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本文以藏南邛多江变质核杂岩中花岗岩类侵入岩体为研究对象,分别对仲格耐和倾日二长花岗岩环(株)中的新鲜黑云母样品进行了~(40)Ar/~(39)Ar 同位素年龄测定。仲格耐二长花岗岩环黑云母样品的坪年龄和等时年龄分别为(13.30±0.32)Ma 和(12.90±2.90)Ma,而倾日二长花岗岩株黑云母样品的坪年龄和等时年龄则为(12.35±0.14)Ma 和(12.37±0.26)Ma。与倾日岩株相比,仲格耐岩环黑云母样品的坪年龄值相对较高些,暗示了其相对较早的形成时间。考虑到倾日二长花岗岩株形成之后基本未遭受到明显构造-岩浆活动影响,因此,12Ma 也许代表了黑云母的结晶时间,属中喜马拉雅时期构造-岩浆活动的产物。确切地讲,邛多江变质核杂岩及有关花岗岩类侵入岩的形成时间不是老第三纪的渐新世,而是新第三纪的中新世。本区花岗岩类侵入岩形成时代的确定,对于探讨本区中酸性岩浆岩的形成过程和揭示藏南拆离构造体系的动力学机制均具有重要意义。 相似文献
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红石泉岩体地处北祁连造山带的龙首山成矿带西南缘,区内发育伟晶岩型铀矿床。本文对红石泉岩体进行岩相学、岩石地球化学研究,探讨其岩石成因、岩浆来源,厘定其构造环境。元素地球化学结果显示：岩体具中硅、富铝,富钠特征,为准铝质高钾碱性正长岩系列。在微量元素图解中,样品富集Rb、U、K、Nd等元素,亏损高场强元素Nb、Ta、Ti及元素P等;在稀土元素球粒陨石标准化图解中,样品富集轻稀土,轻重稀土分馏明显,Eu显示正异常。样品显示高的Zr+Nb+Ce+Y的值,属A型花岗岩。结合其元素地球化学特征及区域内岩浆岩的演化,厘定岩体为祁连板块与阿拉善板块碰撞后拉张环境下,壳源岩浆与幔源岩浆混合形成。 相似文献
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新疆准噶尔地区花岗岩中微粒闪长质包体特征及后碰撞花岗质岩浆起源和演化 总被引：20，自引：0，他引：20
新疆准噶尔地区也布山、庙儿沟两个晚古生代后碰撞准铝一过铝质花岗岩体中，广泛发育大量的暗色微粒闪长质包体。岩石学、矿物学、主量元素和微量元素地球化学研究表明，包体与其寄主岩存在明显的亲缘关系。东准噶尔也布山黑云母花岗岩体中的暗色微粒包体与寄主岩有相似的地球化学成分，表明它是与寄主花岗岩相同成因的同源包体，是来自上地幔的基性岩浆经过高度演化、结晶分异的产物；西准噶尔庙儿沟二长花岗岩体中含钾长石斑晶的微粒包体则主要是由幔源的下地壳基性岩部分熔融形成的残余体，被酸性岩浆携带并发生成分上的同化和混染，最后在上地壳侵位的产物。同准噶尔碱性花岗岩一样，载荷包体的准铝一过铝质花岗岩是晚古生代后碰撞阶段构造一岩浆活动的岩石类型之一，其形成和演化标志了准噶尔地区后碰撞幔源岩浆底侵作用导致大陆地壳垂向生长的过程。 相似文献
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碰撞后岩浆活动对于了解造山带垮塌和去根过程及陆壳生长具有重要意义.总结了柴北缘超高压变质带中形成于400～360 Ma的碰撞后花岗岩-辉长岩侵入体和镁铁质岩脉的年代学和地球化学特征.其中，花岗岩侵入体具有典型的I-型花岗岩特征，形成于壳幔相互作用的岩浆混合.来自地幔的镁铁质岩脉可以划分为两组：（1）392～375 Ma中基性岩脉；（2）约360Ma超基性岩脉.其地球化学特征表明，镁铁质岩脉的微量元素和同位素随形成时间的变新而逐渐亏损，地幔源区从岩石圈地幔变为软流圈地幔.这种源自地幔的镁铁质岩浆活动是碰撞后岩浆活动开始和造山带垮塌的关键指标.结合碰撞后岩浆作用的特征，提出了一个地球动力学模型来解释柴北缘约35百万年（Ma）的造山带垮塌去根过程，在395～375 Ma发生缓慢的岩石圈地幔侵蚀，360 Ma前岩石圈发生拆沉作用，岩石圈地幔垮塌，同时软流圈地幔上升.地幔岩浆的加入表明碰撞后阶段是大陆生长的重要时期. 相似文献
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崇山杂岩带为滇西三江造山系西侧边缘的一条重要边界构造,属青藏高原造山带的南东缘.带内岩浆活动强烈,前人认为其主要由晚元古代、中生代的花岗岩组成;而据地质调查发现,带内新生代的岩浆作用十分发育.本文对带内新发现的灰白色黑云二花岗岩进行研究,获得了锆石U-Pb LA-ICP-MS年龄为34.88 Ma和35.25 Ma,表明其侵位于古近纪始新世.岩石地球化学表明,黑云二花岗岩为钾玄质-高钾钙碱性系列的过铝质花岗岩类,稀土元素配分曲线为右倾,其中LREE明显富集,HREE为不同程度亏损,具明显的负Eu异常;富集Rb、Th、Ce、Sm和亏损K、Ba、Ta、Hf、Y等元素,且为淡色花岗岩特征;据锆石Hf同位素测试分析,εHf(t)值为–2.35～+2.33和TDM2为962～1259 Ma,表明了花岗岩岩浆源区为壳幔混合的产物,以及源岩主要源自中元古代—新元古代陆壳基底物质的部分熔融.综合研究认为,始新世黑云二长花岗岩形成于喜马拉雅期碰撞造山向造山晚期转换阶段,是一套典型的"超厚地壳"部分熔融和壳幔相互作用的淡色花岗岩;以及其侵位时间代表了漕涧地区喜马拉雅碰撞造山阶段的完成和造山晚期阶段的开始,且转换时间约为35 Ma. 相似文献
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位于青蔵高原东北部的东昆仑造山带在晚二叠世到晚三叠世时期形成了大规模壳幔混合成因的花岗岩类,是研究壳幔相互作用和陆壳生长-再循环的理想场所.对该造山带的瑙木浑沟闪长玢岩岩体开展了详细的岩相学、LA-ICP-MS锆石U-Pb同位素年代学、矿物化学、岩石地球化学和Sr-Nd同位素的研究.结果显示,瑙木浑沟闪长玢岩形成年龄为215.6±3.4 Ma,属于晚三叠世岩浆作用的产物.斑晶主要由斜长石和角闪石构成,斜长石斑晶为中长石和少量拉长石,并具有正环带和反环带两种类型,角闪石斑晶属于浅闪石.闪长玢岩具有准铝质到弱过铝质、相对富Mg#（~51.2）和中-高钾钙碱性特点,轻稀土元素相对富集,重稀土元素相对亏损,富集Rb、Th、Ba和K等大离子亲石元素,亏损Nb、Ta和Ti等高场强元素,具有明显陆缘弧岩浆活动的特征.此外,岩石具有均一的ISr值（0.708 6~0.708 8）和相对较低εNd（t）（-5.3~-4.8）,并具有相对较古老的模式年龄TDM2（1.38~1.43 Ga）.上述矿物学和地球化学特征说明,闪长玢岩可能起源于富集的岩石圈地幔部分熔融形成的幔源岩浆上涌引发古老地壳熔融,并与壳源熔体均匀混合形成母岩浆,形成方式具有明显的MASH特征.结合区域地质研究,认为瑙木浑沟闪长玢岩可能形成于阿尼玛卿洋俯冲至晚期并向大陆碰撞的转换阶段,可能代表了巴颜克拉-松潘甘孜-东昆仑地体拼合的岩浆延迟反应产物.这对于理解造山带背景下从洋壳俯冲到陆-陆碰撞以及后碰撞过程的陆壳增长过程至关重要. 相似文献
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大别造山带早白垩世白鸭山A型花岗岩体中广泛分布着暗色微粒包体。对该包体及其寄主岩进行岩相学、矿物学和地球化学研究发现:镁铁质微粒包体(MME)与其寄主岩具有相同的矿物组合,相似的主量元素、微量元素和稀土元素特征,指示MME与寄主岩具有明显的亲缘关系;包体中岩浆成因褐帘石的发现,否定了富云包体的残余体成因,包体中含有碱性长石捕虏晶及大量针状磷灰石,指示岩浆混合作用的影响。结合共分母和不共分母图解判别,揭示MME与寄主岩明显具有岩浆混合作用特征,FeO*-MgO判别图解也指示包体为岩浆混合成因。Nd,Sr同位素组成指示MME的主体成分来源于富集岩石圈地幔,寄主岩体的物质来源为北大别杂岩。综合研究表明,大别地区在早白垩世存在一次壳幔混合作用,可能与岩石圈的伸展减薄有关,岩石圈的伸展导致富集地幔上涌,底侵并诱发古老下地壳熔融,同时发生岩浆混合作用。 相似文献
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东昆仑五龙沟花岗岩特征及其构造背景 总被引：2，自引：0，他引：2
根据岩石学、地球化学等特征及MC-ICP-MS锆石U-Pb定年,对东昆仑五龙沟地区花岗岩进行了构造环境研究。黄龙沟中粒正长花岗岩具有高硅、高碱、相对富铝、高FeOt/MgO和104Ga/Al值、富集轻稀土、明显的Eu负异常、相对原始地幔明显富集Zr、Ga、Y和Hf等高场强元素并强烈亏损Ba、Sr、P和Ti元素的特征,为A型花岗岩。锆石U-Pb法获得206Pb/238U值加权平均年龄为416.9±1.3 Ma,是早古生代晚志留世造山旋回末后造山碰撞产物,标志晚志留世东昆仑造山旋回进入造山后碰撞阶段。岩金沟矿区东花岗闪长岩为典型准铝质钙碱性花岗岩,具有I型花岗岩稀土元素特征,为I型花岗岩,形成年龄为258.9±2.1 Ma,属于昆南断裂结束后、于晚二叠世开始南区巴颜喀拉地体与昆中区南昆仑地体间发生强烈的壳幔剪切作用的产物。 相似文献
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内蒙古大青山地区古元古代花岗岩:地球化学、锆石SHRIMP定年及其地质意义 总被引：8，自引：5，他引：3
内蒙古大青山地区沿固阳-武川断裂带南侧发现一条古元古代花岗岩岩带,由石英闪长岩-闪长岩-角闪二长花岗岩组合构成.本文对其中典型代表厂汉脑包石英闪长岩、常福龙闪长岩和口子村角闪二长花岗岩进行了锆石定年和地球化学研究.地球化学上,石英闪长岩具有埃达克质花岗岩的特点,为低硅埃达克质花岗岩;大部分闪长岩具有赞岐岩的地球化学特征,部分具Closepet花岗岩特征;角闪二长花岗岩则全部具有Closepet花岗岩特征.根据锆石SHRIMP U-Pb定年,它们形成于2416~2435Ma之间,并遭受古元古代晚期构造热事件改造.表明在该区古元古代早期真正意义的板块构造已起作用,从岩浆演化的角度说明前寒武纪构造体制发生重大转变. 相似文献
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Orogenic and Anorogenic Granitoids in the Altay Mountains of Xinjiang and Their Discrimination Criteria 总被引：1，自引：0，他引：1
On the basis of field geological studies of the granotoids in the region, mineralogical, petrological, geochemical(including stable isotope geochemical) and isotopic geochronological investigations were carried out on selected representative granitic bodies of various types. The authors have concluded that, apart from the bodies of the orogenic granitoid series, there also exist intrusions of the anorogenic granitoid series in the region. The intrusives of the two series were formed not only in different ages and tectonic environments, but also were derived from different sources of materials. Moreover, they are associated with different mineralizations, belonging to different minerologenetic series(Cheng et al., 1983). They show distinctly a series of discriminative criteria. The problems under discussion in the present paper are of important theoretical and practical significance in the studies of granites of the orogenic belt, particularly the studies of the genesis and related metallogeny of the granites of the region. 相似文献
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Klaus Mezger Rainer Altherr Martin Okrusch Friedhelm Henjes-Kunst Hans Kreuzer 《Contributions to Mineralogy and Petrology》1985,90(4):353-366
The Kallithea intrusive complex on Samos forms part of the Miocene granitoid province of the central Aegean. The complex consists of numerous composite dikes consisting of different I-type diorites, monzodiorites, (quartz) monzonites, granodiorites, and granites, as well as rare pegmatites. Within individual dikes the different rock types display various structural relationships to each other, most of which indicate that multiple intrusion was the main process responsible for the association of different rock types. Petrographical, geochemical, and Sr isotope data prove that at least some of the different magma pulses were genetically unrelated. For others, a comagmatic relationship cannot be excluded. The most spectacular feature of the composite dikes are net-veined parts in which spherical (pillow-like) to angular bodies of microdiorite are surrounded by a network of more felsic rocks of varying compositions (monzonites, granodiorites, and monzogranites). — For the microdiorite/monzogranite pairs, a formation by unmixing due to liquid immiscibility is suggested by the following facts: (a) the presence of monzogranite ocelli within the microdiorite bodies, (b) similar compositions of those minerals present in both the basic and felsic parts, (c) the enrichment of HFS elements in the basic parts and the depletion of these elements in the acid parts, (d) similar Sr isotope initial ratios. Such an origin, however, is excluded for the other net-veined parts having felsic veins of either monzonitic or granodioritic compositions. In these pairs, the HFS elements are enriched in the acid parts, common minerals may have different compositions, and Sr isotope initial ratios are different. These net-veined parts can only be explained by the model of multiple injections whereby a felsic melt intruded into a basic magma. 相似文献
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桂东北越城岭岩体是一个由加里东期-印支期花岗岩组成的复式岩基,是目前南岭地区钨锡矿产调查评价的重点对象。本文选取该复式岩体中的加里东期不同岩性花岗岩,包括细粒花岗闪长岩、(粗)中粒斑状二长花岗岩和(中)细粒(斑状–含斑)二长花岗岩为研究对象,进行LA-ICP-MS锆石U-Pb年代学、矿物学、地球化学和Nd-Hf同位素组成研究。研究结果表明,细粒花岗闪长岩和(粗)中粒斑状二长花岗岩具有较低SiO_2(70%)含量和A/CNK值(0.99~1.05),较高CaO、TiO_2含量和FeO+MgO值,中等(La/Yb)N值以及中度亏损Ba、Sr、Eu元素等特征,副矿物以榍石为主加少量磁铁矿,属于I型花岗岩,形成时间为435~438 Ma;(中)细粒(斑状-含斑)二长花岗岩具有富硅(70%)、富碱、贫钙,高A/CNK值(1.04~1.14),低FeO+MgO值和(La/Yb)N值,中到重度亏损Ba、Sr、Eu元素等特征,副矿物含量低,以钛铁矿、独居石为主,为S型花岗岩,形成时间为423~429 Ma,略晚于前者。C/MF-A/MF图解反映I型花岗岩由变质中基性火成岩部分熔融形成,源区具有负且稳定的εNd(t)值(–7.1~–7.9)和εHf(t)值(–6.4~–7.8),平均地壳存留年龄为1.8 Ga左右。S型花岗岩的ε_(Nd)(t)值(–7.9~–8.8)和t_(Nd2DM)值(1.81~1.88 Ga)与I型花岗岩类似,但是其CaO/Na_2O值(0.28~0.64)和相对分散的ε_(Hf)(t)值(–2.6~–7.9)和t_(Hf2DM)值(1.57~1.90 Ga)说明源区可能存在变杂砂岩、变泥质岩和年轻地壳组分的三元混合,且以前两者为主。综合分析华南加里东造山带构造演化序列可以得知,造山带从褶皱缩短、逆冲加厚阶段向伸展垮塌阶段转化而形成的等温降压过程,是形成越城岭花岗岩的诱因。等温降压过程可以通过岩基旁侧新宁-资源深大断裂的松弛调整来实现。 相似文献
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The Vorontsovskii terrane of the Eastern Sarmatian orogen underwent HT/LP metamorphism at temperatures of 430–750°C and pressures of 3–5 kbar. The TIMS monazite age of this metamorphism is 2067 ± 9 Ma and corresponds to the most probable age range (2050–2080 Ma) when large volumes of mafic and granitoid intrusions were emplaced. The time spans of the magmatic activity and metamorphic event are closely similar, which suggests that the melts could have served as sources of metamorphic heat. However, geological data on the relations between the metamorphic zones and magmatic bodies (the largest of the mafic, diorite, and granitoid intrusions are hosted in zones of low-temperature metamorphism) and the occurrence of relict metamorphic mineral assemblages and crystallization foliation in metapelite xenoliths in these intrusions suggest that the intrusions were emplaced after the metamorphism. The most probable reason for the HT/LP metamorphism was an increase in the heat flux in the course of viscous deformations and folding in the warm lithosphere of the young Paleoproterozoic Vorontsovskii terrane during collision processes. 相似文献
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The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton 总被引：2，自引：0，他引：2
D. Barrie Clarke Krista L. McCuish Ron H. Vernon Victor Maksaev Brent V. Miller 《Lithos》2002,61(3-4):141-159
The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system. 相似文献
19.
蒙古国呼勒德地区正长岩锆石SHRIMP铀-铅年龄及其地质意义 总被引：1，自引：0，他引：1
呼勒德稀土元素矿化区位于蒙古国中戈壁省南部, 区内稀土元素和金矿(化)点星罗棋布, 为蒙古中南部最重要的金属矿化集中区之一。在所有上述矿床(点)中, 稀土元素矿化在下二叠统火山-沉积岩内呈似层状、脉状和透镜体状产出, 并且与呼勒德碱性正长岩株具有密切空间分布关系。本次研究对呼勒德正长岩进行了锆石SHRIMP铀-铅同位素年龄测定, 所获同位素年龄值为(214.3 ± 2.5)Ma, MSWD值为0.52, 属中生代印支期。根据上述同位素年代学数值, 同时结合其他地质与地球化学证据, 可以推测, 中生代时期, 受古陆块内部构造应力调整作用影响, 呼勒德地区一带及东西两侧曾发生过强烈构造-岩浆活动, 并且形成碱性正长岩株及相关的稀土元素矿(化)点。印支期碱性岩浆活动不仅为稀土元素矿(化)点的形成提供了物质、动力和热力来源, 而且是成矿流体对流循环的“发动机”。对比分析结果表明, 呼勒德碱性正长岩体的形成时间与南蒙古鲁金郭勒碱性花岗斑岩脉及相关稀土元素矿床形成时代大体相似, 它们均是地壳演化特定阶段混源(壳、幔源)岩浆活动的产物。 相似文献
20.
N. N. Kruk V. V. Golozubov T. B. Bayanova S. A. Kasatkin 《Russian Journal of Pacific Geology》2016,10(2):132-140
The geological, geochemical, and geochronological data on the granitiods of the Shmakovka massif, which represents a petrotype of the synonymous complex (southern Russian Primorye), show that the granitoid intrusions of the Shmakovka Complex play a “coupling” role, occurring in different blocks of the Khanka composite terrane. The geochemical and isotopic features of the granitoids indicate that their formation resulted from melting of a “mixed,” substantially metapelite, source similar to the most intensely metamorphosed rocks of the Khanka massif. According to U–Pb measurements, the granitoids are 490 ± 1 Ma old. The analysis of the distribution of Early Paleozoic I-, S-, and A-type granitoids in southern Primorye reveals that Late Cambrian–Early Ordovician endogenic events marked the amalgamation of Precambrian–Early Paleozoic blocks and the eventual formation of the Bureya–Jiamusi superterrane (Bureya–Khanka orogenic belt). 相似文献