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1.
华南陆壳改造系列花岗岩类型划分和成岩物质来源 总被引：43，自引：3，他引：43
本文将华南陆壳改造系列花岗岩进一步划分为同造山混合花岗岩和岩浆花岗岩型、非造山陆壳重熔型和同碰撞型3类。根据锶、钕同位素测定值,依壳、幔二元混合模型方法计算了3类花岗岩源区物质的构成:第一类型为上壳端元占78.6—89.7％,亏损地幔端元占15.0—10.3％;第二类型为上壳端元占63.7％,亏损地幔端元占36.3％;第三类型上壳端元占100％。均以上壳端元为主。 相似文献
2.
花岗岩类的地质环境—成因分类 总被引：2，自引：0，他引：2
根据成岩地质环境和岩石成因，花岗岩类总的可分为三大类，（１）板块俯冲－碰撞型－壳源重熔型（简称重熔型）及板块俯冲－碰撞型－壳幔混合源（心个地幔物质来源为主）同熔型（简称同熔型）成对花岗岩。（２）裂谷型－幔源分异型（简称分异型）花岗岩类，它包括大陆裂谷型－分异型碱性花岗岩和大洋裂谷型－分异型大洋斜长花岗岩两类。（３）地槽型－壳幔混合源（以陆壳或上地幔物质来源为主）花岗岩化型（简称花岗岩化型）花岗岩类 相似文献
3.
我国花岗岩型铀矿床集中产出在华南陆壳成熟度较高的特定部位,其特征是:地壳厚度大(莫霍面深度大干36km);陆壳增生范围宽(1000km以上),地壳铀含量偏高,其中沉积壳层平均铀含量为5.69ppm,花岗岩的平均铀含量为10.5ppm。产铀花岗岩体的源岩物质来自地壳,是陆壳多次增生和重熔分异的产物。对花岗岩型铀矿床的物质成分、元素组合及同位素组成的研究表明,成矿物质主要来自地壳岩石,是华南地壳多次活化改造的结果。 相似文献
4.
个旧锡矿区两个成岩系列的演化 总被引：2，自引：0，他引：2
根据岩浆岩的物源、岩类、物化特征及成因将个旧地区的火成岩划分为幔源分异系列和壳源重熔系列。幔源分异系列经历了从火山岩到侵入岩演化阶段,火山岩阶段由拉斑玄武岩系经高铝玄武岩系演化到碱性玄武岩系;侵入岩阶段由基性演化到碱性岩浆岩(斑岩)。壳源重熔系列在矿区仅有重熔岩浆阶段,经历了从混染型(斑状)到侵入型(粒状)花岗岩的发展过程。 相似文献
5.
锶同位素初始比值在划分花岗岩成因类型上的应用探讨 总被引：2，自引：0，他引：2
本文根据吴利仁的锶同位素初始比值(Ⅰ值)演化图解,计算出划分花岗岩成因类型分界线的三条直线方程:(1)幔源型与幔壳混源型分界线方程;(2)混源型与壳源型分界线方程;(3)壳源型中,下地壳与上地壳分界线方程。只要知道一个花岗岩体的形成年龄和Ⅰ值,就可以根据三个方程的分界值准确地判定其成因类型。这种利用Ⅰ值线方程定量地划分花岗岩成因类型的方法,符合Ⅰ值随时间推移而增长的规律,比目前采用的固定值法更加合理。此外,根据(1)、(2)二个方程,应用杠杆原理,还可大致估计幔、壳源岩的百分比。 相似文献
6.
不论花岗岩是交代成因的,还是岩浆成因的,其形成的过程主要是在大陆壳的范围内进行的。交代成因的花岗岩,自不待言交代前钓源岩是陆壳的岩石;而花岗岩浆,除极少数是地幔源的玄武岩浆结晶分异晚期的产物,或直接来自地幔中的石榴石二辉橄榄岩部分熔融外,绝大多数花岗岩浆都是大陆壳重熔或部分熔融形成的。 相似文献
7.
广西花岗岩类分布广泛,出露面积近二万平方公里。据可靠的地质及同位素年龄资料,将岩体划分为四堡期、雪峰期、加里东期、华力西期、印支期、燕山期。花岗岩岩类多样,且与内生金属成矿有密切关系。本文在1∶20万区调工作所取得的丰富资料基础上,拟就广西花岗岩类成因分类及其特征、演化作初步探讨。据广西花岗岩类的地质背景,岩石学、岩石化学、副矿物、成矿、同位素组成等方面的显著差异,将花岗岩类初步划分为幔源分异型、壳源交代型、壳源重熔型、混合源同熔型。 (一)幔源分异型(简称分异型):系上地幔玄武岩浆分异产物,并有硅铝层物质混 相似文献
8.
阿尔泰花岗岩类型与成岩模型的REE及O、Pb、Sr、Nd同位素组成依据 总被引：2，自引：0，他引：2
根据 REE 分布模式和 O、Pb、Sr、Nd 同位素组成特征,采用构造环境、物质来源和形成方式等多级标准,将阿尔泰花岗岩类划分为两个系列、五种类型,即造山花岗岩系列(阿尔泰系列),包括:壳-幔同熔型(青格里型),地壳交代型(额尔齐斯型),地壳重熔型(尚可兰型);非造山花岗岩系列(乌伦古系列),包括:幔源分异型(布尔根型),幔 相似文献
9.
华南两种类型花岗岩成岩-成矿作用的差异 总被引：5，自引：0，他引：5
华南地区主要产出两种类型的花岗岩类，一是壳源的陆壳重熔型花岗岩类，二是壳-幔混源的钙碱型浅成花岗岩类。二者不仅在成因上有很大差别，在成矿作用上也明显不同。本文通过实例，探讨了这两种类型花岗岩在成岩-成矿关系上的差异。研究表明，陆壳重熔型花岗岩类的成岩与对应的成矿作用之间存在着明显的时间差，以南岭地区为例，在燕山中期第一阶段170~150 Ma达到高潮的陆壳重熔型花岗岩类，其相关的钨锡等稀有金属矿化多发生在燕山中期第二阶段150~139 Ma，成岩与成矿相差10~20 Ma，这一时间差反映了这类花岗岩成岩作用与成矿作用之间在物质来源和地质构造背景等方面的差异。而那些壳-幔混源的钙碱型浅成花岗岩类，由于其成岩时就具备这种条件，因此成岩-成矿基本同时，没有明显的时间差。由此可见，大规模金属成矿作用主要与拉张的动力学背景、壳-幔相互作用、高的热流值，以及深部流体的参与密切相关。 相似文献
10.
滇西地区花岗岩根据其物源及岩石特征可划分为幔源分异和壳源重熔两大岩石系列,并将壳源重熔系列细分为三个成因类型和相应的成岩阶段。本文着重探讨壳源重熔花岗岩的时空分布、地质特征、演化及其与锡-多金属成矿的关系。滇西地区壳源重熔花岗岩纵向上可以构成一个完整的成岩成矿系列,横向上随同一类花岗岩岩浆分异又演化为若干亚系列。云龙锡矿带的志本山、石缸河和铁厂锡矿床是混染型亚系列系统演化的实例。 相似文献
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Proterozoic Gremyakha-Vyrmes Polyphase Massif, Kola Peninsula: An example of mixing basic and alkaline mantle melts 总被引：1，自引：0，他引：1
The paper presents newly obtained data on the geological structure, age, and composition of the Gremyakha-Vyrmes Massif, which consists of rocks of the ultrabasic, granitoid, and foidolite series. According to the results of the Rb-Sr and Sm-Nd geochronologic research and the U-Pb dating of single zircon grains, the three rock series composing the massif were emplaced within a fairly narrow age interval of 1885 ± 20 Ma, a fact testifying to the spatiotemporal closeness of the normal ultrabasic and alkaline melts. The interaction of these magmas within the crust resulted in the complicated series of derivatives of the Gremyakha-Vyrmes Massif, whose rocks show evidence of the mixing of compositionally diverse mantle melts. Model simulations based on precise geochemical data indicate that the probable parental magmas of the ultrabasic series of this massif were ferropicritic melts, which were formed by endogenic activity in the Pechenga-Varzuga rift zone. According to the simulation data, the granitoids of the massif were produced by the fractional crystallization of melts genetically related to the gabbro-peridotites and by the accompanying assimilation of Archean crustal material with the addition of small portions of alkaline-ultrabasic melts. The isotopic geochemical characteristics of the foidolites notably differ from those of the other rocks of the massif: together with carbonatites, these rocks define a trend implying the predominance of a more depleted mantle source in their genesis. The similarities between the Sm-Nd isotopic characteristics of foidolites from the Gremyakha-Vyrmes Massif and the rocks of the Tiksheozero Massif suggest that the parental alkaline-ultrabasic melts of these rocks were derived from an autonomous mantle source and were only very weakly affected by the crust. The occurrence of ultrabasic foidolites and carbonatites in the Gremyakha-Vyrmes Massif indicates that domains of metasomatized mantle material were produced in the sublithospheric mantle beneath the northeastern part of the Fennoscandian Shield already at 1.88 Ga, and these domains were enriched in incompatible elements and able to produce alkaline and carbonatite melts. The involvement of these domains in plume-lithospheric processes at 0.4–0.36 Ga gave rise to the peralkaline melts that formed the Paleozoic Kola alkaline province. 相似文献
13.
We trace source variations of active margin granitoids which crystallised intermittently over ~300 Ma in varying kinematic regimes, by combining zircon Lu-Hf isotopic data from Early Palaeozoic to Early Jurassic igneous and metaigneous rocks in the Mérida Andes, Venezuela and the Santander Massif, Colombia, with new whole rock Rb/Sr and Sm-Nd isotopic data, and quartz O isotopic data. These new data are unique in South America because they were obtained from discrete magmatic and metamorphic zircon populations, providing a high temporal resolution dataset, and compare several isotopic systems on the same samples. Collectively, these data provide valuable insight into the evolution of the isotopic structure of the continental crust in long-lived active margins.Phanerozoic active margin-related granitoids in the Mérida Andes and the Santander Massif yield zircon Lu-Hf model ages ranging between 0.77 Ga and 1.57 Ga which clearly define temporal trends that can be correlated with changes in tectonic regimes. The oldest Lu-Hf model ages of >1.3 Ga are restricted to granitoids which formed during Barrovian metamorphism and crustal thickening between ~499 Ma and ~473 Ma. These granitoids yield high initial 87Sr/86Sr ratios, suggesting that evolved, Rb-rich middle to upper crust was the major source of melt. Granitoids and rhyolites which crystallised during subsequent extension between ~472 Ma and ~452 Ma yield younger Lu-Hf model ages of 0.80 Ga–1.3 Ga and low initial 87Sr/86Sr ratios, suggesting that they were derived from much more juvenile, Rb-poor sources such as mafic lower crust and mantle-derived melts. The rapid change in magmatic sources at ~472 Ma can be attributed either to reduced crustal assimilation during extension, or a short pulse of crustal growth by addition of juvenile material to the continental crust. Between ~472 Ma and ~196 Ma Lu-Hf model ages remain mostly constant between ~1.0 and ~1.2 Ga. The large scatter and the absence of definite trends in initial 87Sr/86Sr ratios suggest that both mafic, Rb-poor, and evolved Rb-rich sources were important precursors of active margin magmas in Colombia and Venezuela throughout the Palaeozoic to the Early Jurassic.Previous studies have shown that the genesis of arc magmas may be stimulated by heat advection to the crust during the underplating of mantle derived melt, but the absence of permanent younging trends in Lu-Hf model ages from ~472 Ma to ~196 Ma suggests that very little new crust was generated during this period in the studied region. An overwhelming majority of the analysed igneous rocks yield zircon Lu-Hf model ages of >1 Ga which may be accounted for by documented local crustal end members of 1 Ga–1.6 Ga, and do not require contributions from the depleted mantle. Therefore, recycling of ~1 Ga and older crust was a dominant process in the north-western corner of Gondwana between ~472 Ma and ~196 Ma.This study shows that whole rock Sm-Nd and zircon Lu-Hf data can be interpreted similarly regarding the age of the source regions, whereas Rb-Sr and O isotope data from the same rocks yield valuable information regarding the geochemical nature of the source. 相似文献
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济阳凹陷火山岩的岩石学与地球化学 总被引：3，自引：1，他引：3
对济阳凹陷的第三系火山岩、基性侵入岩进行了岩石学和地球化学研究,分别总结了火山岩、基性侵入岩岩石类型及其特征。碱性系列玄武岩主要为钠质系列,具上地幔来源的特征。从古新统到渐新统,玄武岩熔融程度降低,岩浆地幔源深度增加。微量元素和同位素的数据表明,第三纪火山岩源区存在不协调现象。稀土元素分析表明,本区玄武岩为大陆裂谷成因。钐-钕、铷-锶及铅同位素的数据表明,火山岩与侵入岩同源,都来自上地幔。玄武岩浆在形成过程中有过不同程度的混合作用,Rb/Sr相关性表明早、晚第三纪的幔源类型上存在差别。第三纪火山岩数据点分布于DMM,EMIH和EMII三个端元之间,反映第三纪火山岩成因与这三个端元不同程度混合有关。本区火山岩成因与幔源有关,地幔不相容成分的特征表明有沉积物混入的可能,不排除是陆壳物质混入,不同深度岩浆的混合也是一种解释。 相似文献
16.
《Russian Geology and Geophysics》2007,48(2):141-156
The Erdenet-Ovoo magmatic center (EOMC) lies within the North Mongolian magmatic area formed through the interaction of a Permo-Triassic plume with the lithosphere in an environment of active continental margin. Two stages are recognized in the EOMC history: subduction stage with participation of basalt-andesite-dacite-rhyolite series and rifting stage with trachybasalt series. The granitoid magmatism (258–220 Ma) is expressed as the Selenge, Shivota, and ore-bearing porphyry complexes. The formation of the Selenge and Shivota granitoids was preceded by the intrusion of gabbroids. Trachybasalts formed during the granitoid magmatism after the Selenge complex, nearly synchronously with the Shivota and ore-bearing porphyry complexes. At the subduction stage of the EMC evolution, the plume influence is documented from the appearance of gabbros both depleted and enriched in lithophile trace elements similar to volcanic rocks of trachybasalt series and basaltoids of bimodal series in northern Mongolia. The Rb-Sr and Sm-Nd isotope characteristics of the enriched gabbros suggest the participation of a lower mantle source in their formation. The plume, as a heat carrier, led to a large-scale manifestation of volcanism and, obviously, a wide development of basic rocks of this stage at depth. The basic rocks were the source of granitoid magma that produced the Selenge granitoids. The protolith melted in the >50 km thick crust preventing the wide manifestation of basaltoid volcanism in that period. The increased plume influence, rifting, uplift of the region, and extension of the crust favored the basaltoid and granitoid (Shivota and ore-bearing porphyry) magmatism activity. 相似文献
17.
Classification and Source Materials of Continental Crust Transformation Series Granitoids in South China 总被引：7，自引：2，他引：7
The granitoids of the continental crust transformation series in South China may be divided into threetypes: (1) synorogenic migmatic and magmatic type. (2) anorogenic continental crust anatexis type, and (3)syncollision type. Based on the results of Sr and Nd isotopic determinations, the source material compositionof the three types of granitoids is calculated with crust-mantle binary mixing simulation. The calculations indi-cate that the granitoids of the first type consist of 78.6-89.7% upper crust endmember materials and15.0-10.3% depleted mantle endmember materials, the granitoids of the second type are composed of 63.7%upper crust endmember materials and 36.3% depleted mantle endmember materials, and those of the third type100% upper crust endmember materials. Hence. the source material composition of the granitoids of all thethree types is dominated by upper crust endmembers. 相似文献
18.
A. M. Larin A. B. Kotov S. D. Velikoslavinskii E. B. Sal’nikova V. P. Kovach 《Petrology》2012,20(3):218-239
Systematized geological, geochronologic, geochemical, and Sm-Nd isotopic geochemical data obtained over the past decade on A-granitoids in the Aldan Shield and in adjacent mobile belts surrounding it in the south make it possible to identify the sources from which the rocks were derived and the geodynamic environments in which they were generated. The territory in question provides evidence of five episodes of Early Precambrian within-plate magmatism, including the derivation of A-granites: at 2.62, 2.40?C2.52, 2.07, 1.87?C1.88, and 1.70?C1.74 Ga. Although all of the granitoids were derived within plates, the environments of their derivation were different: (i) postcollisional lithospheric extension at 2.64 and 1.87?C1.88 Ga in an anorogenic environment and (ii) in relation to the activity of mantle plumes at 2.40?C2.52, 2.07, 1.74?C1.70 Ga. The postcollisional magmatism generated only potassic granitoids of the subalkaline type, whereas the anorogenic magmatic rocks comprise both subalkaline granitoids (of K series) and alkaline granites (of Na series), which are intensely fractionated and strongly enriched in incompatible elements. A-granitoids in the Aldan Shield and its surrounding folded structures were derived from mixed mantle-crustal sources. The sources of the subalkaline granitoids were dominated by the material of the continental lower crust, while the alkaline granitoids were derived from mantle sources. Thereby the mantle source material of the anorogenic granitoids consisted of an OIB-type component, and the postcollisional granitoids were derived from MORB and OIB sources. 相似文献
19.
江苏盘石山二辉橄榄岩包体的Nd、Sr、Pb同位素特征 总被引：7，自引：4，他引：7
对盘石一带的６个二辉橄榄岩包体，３个单斜辉石的Ｎｄ、Ｓｒ同位素，４个全岩、７个单斜辉石和１个斜方辉石的铅同位素进行了测定。结果表明，它们在亏损的岩石圈中经历了长时间的演化，其Ｒｂ－Ｓｒ、Ｓｍ－Ｎｄ、Ｐｂ－Ｐｂ同位素体系的相关性可能反映了不同时期的地幔过程。位于陆下岩石圈地幔中上部位的包体比下部岩石圈地幔具有相对亏损和不均一的同位素特征。 相似文献
20.
西藏崩纳藏布和甲岗雪山地区花岗岩的地球化学特征及成因初探 总被引：11，自引：0，他引：11
西藏申扎县崩纳藏布和甲岗雪山两个地区出露的岩浆岩体一直被认为是两个较大的花岗岩基，但实际地质调查表明，这两个岩体中的每一个都可以分解为多个不同岩性的小岩体，K—Ar同位素年龄表明，这些岩体主要形成于燕山晚期(90．55Ma-114．67Ma)和喜山早期(58．75Ma)。对其中部分岩体开展的微量元素、稀土元素以及Rb—Sr和Sm—Nd同位素的地球化学初步研究表明，两地出露的花岗岩体虽然形成于不同时代，但具有相同的以壳幔混合带为主的源区。另一方面．痕量元素的含量及同位素的组成特征也同时表明了形成于不同时期的岩体具有含量、配分、趋势变化等方面的差异，反映其具体的成因和分异演化过程并不相同。 相似文献