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1.
内蒙古大青山一带早元古宙钾长花岗岩系的深熔成因及其构造环境 总被引：3，自引：0，他引：3
内蒙古大青山一带钾长花岗岩系同早元古宙再造岩系密切相伴生，其地质学、岩石学和地球化学特征表明，该区早元古宙时陆－陆碰撞挤压－逆冲作用引发陆壳物质的变质－溶熔作用，生成钾长花岗质岩浆，经固结先后生成了黑云母二长花岗岩－正长花岗岩－碱长花岗岩系列岩石。因其经受了由北向南的挤压－逆冲作用，也就构成了东西向的钾长花岗岩带。 相似文献
2.
本区经历四期变质作用,太古宙上壳岩系麻粒岩相变质、晚太古宙英云闪长岩高角闪岩相变质、早元古宙紫苏花岗岩类低角闪岩相变质和元古宙绿片岩相变质。麻粒岩相变质期可分三个阶段,早期角闪岩相、峰期麻粒岩相和晚期角闪岩相,其P-T-t轨迹为逆时针,与IBC型轨迹相似。导致麻粒岩相变质作用的热源为英云闪长质岩浆的垫托作用,形成于岛弧或活动大陆边缘。区内广泛发育的钾长花岗岩与晚太古宙高角闪岩相变质作用晚期的深熔作用有关。 相似文献
3.
胶东东部地区元古宙花岗岩类的地球化学及岩石成因 总被引：4，自引：3，他引：4
胶东东部地区的元古宙花岗岩－片麻岩杂岩，可分为：（１）石英闪长质－英云闪长质－花岗闪长质片麻岩、（２）二长花岗质－钾长花岗质片麻岩和（３）淡色花岗岩三套岩石。它们之间可识别侵位先后关系，岩相中普遍存在残留的斜长石板状晶体、并具环带结构为主的原生深成岩的矿物相组构，地球化学成分演化各具独立性，并具有深熔花岗岩的性质，结合同位素年龄资料，确立它们是元古宙不同造山阶段形成的花岗岩。岩石中普遍存在Ｔｉ、Ｙ、Ｓｒ、Ｎｉ及Ｍｇ等元素的强烈亏损，表明岩浆来源并非直接来源于上地幔或下地壳，它们是元古宙不同阶段已形成的岩石发生深熔作用形成的。这一认识有助于了解华北地台南缘东段元古宙这一重要地质时期的地壳形成和演化。 相似文献
4.
新元古代江南造山带远离晚中生代活动大陆边缘,是研究华南地区新元古代至早中生代多期造山作用的理想对象。文章通过对江南造山带东段沉积建造、岩浆活动、构造变形以及同位素年代学数据的综合分析,总结了其晋宁期、广西期以及印支期造山作用的特征。江南造山带东段在晋宁期经历了南北两侧大洋俯冲和两期碰撞造山作用。新元古代早期(880~860 Ma)双溪坞岛弧与扬子陆块东南缘发生弧-陆碰撞作用,形成淡色花岗岩、高压蓝片岩、NNE向褶皱-逆冲构造以及弧后前陆盆地。新元古代中期(约850 Ma),扬子陆块北缘开始发育由北向南的大洋俯冲。随着俯冲作用的进行,弧后盆地发生关闭,扬子陆块与华夏陆块发生陆-陆碰撞并形成新元古代(820~810Ma)江南造山带,导致近E-W走向褶皱-逆冲构造、韧性变形以及过铝质花岗岩的发育。江南造山带东段在约810Ma开始发生后造山垮塌和裂谷作用,以发育南华纪早期(805~750 Ma)花岗岩、中酸性火山岩、基性岩以及裂谷盆地为特征。江南造山带东段万载—南昌—景德镇—歙县断裂带以南地区卷入了华南广西期造山作用,发育近E-W走向由南向北的逆冲构造(465~450 Ma)、NNE向正花状构造(449~430 Ma)以及后造山近E-W走向韧性走滑剪切带(429~380 Ma)。印支期造山作用导致了NNE向褶皱-逆冲构造和花岗岩的发育,并奠定了江南造山带东段的基本构造面貌。 相似文献
5.
吉南大荒沟—板石沟地区早前寒武纪变质变形作用及地壳演化 总被引：3，自引：0，他引：3
本区早前寒武纪地壳曾经历了三期区域变质和变形作用：中太古宙最早期是上壳岩系沉积的形成，后来在２．６０５Ｇａ时发生角闪岩相区域变质作用，至晚期是英云闪长岩的侵位，并伴生有韧性剪切变形；晚太古宙时期，上壳岩系和英云闪长岩于２．５３８Ｇａ前后发生低角闪岩相变质，在晚期出现ＮＥ向韧性剪切变形事件；至早元古宙时期，早期是黑云钾长花岗岩侵入活动，大约在２．３８０Ｇａ时发育了绿片岩相变质，并发生二次浅层次的ＮＷ 相似文献
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研究表明，龙门山冲断带是川西前陆盆地的主要物源区，它的逆冲推覆活动直接控制着川西前陆盆地的沉积类型和沉积物供给量，晚三叠世诺利期，瑞替期和晚侏罗世早中期是川西前陆盆地构造沉降速率较高时期，反映龙门山冲断带在这些时期的逆冲推覆速率较大，是逆冲推覆作用构造抬升的强烈时期；而早侏罗世是该地区构造沉降时，估算龙门山逆冲推覆体在各个不同时期的抬升高度和抬升速率。 相似文献
8.
松－甘孜造山带东缘大小沟逆冲－滑脱岩片的边界断裂为韧性剪切带,具逆冲－推覆性质,在中生代碰撞造山过程中逆冲叠置于扬子陆块之上。岩片经历了晚二叠世裂谷变质,晚三叠世末至早中侏罗世滑脱－收缩动热变质和侏罗世热隆接触变质和晚侏罗世热隆接触变质３期变质形作用,尤其是后二者影响深刻,奠定了璀热隆构造,并瘵有碲矿床的形成。 相似文献
9.
阴山中生代地壳逆冲推覆与伸展变形作用 总被引：13，自引：2，他引：13
研究区属燕山－阴山中生代板内造山带西段的重要组成部分。依据变形特征和物质组成，可以分为北部构造活动带、中部隆起带和南部构造活动3个不同的构造区。以中部隆起带为中心，在南北两侧的构造活动带中的构造样式和变形机制呈反向对称出现。逆冲构造和伸展构造在时间和空间上的密切共生。在印支期－燕山早期地壳以逆冲挤压变形机制为主，形成了色尔腾山逆冲推覆体系和大青山逆冲推覆体系，而燕山晚期阶段在逆冲岩席上产生了背向伸展变形作用，形成了同构造的早白垩世呼和浩特－包头盆地和固阳盆地。 相似文献
10.
三江地区义敦岛弧碰撞造山过程：花岗岩记录 总被引：43，自引：5，他引：43
义敦岛弧碰撞造山带是特提斯－喜马拉雅巨型造山带中的一个复合造山带。本文利用义敦岛弧碰撞造山带29个花岗岩体的43件同位素测年数据，结合岩石地球化学特征，建立了造山带花岗岩的时间坐标。初步识别出4套不同成因类型的花岗岩，即印支期弧花岗岩、燕山早期同碰撞花岗岩、燕山晚期A型花岗岩和喜马拉雅期花岗岩。据此，再造了造山带的形成过程与演化历史：印支期的大规模俯冲造山作用（238－210Ma)，形成义敦火山岩浆弧；大约自206Ma始，发生弧－陆碰撞，伴随岛弧地壳挤压收缩和剪切变形，发育同碰撞花岗岩；进入燕山晚期（138－73Ma)，岛弧碰撞造山带发生造山后伸展作用，形成A型花岗岩带；喜马拉雅期发生陆内造山作用（65－15Ma)，岛弧碰撞造山带出现逆冲－推覆和大规模走滑平移，伴随喜马拉雅期花岗岩的侵位和拉分盆地的形成。 相似文献
11.
Partial melting has been shown to be an important mechanism for intracrustal differentiation and granite petrogenesis. However, a series of compositional differences between granitic melt from experiments and natural granites indicate that the processes of crustal differentiation are complex. To shed light on factors that control the processes of crustal differentiation, and then the compositions of granitic magma, a combined study of petrology and geochemistry was carried out for granites (in the forms of granitic veins and parautochthonous granite) from a granulite terrane in the Tongbai orogen, China. These granites are characterized by high SiO2 (>72 wt%) and low FeO and MgO (<4 wt%) with low Na2O/K2O ratios (<0.7). Minerals in these granites show variable microstructures and compositions. Phase equilibrium modelling using P–T pseudosections shows that neither anatectic melts nor fractionated melts match the compositions of the target granites, challenging the conventional paradigm that granites are the crystallized product of pure granitic melts. Based on the microstructural features of minerals in the granites, and a comparison of their compositions with crystallized minerals from anatectic melts and minerals in granulites, the minerals in these granitoids are considered to have three origins. The first is entrained garnets, which show comparable compositions with those in host granulites. The second is early crystallized mineral from melts, which include large plagioclase and K-feldspar (with high Ca contents) crystals as well as a part of biotite whose compositions can be reproduced by crystallization of the anatectic melts. The compositions of other minerals such as small grained plagioclase, K-feldspar and anorthoclase in the granites with low Ca contents are not well reconstructed, so they are considered as the third origin of crystallized products of fractionated melts. The results of mass balance calculation show that the compositions of these granites can be produced by mixing between different proportions of crystallized minerals and fractionated melts with variable amounts of entrained minerals. However, the calculated modal proportions of different crystallized minerals (plagioclase, K-feldspar, biotite and quartz) in the granites are significantly different from those predicted by melt crystallization modelling. Specifically, some rocks have lower modes of biotite and plagioclase, whereas others show lower K-feldspar modes than those produced by melt crystallization. This indicates that the crystallized minerals would be differentially separated from the primary magmas to form the evolved magmas that produce these granites. Therefore, the crystal entrainment and differential melt-crystal separation make important contributions to the composition of the target granites. Compared with leucogranites worldwide, the target granites show comparable compositions. As such, the leucogranites may form through the crystal fractionation of primary granitic magmas at different extents in addition to variable degrees of partial melting. 相似文献
12.
南天山英买来花岗岩的地质、地球化学特征及其地质意义 总被引：4，自引：0，他引：4
新疆英买来岩体位于南天山中段, 其主体由黑云母钾长花岗岩组成, 局部有二云母钾长花岗岩, 形成于晚二叠世.岩体中有两种少量椭球状的包体, 一是暗色细粒包体, 二是浅色包体.花岗岩和包体的地球化学特征基本相似, 它们在主量元素特征上以高Si、富K、富碱, 贫Mg、Ca为特征, 微量元素特征上表现为富Rb、Ba、Th以及轻重稀土的高度分馏和Nb、Ta、Zr、Hf等的负异常.花岗岩和包体的Harker图解显示出一致的变化趋势, 表明它们是同源岩浆演化的产物.其A/CNK值为0.99~1.08, 显示出准铝-过铝的特点, 而稀土元素配分曲线则显示出强烈富集轻稀土和明显的负Eu异常.结合其高的(87Sr/86Sr)t值(0.71036~0.71585)和负的εNd(t)值(-1.67~-6.45), 推测岩浆起源于壳源含斜长石的角闪石质岩石脱水条件下的部分熔融(深度＜50km), 其母岩浆在就位前发生了以黑云母和斜长石为主伴随有磁铁矿等副矿物的分离结晶作用.英买来花岗岩体的岩石类型以及地球化学特征表明其是介于A型和S型之间的一种过渡类型花岗岩类, 其形成时的构造环境为碰撞晚期或接近碰撞结束向后碰撞过渡阶段. 相似文献
13.
《International Geology Review》2012,54(8):695-710
Magmatism in central Anatolia is characterized by petrographically and chemically distinct granitic and syenitic rocks. The granitic magmatism comprises C-type (crustal-derived) and H-type (hybrid) monzogranites and monzonites. Garnet-bearing C-type leucogranites represent the oldest magmatic phase, but younger hornblende ± biotite ± K-feldspar H-type plutons dominate the geology of the Central Anatolian Crystalline Complex (CACC). These typically include mafic microgranular enclaves. The granitic magmatism predates syenitic intrusions, among which quartz-bearing syenites were emplaced prior to feldspathoid-bearing ones. The nature of magmatism in central Anatolia varies through time from peraluminous to metaluminous to alkaline. These different magma types reflect distinct stages of postcollisional magmatism, in which interaction between crust and mantle varied considerably. The C-type granites of the early stages of postcollisional magmatism were likely derived by partial melting of the lower continental crust induced by mafic magma underplating as a result of lithospheric delamination. The H-type granites and syenites of the mature and advanced stages of postcollisional magmatism indicate a significant contribution from mande-derived magma within a continuous or episodic extensional tectonic regime. 相似文献
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华南富锂氟含稀有金属花岗岩的成冈分析 总被引：3，自引：0，他引：3
雪球结构的产出特征、钠长石电子探针分析及其它间接证据都说明,雪球结构是在岩浆结晶过程中形成的。雪球结构形成与否主要与岩浆熔体中Ｎａ２Ｏ／Ｋ２Ｏ比值和Ｆ、Ｈ２Ｏ含量有关。较大的Ｎａ２Ｏ／Ｋ２Ｏ比值（〉１）例钠长石首先从熔体中晶出;较高的Ｆ含量使岩浆固相线温度大大降低,有利于岩浆分异演化并形成接近端员组分的钠长石和钾长石同的Ｈ２Ｏ含量有利于石英以较快的速度生长并逐渐包裹钠长石形成雪球结构。自形的α－石英斑晶、接近各自端员组分的甲和工石和钠长石等说明该类花岗岩形成温度较低,众多的地质、地球化学依据都证明了,华南富锂氟含稀有金属花岗岩是从过铝富氟富钠的残余熔体中直接结晶而成的。 相似文献
16.
K-feldspar crystals >5 cm in greatest dimension are common in calc-alkaline granites and granodiorites worldwide. Such megacrysts are generally interpreted as having grown to large sizes early in a magma’s crystallization history while they were largely molten, owing to field relations such as megacryst alignment and megacryst-rich clusters and to crystallographic features such as zonally arranged inclusions and sawtooth Ba zoning. These features are consistent with early growth but do not require it. In contrast, experimental petrology, mineral compositions, and natural examples of partial melting of granite demonstrate that K-feldspar is typically the last major phase to crystallize and that most K-feldspar growth occurs after the magma crosses the rheologic lock-up threshold of ~50 % crystals. The near-absence of K-feldspar phenocrysts in dacite lavas and tuffs, even in highly crystalline ones, demonstrates that natural magmas do not precipitate significant K-feldspar while they are mobile. The highly potassic compositions of megacrysts (and indeed, of K-feldspar in non-megacrystic granites as well) require exsolution of albite component down to temperatures of ~400 °C. The low Ca contents of megacrysts cannot result from exsolution of anorthite and must represent recrystallization of the crystals at low temperature. These mineralogical and experimental constraints require that K-feldspar megacrysts indicate widespread and thorough recrystallization of the host granites and granodiorites. 相似文献
17.
Miroslav Štemprok David Dolejš Axel Müller Reimar Seltmann 《Contributions to Mineralogy and Petrology》2008,155(1):93-109
We report new occurrences of “two-phase” granitic textures from the Western Krušné hory/Erzgebirge pluton (central Europe)
and use crystal-size distribution data and thermodynamic modeling to interpret their crystallization conditions. The two-phase
texture consists of (1) early phenocrysts of quartz, plagioclase, K-feldspar and biotite, (2) medium-grained matrix of the
same phases and (3) interstitial channels and patches of a late-stage, very fine-grained matrix. The porphyritic two-mica
microgranites, which host two-phase textures, occur as minor intrusions in early low-F biotite granites or as marginal parts
of evolved high-F Li-mica granites. Measurements of the crystal-size distribution of quartz revealed three grain populations:
(1) early phenocrysts (0.5–3.0 mm) showing partial resorption by residual melt, (2) a medium-grained population of the equigranular
rock matrix (0.05–0.50 mm) that experienced minor coarsening by subsolidus annealing and (3) a fine-grained population (<0.03 mm)
in the interstitial channels and patches formed during rapid devolatilization; this quartz group shows no or poor grain coarsening.
All samples exhibit similar fraction of the fine-grained population (44–52%) but proportions of phenocrysts to medium-grained
matrix vary significantly. Thermodynamic modeling of liquidus equilibria and experimental data in the hydrous haplogranite
system require: (1) ascent of a granitic suspension (15–25% phenocrysts) under H2O-undersaturated conditions at 25–45 bar/°C and a cooling rate of 40 J/(g kbar) in order to produce partial resorption of
quartz phenocrysts and continued growth of feldspar phenocrysts, followed by (2) emplacement as discrete intrusions or bodies
along pluton roof accompanied by sudden devolatilization. At the onset of matrix nucleation, disequilibrium undercooling of
70–85°C was inferred from the presence of micrographic intergrowths of quartz and K-feldspar. The two-phase granites in the
Western Krušné hory/Erzgebirge pluton and in the Southeast Asian batholith form compositionally narrow groups with high-silica
and moderate volatile enrichments but they differ in peraluminosity and phosphorus concentrations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Granitic rocks of various ages and composition are found in the Schwarzwald region of West Germany. These granites range in age from Upper Devonian to Upper Carboniferous (370-280 m.y.) and in composition from granodiorites to alkali feldspar granites. 14 representative samples of twelve different types were analysed for their La, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Lu by instrumental neutron activation. The studies reveal that there are characteristic differences between the different types of granitic rocks both as regards to their total REE content as well as the distribution pattern of these elements. These differences can not be directly related to the variations in the major element chemistry or the mineralogy of the granites. On the other hand, a relationship is found between the age of the granitic rocks and the total REE as well as their distribution pattern. In general the ΣREE varies from 22 to 215 ppm in different types. The ΣLa-Lu increases gradually in the direction Upper Devonian→Lower Carboniferous, however, in the granitic rocks of the Upper Carboniferous this trend is reversed and there is again a marked depletion in the content of REE. The chondrite normalised patterns of all the older types give a smooth concave curve with decrease of concentration from La to Lu. All the Upper Carboniferous granites on the other hand are characterised by a progressive pronounced negative Eu anomaly. The gradual increase of the ΣREE in the older granites is related to their evolution by progressive anatexis, whereas, the decrease in the total REE content in case of the younger Upper Carboniferous granites is due to processes of magmatic differentiation. The depletion of Eu in these K-feldspar rich types of granite is probably related to the breakdown of biotite in the anatectic starting material. 相似文献
19.
月球花岗岩--比较行星学意义 总被引：1，自引：1，他引：0
与大陆地壳广泛出露的花岗岩不同,在月球表面仅发现了少量细小的花岗岩碎屑,此外有长英质组分以熔体包裹体形式出现于月球玄武岩的矿物中。月球花岗岩碎屑的主要矿物为石英、钾长石和钙质斜长石,具花斑状结构;含少量铁橄榄石、单斜辉石、钛铁矿、锆石、磷灰石、白磷钙矿等矿物,缺少含水矿物。月球花岗岩富K2O,富Ba,相容元素(Cr、Sc、Co、V)含量比其它月岩低,具有平坦或Ⅴ型的REE型式,负Eu异常明显。它们的化学特征可以用硅酸盐液态不混熔来解释。月球花岗岩的结晶年龄在4．4～3．9Ga间,具有至少8个年龄峰,可能代表了与花岗岩形成相关的8次独立的岩浆事件。由于月球花岗岩成因和分布对于认识月球演化和岩浆作用历史至关重要,在新一轮的深空探测中,应更加重视对月球花岗岩的研究。 相似文献
20.
The late Paleozoic to early Mesozoic granites exposed in northwestern Lao PDR provide important constraints on the tectonic evolution of the Eastern Paleotethyan Ocean and regional correlation with the giant granitic belt in Southeast Asia. New geochronological data show that the granites have Late Triassic zircon U–Pb ages of 231–220 Ma. They are dominated by monzogranite and biotite granite with an I-type geochemical affinity. These granites are enriched in LREEs and LILEs and depleted in HFSEs. The geochemical variations for these granites indicate the fractional crystallization of plagioclase, K-feldspar, biotite, apatite, and Fe–Ti oxides. Their initial 87Sr/86Sr ratios range from 0.7021 to 0.7105 and εNd (t) values from −1.6 to −7.3. Zircon in-situ εHf (t) values are in range of −6.0–+5.3 (peaks at −2.8 and +2.5, respectively), Hf model ages of 0.67–1.64 Ga (peaks at 0.83 Ga and 1.45 Ga, respectively), and δ18O values of 6.6‰–8.0‰, similar to the Late Triassic granitoids from the Eastern Province in Southeast Asia. These granites originated from a mixed source of ancient metamorphic rocks with juvenile mafic crust. The Late Triassic granites in northwestern Lao PDR formed in a post-collisional setting in response to the thickened crustal collapse during the assembly of the Sibumasu with Indochina blocks. These granites can southerly link with the Eastern granite province of the Eastern Paleotethyan Domain in Southeast Asia. 相似文献