山带新生代地壳深熔作用与淡色花岗岩 总被引：12，自引：10，他引：2
自从印度-欧亚大陆碰撞以来,伴随着构造演化和温度-压力-成分(P-T-X)的变化,喜马拉雅造山带中下地壳变质岩发生不同类型的部分熔融反应,形成性质各异的过铝质花岗岩。这些花岗岩在形成时代、矿物组成、全岩元素和放射性同位素地球化学特征上都表现出巨大的差异性。始新世构造岩浆作用形成高Sr/Y二云母花岗岩和演化程度较高的淡色花岗岩和淡色花岗玢岩,它们具有相似的Sr-Nd同位素组成,是碰撞早期增厚下地壳部分熔融的产物。渐新世淡色花岗岩主要为演化程度较高的淡色花岗岩,可能指示了喜马拉雅造山带的快速剥露作用起始于渐新世。早中新世以来的淡色花岗岩是喜马拉雅造山带淡色花岗岩的主体,是变泥质岩部分熔融的产物,包含两类部分熔融作用——水致白云母部分熔融作用(A类)和白云母脱水熔融作用(B类)。这两类部分熔融作用形成的花岗质熔体在元素和同位素地球化学特征上都表现出明显的差异性,主要受控于两类部分熔融作用过程中主要造岩矿物和副矿物的溶解行为。这些不同期次的地壳深熔作用都伴随着高分异淡色花岗岩,伴随着关键金属元素(Nb、Ta、Sn、Be等)的富集,是未来矿产勘探的重要靶区。新的观测结果表明:在碰撞造山带中,花岗岩岩石学和地球化学性质的变化是深部地壳物质对构造过程响应的结果,是深入理解碰撞造山带深部地壳物理和化学行为的重要岩石探针。 相似文献
3.
五台山早前寒武纪碰撞造山带中的韧性剪切带及其大地构造… 总被引：1，自引：0，他引：1
在五台山早前寒武纪碰撞造山带中存在的两种类型韧性剪切带，即逆冲型和伸展型剪切带。除变质程度不同外，南部和北部构造片体中的角闪岩相逆冲型韧性剪切带与中部构造片体中的绿片岩相逆冲型韧性剪切带具有相同的变形特征，它们形成于同一变形过程，是造山作用早期地壳拼合阶段的产物。伸展型韧性剪切带在整个造山带都有分布，与造山作用晚期显著增厚的地壳发生大规模纵向伸展作用相联系。 相似文献
4.
在五台山早前寒武纪碰撞造山带中存在两种类型韧性剪切带，即逆冲型和伸展型剪切带。除变质程度不同外，南部和北部构造片体中的角闪岩相逆冲型韧性剪切带与中部构造片体中的绿片岩相逆冲型韧性剪切带具有相同的变形特征，它们形成于同一变形过程中，是造山作用早期地壳拼合阶段的产物。伸展型韧性剪切带在整个造山带都有分布，与造山作用晚期显著增厚的地壳发生大规模纵向伸展作用相联系 相似文献
5.
北秦岭新元古代后碰撞花岗岩的确定及其构造意义 总被引：42，自引：0，他引：42
应用LA ICPMS获得北秦岭蔡凹花岗岩体锆石U Pb年龄 ( 889± 1 0 )Ma ,代表岩体的形成时代。该岩体富集LILE、贫化HFSE ,显示活动陆缘俯冲带I型花岗岩体地球化学特征。同时岩体又具有富铝、高钾和锶、明显亏损Nb、Ti、P等元素的大陆造山带后碰撞演化阶段花岗岩特征。根据区域构造资料并结合岩体的变形特征分析 ,蔡凹岩体为碰撞造山过程地壳增厚背景下 ,在后碰撞拉张阶段由卷入有消减带物质的下部地壳部分熔融所形成 ,指示了秦岭在该时期已进入由主碰撞挤压转向后碰撞伸展演化阶段 ,为进一步精细确定北秦岭新元古代陆块汇聚碰撞造山过程提供了新的依据 相似文献
6.
山东沂水紫苏花岗岩中残晶相矿物的发现及紫苏花岗岩的形成过程 总被引：4，自引：0，他引：4
山东沂水地区紫苏花岗岩主要有 3种类型 ,分别为紫苏花岗闪长岩、紫苏石榴花岗闪长岩和紫苏奥长花岗岩。紫苏花岗岩中普遍存在有熔体交代结构 ,主要由残晶相矿物和结晶相矿物组成。对紫苏花岗岩及变质表壳中流体包裹体产状、成分的研究发现 ,富CO2 流体包裹体和富N2 流体包裹体均来自地幔深部。紫苏花岗岩的形成过程如下 :基性岩浆的底侵作用使本区经历了第一期麻粒岩相变质作用 ,地幔富CO2 流体包裹体的存在使系统a(H2 O)很低 (a(H2 O) =0 .1～ 0 .3) ,麻粒岩相变质作用没有产生熔融作用。幔源岩浆活动的逐渐停止 ,该区又经历了近等压降温的第二期麻粒岩相变质作用。此时 ,深源富CO2 流体作用减弱 ,水的活度增加 ,a(H2 O) =0 .6 5～ 0 .75 ,从而产生岩浆 ,新生岩浆对早期形成的变质矿物进行熔蚀交代作用 ,使早期形成的难熔变质矿物如紫苏辉石、石榴石、单斜辉石等呈残晶相 ,随着温度的降低岩浆基本在原地半原地结晶形成紫苏花岗岩。 相似文献
7.
腾冲地块高地热异常区晚白垩世-始新世钾玄质强过铝花岗岩岩石地球化学、年代学特征及构造意义 总被引：3，自引：2，他引：1
腾冲地块高地热异常区清水左所营初糜棱岩化黑云母二长花岗岩岩体、新华黑石河热田强糜棱岩化黑云母二长花岗岩岩体、热海热田硫磺塘硅化碎裂正长花岗岩岩体变形变质、岩石地球化学及锆石年代学的研究表明,晚白垩世(73Ma)初糜棱岩化黑云母二长花岗岩岩体为高温钾玄质强过铝花岗岩,形成于活动大陆边缘火山弧-后碰撞转换或过渡构造环境,并经历强烈伸展变形作用,普遍发育早期近水平-低角度(30°)韧性伸展剪切糜棱面理,局部发育晚期高角度右旋走滑挤压韧性糜棱面理;始新世(48~46Ma)强糜棱岩化黑云母二长花岗岩岩体、硅化碎裂正长花岗岩岩体为中-高温钾玄质强过铝花岗岩,并具铝质A型花岗岩特征,形成于后碰撞-板内构造环境,以发育晚期高角度(70°~87°)右旋走滑挤压韧性糜棱面理为特征,其右旋走滑韧性剪切变形时代晚于始新世(48~46Ma)。晚白垩世-始新世钾玄质强过铝花岗岩的形成与俯冲-碰撞造山隆升后的伸展垮塌、拆沉地幔物质上涌玄武质岩浆底侵和地壳部分熔融作用密切相关。始新世-第四纪岩浆活动与高地热异常区(带)空间上密切伴生,新近纪晚期-第四纪构造活动主要表现为脆性走滑-拉张正断层和构造拉分断陷盆地的形成,构造断陷边界断裂与深部岩浆活动是导致腾冲地区高地热异常区(带)中-高温地热温泉沿走滑-拉张断裂带集中分布的主要原因。 相似文献
8.
胶东矿集区大规模成矿时间和构造环境 总被引：41，自引：22，他引：41
本文全面收集了胶东矿集区矿床和相关岩石的同位素年龄,讨论了该区金矿床大规模成矿的时间和构造背景.数据显示成矿作用发生于中生代,以110～130Ma为高峰;成矿事件同步或略滞后于中生代花岗岩浆活动.铷锶和锆石SHRIMP年龄表明中生代花岗岩类形成于多次热事件,大量继承锆石的存在和较高的ISr值(＞0.709)指示花岗岩浆主要源于地壳物质的部分熔融或重熔.矿石和成矿流体的Isr值普遍高于0.709,并略高于中生代花岗岩类,指示成矿流体和物质主要来自地壳内部.讨论显示,中生代华北与华南古板块的碰撞造山作用是导致胶东矿集区形成的主导因素;花岗岩类侵入和大规模成矿作用耦合于碰撞造山带的3阶段地球动力学演化,即早阶段挤压-地壳缩短-隆升,中阶段岩石圈拆沉并转向伸展构造体制,晚阶段伸展;最强烈的成矿作用发生在碰撞造山过程的挤压向伸展转变期;已建立的碰撞造山成岩成矿和流体作用模式可以较好解释胶东矿集区的矿床、花岗岩类的特征. 相似文献
9.
陕川丁家林-太阳坪-董家院金矿带的矿田构造-岩相学研究 总被引：1，自引：0，他引：1
陕西丁家林-四川太阳坪-四川董家院北东向金矿带位于后龙门山陆内造山带,构造动力学背景为陆-陆板块碰撞而形成的逆冲推覆造山带,金矿带内发育一系列与陆内造山作用密切有关的北东向递进脆-韧性剪切带。本文以构造-岩相学新方法为指导,在矿田构造-岩相学层次上,通过实测构造-岩相学剖面和岩石地球化学研究,对该金矿带物质学和运动学特征研究表明,赋矿地层志留系黄坪组(S1-2hn)区域性岩相学特征整体为陆棚相。黄坪组中部层间流体活动强烈,地壳浅部富Fe-Mg-CO32–型构造流体活动形成了斑点状铁碳酸盐千枚岩相;随构造变形层次加深,强应变带发育构造片岩相和初糜棱岩相,富Si O2型流体排泄的构造分异成岩作用形成了流变状糜棱岩相。强烈的构造成岩作用及造山带流体的大规模排泄形成了糜棱岩相,同位发育密集的流变状糜棱岩相和蚀变菱铁矿铁白云石网脉相。构造流体成岩成矿作用集中于强应变带形成蚀变糜棱岩相,后期脆性蚀变碎裂岩相叠加时,金矿化(体)发育。早期韧性剪切和脆韧性剪切变形并叠加有后期脆性变形构造,富集Au-Cu-Sb-W-Bi等元素组合。本区缺少或未见早三叠世以后形成的岩浆活动。大规模富Fe-Mg碳酸盐型流体及同构造期造山带流体活动与龙门山陆内造山带密切相关,表明丁家林-太阳坪-董家院金矿为造山型金矿。 相似文献
10.
碰撞造山作用过程中陆壳岩石熔融形成花岗岩浆主要出现在加热期和伸展抬升期，是碰撞后岩石圈热状态调整引起陆壳物质化学分异的结果。陆壳碰撞前的构造历史，大陆岩石圈的热参数和地幔过程，造山带的几何学特征和运动学性质等制约了造山带花岗岩类的发育，尤其是与各种造成地幔高热流叠加于下部地壳的岩石调整过程关系密切。 相似文献
11.
Charnockitic magmatism in southern India 总被引：2，自引：0，他引：2
Large charnockite massifs cover a substantial portion of the southern Indian granulite terrain. The older (late Archaean to
early Proterozoic) charnockites occur in the northern part and the younger (late Proterozoic) charnockites occur in the southern
part of this high-grade terrain. Among these, the older Biligirirangan hill, Shevroy hill and Nilgiri hill massifs are intermediate
charnockites, with Pallavaram massif consisting dominantly of felsic charnockites. The charnockite massifs from northern Kerala
and Cardamom hill show spatial association of intermediate and felsic charnockites, with the youngest Nagercoil massif consisting
of felsic charnockites. Their igneous parentage is evident from a combination of features including field relations, mineralogy,
petrography, thermobarometry, as well as distinct chemical features. The southern Indian charnockite massifs show similarity
with high-Ba-Sr granitoids, with the tonalitic intermediate charnockites showing similarity with high-Ba-Sr granitoids with
low K2O/Na2O ratios, and the felsic charnockites showing similarity with high-Ba-Sr granitoids with high K2O/Na2O ratios. A two-stage model is suggested for the formation of these charnockites. During the first stage there was a period
of basalt underplating, with the ponding of alkaline mafic magmas. Partial melting of this mafic lower crust formed the charnockitic
magmas. Here emplacement of basalt with low water content would lead to dehydration melting of the lower crust forming intermediate
charnockites. Conversely, emplacement of hydrous basalt would result in melting at higher {ie565-01} favoring production of
more siliceous felsic charnockites. This model is correlated with two crustal thickening phases in southern India, one related
to the accretion of the older crustal blocks on to the Archaean craton to the north and the other probably related to the
collision between crustal fragments of East and West Gondwana in a supercontinent framework. 相似文献
12.
The Neoarchean charnockites of North margain of North China Craton(NCC) has become a hot topic into understanding the Early Precambrian basement. Although there is a broad consensus that charnockite is usually related to granulite facies metamorphism, whether its petrogenesis and tectonics characteristics remains controversial. Inclusions within hypersthene and garnet in charnockite are used to identify the peak granulite facies mineral assemblage, with the formation of Magnesian–charnockite attributed to anatexis of the protolith associated with this granulite facies metamorphism. The distribution of major and trace elements in charnockite is very uneven, significant depleted in LILEs(eg. Cs, U, Th) and HFSEs(eg. Nb, Ta, P and Ti), riched in Sr. Raising to the coexistence of Eu–enrichment and Eu–depletion type of REE patterns that influenced by the content of plagioclase and the remnants minerals of zircon and apatite. Comparative the petrography, geochemistry and geochronology data of Magnesian–charnockite indicate that the ratios of mafic pellites and basalts involved in anatectic melting are different by the upwelling of mantle magma, also resulting in the Eu anormals characteristics. The formation of the Magnesian–charnockite is closely connected with the subduction of the NCC oceanic crust(About ～2.5 Ga). However, Ferroan–charnockite may be the formed by the crystallization differentiation of the upwelling of mantle–derived shoshonitic magma(About ～2.45 Ga), with the lower crust material addition. 相似文献
13.
14.
Rajib Kar 《Journal of Earth System Science》2001,110(4):337-350
The charnockite patches that occur within leptynite host, in and around Jenapore, northern sector of the Eastern Ghats granulite
belt, are disposed in a linear fashion and generally have sharp lithological contact with the host leptynite. Sometimes the
patches and foliations of the host are cofolded. Also, the patches sometimes have the internalS
1 foliation, while the host leptynite records onlyS2 foliation. Mineralogically and chemically patchy charnockites and host leptynites are distinct entities, and cannot be related
by any prograde and retrograde reactions. Particularly important is the peraluminous granitic composition and high Rb/Sr ratios
of the leptynites, presumably resulting from biotite-dehydration melting; as against metaluminous granodioritic to tonalitic
composition and low Rb/Sr ratios of the patchy charnockites, presumably resulting from hornblende-dehydration melting. The
charnockite patches here can be interpreted as caught up patches or xenolith within granitic melt (leptynite). Mg-rich rims
of garnet in the charnockite patch were probably caused by heat from the crystallising melt or decompression during ascent
of melt. 相似文献
15.
Reactions occurring during cooling of charnockitic intrusives on the Lofoten Islands produce characteristic diffusion-controlled textures around fayalite and Fe–Ti oxides. Thermobarometry indicates the corona textures formed at 780–840 °C and pressures of 4–10 kbar, whereas the magmatic assemblage of the charnockite (clinopyroxene–olivine–quartz) crystallized at about 850–870 °C and 4 kbar. The succession olivine|orthopyroxene+magnetite|orthopyroxene+garnet and olivine|orthopyroxene+magnetite|amphibole developed where olivine reacted with adjacent plagioclase or K-feldspar, but the modes and the thicknesses of the corona textures vary according to the feldspar type, indicating that the primary magmatic ternary feldspar was already exsolved into albitic plagioclase and alkali feldspar when the corona formation began. Simultaneously, in other parts of the rock, primary magmatic clinopyroxene reacted to amphibole and Fe–Ti oxides reacted to orthopyroxene+garnet coronas or to amphibole. Textures demonstrate significant Al diffusion in the rocks under granulite facies conditions and they suggest that no pervasive fluid influx occurred and that amphibole formation was dependant on a local source of H2O probably related to water-release during the last stages of magmatism. Calculation of the net reaction by accounting for all observed reactions at different sites in the rock indicates that the system can be regarded as balanced on a hand-specimen scale with respect to all elements except for Na and H2O. The larger variety of textures developed in rocks of granitic bulk composition provide more constraints than textures from gabbroic compositions, and permitted calculation of a set of relative diffusion coefficients which also reproduce textures in the gabbroic and anorthositic rocks from the Lofoten Islands. The following set of relative diffusion coefficients (Li/LFe) reproduces the observed textures in the Lofoten rocks: Si=0.82, Mg=0.59, Mn=0.05, Na=0.38, K=0.39, Al=0.05 and Ca=0.07. 相似文献
16.
17.
The late Archaean Closepet granite of southern India is bounded by N-S trending shear zone. At the southern end of the granite
both charnockite and granite veins are spatially associated with ductile shears. These shears continue further north and are
confined to the contact zones in the central part of the granite outcrop. The main component of the shear zone are highly
deformed granite sheets, augen gneisses and mylonites. Field observations and microstructural fabric of mylonites indicate
a dextral sense of shear movement. Field evidence suggests that shear deformation was active throughout the evolution of the
Closepet granite 相似文献
18.
Constraints on the timing and conditions of high‐grade metamorphism,charnockite formation and fluid–rock interaction in the Trivandrum Block,southern India 
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下载免费PDF全文 E. Blereau C. Clark R. J. M. Taylor T. E. Johnson I. C. W. Fitzsimons M. Santosh 《Journal of Metamorphic Geology》2016,34(6):527-549
Incipient charnockites have been widely used as evidence for the infiltration of CO2‐rich fluids driving dehydration of the lower crust. Rocks exposed at Kakkod quarry in the Trivandrum Block of southern India allow for a thorough investigation of the metamorphic evolution by preserving not only orthopyroxene‐bearing charnockite patches in a host garnet–biotite felsic gneiss, but also layers of garnet–sillimanite metapelite gneiss. Thermodynamic phase equilibria modelling of all three bulk compositions indicates consistent peak‐metamorphic conditions of 830–925 °C and 6–9 kbar with retrograde evolution involving suprasolidus decompression at high temperature. These models suggest that orthopyroxene was most likely stabilized close to the metamorphic peak as a result of small compositional heterogeneities in the host garnet–biotite gneiss. There is insufficient evidence to determine whether the heterogeneities were inherited from the protolith or introduced during syn‐metamorphic fluid flow. U–Pb geochronology of monazite and zircon from all three rock types constrains the peak of metamorphism and orthopyroxene growth to have occurred between the onset of high‐grade metamorphism at c. 590 Ma and the onset of melt crystallization at c. 540 Ma. The majority of metamorphic zircon growth occurred during protracted melt crystallization between c. 540 and 510 Ma. Melt crystallization was followed by the influx of aqueous, alkali‐rich fluids likely derived from melts crystallizing at depth. This late fluid flow led to retrogression of orthopyroxene, the observed outcrop pattern and to the textural and isotopic modification of monazite grains at c. 525–490 Ma. 相似文献
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华北克拉通北缘西部陆块早前寒武纪基底分布广泛,现有的研究普遍认为经历 2.5 Ga,2.45~2.37 Ga,1.95 Ga和1.85 Ga变质热事件影响。华北克拉通北缘阴山陆块中2.5 Ga的紫苏花岗岩研究已经成为了揭示华北克拉通北缘早前寒武纪构造演化的一个热点,但孔兹岩带中却鲜少有新太古代晚期构造热事件的相关报道。近年来,相继从大青山地区的孔兹岩带石榴黑云母片麻岩中分辨出一期具有2.45~2.37 Ga变质锆石年龄的大青山表壳岩,同时出露与其成因关系密切的深熔石榴花岗岩,但其深熔成因的模式存在争议。本文对大青山地区新发现的新太古代晚期紫苏花岗岩、石榴花岗岩及其围岩的野外空间产出关系和锆石年代学进行对比分析,为探究深熔石榴花岗岩成因模式提供重要的启示。 相似文献
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研究区内广泛出露的太古代岩石属于迁西群麻粒岩,包括麻粒岩、紫苏花岗岩、辉石-斜长片麻岩、角闪岩等。对这些岩石中辉石、角闪石、黑云母等矿物的研究结果表明,这些矿物具有明显的麻粒岩相成因特征,角闪石、黑云母同辉石等平衡共存。紫苏花岗岩中矿物除有序度增高外,其他特征与麻粒岩、片麻岩中的矿物相似。 根据矿物对地质温压计计算得到:本区第一期变质作用p-t条件为770-870℃,7.2-8.4k bar第二期为740-760℃,6.6-8.4k bar;矿物氧同位素温度为470-570℃,代表另一次程度较低的变质作用。 相似文献