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1.
对我国港边岩浆混合杂岩体进行系统的地质学、岩石学和矿物学研究，并将其分解为偏酸性端夺浆、基性端元岩浆、混合岩浆和非岩浆混合物４个单元，从不同的角度探讨了岩事和分离结晶作用同时发生对岩浆混合岩成分的制约，提出存在化学和机械两种岩交混合方式，证明了它们与基性岩侵放一起构成一个连续的岩交作用序列，最天野外造背景的判别综合提出港边港混合杂岩体的构造－岩浆模型。 相似文献
2.
赣东北晚元古代港边岩浆混合杂岩体的区域地质调查及岩石学研究 总被引：13，自引：0，他引：13
赣东北横峰县港边岩体是我国罕见的填图尺度上表示的岩浆混合杂岩体。该杂岩体出露于古江南造山带的南侧，实际上它是该造山带晚元古代增生柱内岩浆混合作用的典型产物。文章从地质学、岩相学和岩石地球化学等不同角度确证港边岩浆混合杂岩体形成于开放体系下岩浆演化的独特方式－－岩浆混合作用。因此，我们在填图时没有采用封闭体系下岩浆演化的谱系单元－超单元方法，而是以岩浆混合作用理论为基础，应用端员－混合物－端员的区域地质测量方法对港边岩浆混合杂岩体进行了有效的分解和研究。 相似文献
3.
浙江普陀花岗杂岩体中的石英闪长质包体：斜长石内部复杂环带研究与岩浆混合史记录 总被引：11，自引：7，他引：11
浙江普陀花岗杂岩体包含若干石英闪长质包体,该类包体中存在三种不同类型的斜长石:正常环带的斜长石、筛孔构造的斜长石和酸性斜长石为核的“反环带”斜长石。根据斜长石的环带构造特征和成分分析,认为本区的岩浆演化过程大致如下:下部基性岩浆注入到上覆酸性岩浆中并进行混合作用,酸性岩浆中已结晶的富钠质斜长石晶体进入偏基性的混合岩浆中,部分熔融形成筛孔构造;随着端员岩浆的进一步混合,富钠质斜长石晶体与中性混合熔体仅形成粗糙的边界,而保留原先构造特征;同时混合岩浆可以直接结晶出正常环带斜长石,呈单颗粒或以膜的形式包围其它环带构造的长石。本文还通过与平潭甬闪辉长岩杂岩体内筛孔斜长石的对比,认为斜长石的环带构造和成分可以反映岩浆源区特征和岩浆演化历史。 相似文献
4.
赣东北港边火成杂岩体岩浆混合作用结构类型与成因机理 总被引：3，自引：0，他引：3
赣东北前寒武纪港边火成杂岩体广泛发育不同类型的矿物间不平衡结构,指示该杂岩体曾发生过广泛的岩浆混合作用。对该杂岩体进行详细的薄片岩石学研究,总结了岩浆混合结构类型,包括斜长石环边、角闪石环带、文象钾长石的环斑结构与斜长石反环斑结构、石英-角闪石眼球状、钾长石巨斑的角闪石环和蜂窝状的斜长石等混合结构类型;镁铁质包体中指示岩浆混合作用的结构类型:石英/钾长石嵌晶结构、榍石-长石眼球结构、叶片状黑云母、针状磷灰石结构、斜长石的细条状结构、斜长石的蜂窝状环和斜长石的海绵式蜂窝状熔融结构,对这些结构类型进行了成因机理讨论。 相似文献
5.
闽北建瓯大康闪长质杂岩的年代学及岩石地球化学研究 总被引：2，自引：0，他引：2
系统的同位素年代学及岩石地球化学研究表明，大康闪长质杂岩体的成岩时代为４９８．２Ｍａ±１５．４Ｍａ，成岩物质来源于壳／幔混合熔融。Ｓｒ，Ｎｄ同位素地球化学的研究进一步表明，大康闪长质杂岩应为华南同熔型岩浆系列中的较基性端员，岩体可能形成于俯冲带构造背景 相似文献
6.
桐庐、相山火山-侵入杂岩单颗粒锆石U-Pb年龄 总被引：48，自引：7，他引：41
利用单颗粒锆石Ｕ－Ｐｂ法分别测定了桐庐和相山火山－侵入杂岩中早期及晚期形成的岩石单元的结晶年龄,桐庐杂岩体中早期火山岩的喷发年龄为１３４．９Ｍａ,晚期浅成岩的结晶年龄为１３４．４Ｍａ,杂岩体基本上属于同时形成,为早白垩世岩浆活动的产物;相山杂岩体中第二阶段岩石的结晶年龄为１４０．３Ｍａ,最晚阶段超浅成岩的结晶年龄为１３５．４Ｍａ,杂岩体各单元的形成时间相近,为晚侏罗世末期岩浆活动的产物。可见利用单颗粒锆石Ｕ－Ｐｂ年龄能非常有效地讨论一套岩石组合是否是同时间形成的,而这正是火山－侵入杂岩研究的重要内容之一。 相似文献
7.
东昆仓中段白日其利岩体岩浆混合作用的初步研究 总被引：2，自引：0，他引：2
通过对岩体地质特征、暗色包体及Ｎｄ、Ｓｒ同位素资料研究表明：东昆仓中段中三叠世白日其岩体是由壳幔岩浆不均一或不彻底多次混合作用形成的,岩体内部呈出酸性、基性岩浆因混合程度和混合比例不同而形成复杂的岩体结构样式,其基性端元为混合不彻度而残留的辉长质岩石,酸性端元是受轻度混梁的二长花岗岩,岩浆混合作用方式以就是混合为主,岩体形成于碰撞造山期后的构造环境。 相似文献
8.
云南禄丰鸡街杂岩体中碱性超基性岩地球化学特征及成因探讨 总被引：3，自引：0，他引：3
本文总结了位于川滇裂谷带南段，滇中地区罗茨碱性超基性岩杂岩体群成员之一－鸡街杂岩体中碱性超基性岩的主要元素、过渡金属元素、大离子亲石元素、稀土元素和同位素地球化学特征；进而从原始岩浆确立、岩浆源岩模拟以及岩浆结晶分异作用等方面讨论了杂岩体中这类岩石的成因。 相似文献
9.
赣东北前寒武纪港边杂岩体的岩浆混合（和）作用及其地质意义 总被引：8，自引：0，他引：8
赣东北地区沿江绍断裂北缘和江南造山带南侧有大量的前寒武纪火山侵入杂岩呈带状分布,主要由大面积的陆相火山岩和若干长英质镁铁质火成杂岩体组成,后者中出露面积最大的港边杂岩体在填图尺度上可划分为长英质岩、镁铁质岩和过渡性岩3大组成部分,长英质岩颗粒锆石U_Pb谐和不一致曲线上交点年龄为822±4Ma,代表杂岩体中岩浆混合作用发生的时间。港边岩体中长英质岩石的Nd模式年龄为1·49~1·68Ga,镁铁质岩中玄武质岩石为1·51~2·21Ga,辉长岩的Nd模式年龄与玄武质岩石基本相同,为1·54~2·13Ga,经计算的过渡性岩石的Nd模式年龄为1·58~1·90Ga,因此认为镁铁质岩石从源区分离的时间要远早于长英质岩石,而过渡性岩石含有前两个端员岩浆相互混合(和)的信息。长英质岩石的εNd(t=822Ma)值为-0·8~-4·4,87Sr/86Sr(822)比值为0·70368~0·70549;玄武质岩石的εNd(822)值为-2·6~+2·3,87Sr/86Sr(822)比值为0·70387~0·70527,这反映了镁铁质岩浆的源区接近总地球,长英质岩浆则来自具壳幔混合性质的EMⅠ型地幔的源区。可以推测,赣东北前寒武纪也曾发生过岩浆底侵作用。底侵作用对港边火成杂岩体岩浆的形成起着重要的作用。底侵于壳幔边界的玄武质岩浆使地壳熔融形成长英质岩浆并聚集于浅部岩浆房。随着长英质岩浆房降温,长英质岩浆的结晶度和粘度增加,其物理状态发生液态→(固+液)混合态→固态的变化;当玄武质岩浆穿透下地壳并不断进入物理状态变化的长英质岩浆房时,持续地发生两种岩浆的化学混合作用或两岩浆的机械混合作用或玄武质岩浆的侵入,其混合作用的时间以长英质岩锆石的U_Pb谐和不一致曲线上交点年龄822±4Ma界定。根据Nd模式年龄(tDM)和Nd富集系数(fSm/Nd)分布特征,可以确定中元古代江南造山带为太古宙扬子古陆核的横向增生体,而新元古代陆相火山侵入杂岩带则横向增生于江南造山带南缘。至此,扬子古陆横向增生作用结束,开始与华夏古陆拼贴,包括港边火成杂岩体在内的新元古代火山侵入杂岩带则成为两古陆连结的纽带。 相似文献
10.
桂东南富钾岩浆岩岩的Nd同位素组成：华南中生代地幔物质上涌事件 总被引：16，自引：9，他引：16
广西东南部罗容杂岩体由辉长岩－闪长岩－二长岩－正长岩组成，马山由碱性辉长岩－正长岩－花岗闪长岩－花岗岩组成。它们富K、富大离子亲石元素（LIL），无Nb、Ta负异常等特征表明它们是形成于板内环境的钾玄质侵入岩。罗容杂岩体的各种岩石和马山的基性岩的εNd(T)稍低，为－0．6，此岩石单元是由幔源岩浆加热地壳使之熔融的壳源岩浆形成的，并伴有幔源岩浆的混合或交换。此二杂岩体形成于拉张构造环境。地幔物质上涌导致了中生代华南地壳张裂以及华南大规模花岗岩和相关矿床的形成。 相似文献
11.
赣东北前寒武纪岩浆混合作用岩带的发现及其地质意义 总被引：8，自引：0，他引：8
在总结新近发现的赣北前寒武纪岩浆混合岩带地质特征的基础上,从地质学、岩相学和同位素地球化学的角度,论证了发生于这一特殊地质时期和地质背景下的岩浆混合作用。文中将该作用形成的岩浆混合杂岩体有效地分解为：（１） 偏酸性端员的岩浆岩（ 角闪石英正长岩、石英正长岩） ;（２） 基性端员岩浆岩（ 玄武玢岩、玄武安山玢岩） 和（３） 岩浆混合岩,后者又可分为非均一岩浆混合岩和均一岩浆混合岩（ 如石英二长闪长岩） 。阐明该岩浆混合作用是新元古期我国东南地区江南古洋向扬子古陆俯冲消减这一构造演化的重要物质表现;示踪该地区于中元古期（１４８ ～１８５ Ｇａ） 经历了一次与全球范围一致的壳 幔分离事件和新元古期（０８５ Ｇａ） 亏损地幔与大洋沉积物在源区混合的事件;确认该地区前寒武纪的岩浆混合作用和岩浆侵入作用实际上是一个连续的岩浆作用序列,并且两者受近南北向挤压的同一应力场条件所制约 相似文献
12.
Magma mixing in the Sithonia Plutonic Complex, Greece: evidence from mafic microgranular enclaves 总被引：20，自引：1，他引：20
Summary ¶Mafic microgranular enclaves occur in most calc-alkaline granitoids, and it is widely accepted that they represent the remnants of basic magmas that interacted with more acid magmas. In this work we present new data on mafic microgranular enclaves occurring in the granodiorites of the Sithonia Plutonic Complex (Northern Greece). Enclave properties have been studied using different methods. Quantitative textural analysis has been carried out in order to decipher the crystallization history of enclaves once they have been entrained in the more acid and cooler host magma. In particular, the nucleation density (C), the mode (M) and the crystal index (n) of enclaves has been measured. Along with textural analysis, the size of enclaves has also been estimated using a method that, based on two-dimensional sections of enclaves, allows the estimation of volume of enclaves. Geochemical analyses have been performed to investigate the degree of chemical interaction that enclaves suffered from the host acid magma. The different data sets have been utilized to furnish a general evolutionary model of the magmatic interaction process between the basic and the acid magmas that led to the formation of the granodioritic host rock and related mafic microgranular enclaves. It is concluded that, as the magmatic interaction process proceeded, the crystallization of enclaves involved the nucleation of apatite and epidote (first stage of crystallization) followed by biotite, ± hornblende, plagioclase, and titanite (second stage of crystallization); the last minerals that nucleate were quartz and K-feldspar. During crystallization enclaves underwent contamination by the host acid magma through flow channels opened during the transfer of mineral phases from the host magma to the enclaves. When the two magmas attained similar rheological behaviour a two-end member mixing process was favoured inducing progressively more vigorous mixing dynamics. Volumetric analysis of enclaves indicates that the smaller ones suffered a more intense geochemical interaction compared to the larger ones. We interpret this evidence as being strictly related to the kinematics of the mixing process, the latter governed by chaotic dynamics. Enclaves are viewed as portions of the basic magma that did not mix completely with the acid host magma and survived the mixing process. Host rocks are considered as volumes of the magmatic system where the more efficient mixing dynamics produced different, generally higher, degrees of hybridisation.Received May 22, 2002; revised version accepted November 5, 2002
Published online February 24, 2003 相似文献
13.
R Elangovan Kumar Krishna Neeraj Vishwakarma K R Hari M Ram Mohan 《Journal of Earth System Science》2017,126(7):92
Field and petrographic studies are carried out to characterize the interactions of mafic and felsic magmas from Pithora region of the northeastern part of the Bastar Craton. The MMEs, syn-plutonic mafic dykes, cuspate contacts, magmatic flow textures, mingling and hybridization suggest the coeval emplacement of end member magmas. Petrographic evidences such as disequilibrium assemblages, resorption textures, quartz ocelli, rapakivi and poikilitic textures suggest magma mingling and mixing phenomena. Such features of mingling and mixing of the felsic and mafic magma manifest the magma chamber processes. Introduction of mafic magmas into the felsic magmas before initiation of crystallization of the latter, results in hybrid magmas under the influence of thermal and chemical exchange. The mechanical exchange occurs between the coexisting magmas due to viscosity contrast, if the mafic magma enters slightly later into the magma chamber, then the felsic magma starts to crystallize. Blobs of mafic magma form as MMEs in the felsic magma and they scatter throughout the pluton due to convection. At a later stage, if mafic magma enters the system after partial crystallization of felsic phase, mechanical interaction between the magmas leads to the formation of fragmented dyke or syn-plutonic mafic dyke. All these features are well-documented in the study area. Field and petrographic evidences suggest that the textural variations from Pithora region of Bastar Craton are the outcome of magma mingling, mixing and hybridization processes. 相似文献
14.
MO Xuanxue DONG Guochen ZHAO Zhidan GUO Tieying WANG Liangliang CHEN Tao 《《地质学报》英文版》2005,79(1):66-76
Abstract Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdisê giant magmatic belt, within which the Qüxü batholith is the most typical MME‐bearing pluton. Systematic sampling for granodioritic host rock, mafic microgranular enclaves and gabbro nearby at two locations in the Qüxü batholith, and subsequent zircon SHRIMP II U‐Pb dating have been conducted. Two sets of isotopic ages for granodioritic host rock, mafic microgranular enclaves and gabbro are 50.4±1.3 Ma, 51.2±1.1 Ma, 47.0±1 Ma and 49.3±1.7 Ma, 48.9±1.1 Ma, 49.9±1.7 Ma, respectively. It thus rules out the possibilities of mafic microgranular enclaves being refractory residues after partial melting of magma source region, or being xenoliths of country rocks or later intrusions. Therefore, it is believed that the three types of rocks mentioned above likely formed in the same magmatic event, i.e., they formed by magma mixing in the Eocene (c. 50 Ma). Compositionally, granitoid host rocks incline towards acidic end member involved in magma mixing, gabbros are akin to basic end member and mafic microgranular enclaves are the incompletely mixed basic magma clots trapped in acidic magma. The isotopic dating also suggested that huge‐scale magma mixing in the Gangdisê belt took place 15–20 million years after the initiation of the India‐Asia continental collision, genetically related to the underplating of subduction‐collision‐induced basic magma at the base of the continental crust. Underplating and magma mixing were likely the main process of mass‐energy exchange between the mantle and the crust during the continental collision, and greatly contributed to the accretion of the continental crust, the evolution of the lithosphere and related mineralization beneath the portion of the Tibetan Plateau to the north of the collision zone. 相似文献
15.
The Blue Tier Batholith is one of a number of high-level, essentially postkinematic, composite granitoid bodies occurring at the southern end of the Tasman orogenic belt of Eastern Australia.An integrated study of the structure, texture, and geochemistry of the batholith suggests that it has a cumulate-like character. In particular, the trace element (Ba, Rb, Sr) data, when constrained by textural features of the granitiods, indicate that the batholith formed by fractional crystallization of a single magma which underwent crystallization in situ by progressive nucleation and solidification from the roof, walls, and floor inwards. Progressive changes in liquids (cumulate) mineralogy during crystallization led to the observed sequence of early biotite and/or hornblende granodiorites followed by biotite adamellites and late muscovite biotite granites. Progressive in situ crystallization led in some instances to gradational boundaries between granitoid types whereas periodic tectonic distrubances caused the rest magma to reintrude earlier crystallizates in places: thus emplacement and crystallization sequences are parallel. The ultimate product of fractional crystallization was a water-saturated melt, enriched in incompatible elements, whose crystallization resulted in significant tin mineralization.The chemistry of the rocks comprising the batholith is in many respects analogous to that of basic cumulate rocks, although an origin by outward growth of crystals and expulsion of interstitial melt, coupled with convective mixing, rather than by crystal settling, is favoured for the granitoid suite. It is suggested that the Blue Tier Batholith is not an isolated example of a granitoid body with cumulate-like character, but that such bodies may be more common than is recognized. 相似文献
16.
The igneous rocks of the Kialineq centre on the coast of East Greenland at 67°N include a number of quartz syenite and granite plutons intruded 35my BP. These are subvolcanic bodies emplaced by cauldron subsidence and with ring-dike and bell-jar form. Associated with the major intrusions is an extensive acid-basic mixed magma complex. Two-liquid structures, chilling of basic against acid magma, pillows of basic in acid, and net-veining of basic by acid magma, are superbly displayed. The basic magma was of a transitional or alkaline type and underwent varying degrees of fractionation in a regime of repeated intrusions and diverse chambers. Heterogeneous hybrid rocks intermediate between basalt and quartz syenite are strongly developed and were formed by repeated mechanical mixing of contrasting magmas. The energy for this mixing probably came in the main from cauldron-block subsidence. The quartz syenite magma, which itself fractionated towards granite, has initial 87Sr/86Sr ratios the same as the basic magma and is itself believed to be a fractionation product of alkali basalt magma. 相似文献
17.
桐柏北部黄岗侵入杂岩岛弧构造环境的厘定 总被引：1，自引：0，他引：1
出露于北秦岭桐柏北部的黄岗侵入杂岩形成于早古生代 ,有超基性、基性和中酸性岩石产出 ,以中酸性岩石为主。主量元素和微量元素地球化学特征显示 ,黄岗侵入杂岩是同源岩浆分异结晶的产物 ,同位素示踪反映岩浆中含有一定比例的陆壳物质。分析表明 ,黄岗侵入杂岩形成于类似大洋板块俯冲的岛弧构造环境 ,与二郎坪弧后盆地向北的俯冲消减有密切联系 ,其中的陆壳物质来自俯冲板上陆壳沉积物的再循环。 相似文献
18.
Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in
magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing,
fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline
(CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally
diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from
mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately
preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl
volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low
pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40–50) and lack Ca-poor pyroxene.
Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA).
TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al
basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the
Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some
indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks
Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure
mineral assemblage of high-Al basalt results from crystallization at higher crustal levels. 相似文献
19.
北京燕山地区薛家石梁杂岩体特征、成因、源区性质及岩石圈减薄方式 总被引：14，自引：1，他引：14
薛家石梁杂岩体位于北京北山地区,在平面上呈北西向的椭圆状,主要由辉长岩、二长辉长岩、二长岩、正长岩和花岗岩组成。根据锆石SHRI MP定年结果为132·8~123·3Ma,形成于早白垩世早期。野外地质特征、矿物学特征、岩石学特征及地球化学特征表明,薛家石梁杂岩体中二长岩是二长辉长岩岩浆与正长岩岩浆混合作用的产物,从辉长岩岩浆到二长辉长岩岩浆经历了结晶分异作用。薛家石梁杂岩体中正长岩具高Sr,低Y及Eu正异常特征,推测其可能来源于加厚陆壳的底部。薛家石梁杂岩体中辉长岩中Mg#值为65,w(Nb)/w(U)值为37·8,这些特征暗示其可能为原生岩浆。辉长岩中ε(Nd)值为-6·5,表明其源区岩石不具亏损地幔特征;而辉长岩具富集Pb、Ti、Nb正异常,Hf的负异常,与EMI型富集地幔特征(具Nb、Hf正异常及Pb的负异常)不一致;辉长岩中Rb、Th、Nb、U、La、Ce元素含量比EMI型富集地幔低一个数量级;杂岩体中N(87Sr)/N(86Sr)与N(206Pb)/N(204Pb)值具正相关关系也表明不具交代富集型地幔特征。因此,我们认为辉长岩岩浆源区应为软流圈地幔,而不是富集型地幔(EMI)。辉长岩中ε(Nd)的负值是辉长岩岩浆与太古宙下地壳相互作用的结果。因此,我们认为中国东部岩石圈减薄的主要机制是岩石圈的拆沉作用。 相似文献