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西藏曲水岩基的Pb、Sr同位素组成及其三元混合成因模式 总被引：7，自引：0，他引：7
本文综合分析了西藏曲水岩基的Pb、Sr同位素组成特征，并运用同位素的混合模式对该岩基的物质来源和成因进行了进一步的深入研究。结果表明，该岩基的Pb、Sr同位素组成较好地符合三元混合模式。结合冈底斯岩带的地质、构造及其他地球化学特征，得出曲水岩基花岗岩类岩石的物质来源包括幔源岩浆、前造山带和上地壳物质三部分。 相似文献
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本文从火山机构的组成地层,空间形态,岩相特征和岩石特征,论述了满杖子破火山地质特征,分析了火山岩岩石化学,微量元素和稀土 球化学特征。 相似文献
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张金接 《水文地质工程地质》1992,19(3):55-58,48
本文通过大量工程实例的总结,指出岩体裂隙几何特征决定了灌浆材料对裂隙的灌入性能,从而影响帷幕的灌浆标准,建议在确定具体工程的帷幕灌浆标准时应考虑地基的地质条件,并结合拟采用的灌浆方法来进行,对一般地层常规水泥灌浆方法可达到现行的规范标准,高压灌浆、化学灌浆、超细水泥灌浆均是解决低透水性岩基灌浆的有效途径。 相似文献
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东营凹陷下第三系流体-岩石相互作用研究 总被引：38，自引：5，他引：33
盆地内地层流体-岩石相互作用导致储层特征和流体性质发生变化,影响油气藏的形成与分布。本文分析了东营凹陷下第三系地层孔隙流体的化学和动力学特征及其分布规律,根据地层中矿物的组成和结构特征对成岩过程中地层古流体的地球化学特征进行了推测。并通过对典型油田泥岩层和砂岩层中矿物组合及其在地层剖面上的变化规律的实例剖析,揭示了东营凹陷下第三系储层中流体-岩石相互作用的基本特点,在此基础上,建立储层中流体-岩石相互作用的地质/地球化学模型。 相似文献
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从地质异常的角度,重点分析了大冶—九瑞地区主要地质异常的特征及其对成矿的影响．由分析可知：基底断裂异常控制了本区若干重要规模较大的隐伏岩基及伴生矿田,而盖层构造异常控制铜金矿床和铁铜矿床的空间位置;地层的地球化学异常和岩相古地理异常是造成一些铜金矿床层控性的主要地质因素;盖层的岩性异常为含矿热液的渗流、循环、聚集和矿质沉淀等一系列成矿作用提供了有利的物理和化学条件;中生代岩浆岩的异常活动期也是本区主要的铁铜成矿期,岩浆岩系统的多层分枝和分带性结构控制了本区成矿系统的三维空间分布．在上述分析的基础上,构置了地质组合熵作为反映控矿地质因素组合系统结构复杂程度的综合变量,并圈定出组合熵异常,由此确定了综合地质异常与矿床的关系． 相似文献
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碳同位素与早元古代地层对比 总被引：2，自引：0，他引：2
本文首次较详细地研究了早元古代碳酸盐地层的碳同位素组成，样品采自华北早元古代标准地层单元──山西五台地区滹沱群，结果表明碳同位素组成随地质时代有明显的变化，并与地层层位有很好的对应关系。作者认为，碳同位素对于早元古代碳酸盐地层的对比是很有用的。 相似文献
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本文按照将成矿的地质环境与因素转化为地球化学的环境与因素,进而再把控矿的地球化学环境标志转化为地球化学找矿指标的思路,通过系统的地质-地球化学研究证明陕南柞水水阳成矿带菱铁矿铅、银、锌矿床上要是海底热卤水同生沉积成困,矿床受相对封闭的海底洼地和同生断裂构造的控制。但在普查阶段同生断裂与海底洼地是很难从地质上确定的,因此设想应用反映热卤水高盐度的地球化学环境标志(粘土岩类高的硼和钡含量)来代替地质环境因素指示成矿有利地段。经近矿与远矿含矿地层(主要由粘土岩组成)硼和钡含量对比,肯定了上述设想,选择黑沟矿区进行硼量和钡量测量,结果在已知矿段圈出规模较大形态规整的硼和钡异常。研究表明,沉积地层中硼和钡的分布不仅可以很好地反映同生沉积成矿的高盐度环境,而且也是该类层控矿床找矿的有效标志。 相似文献
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Antonio Castro 《地学前缘(英文版)》2014,5(1):63-75
Granitod batholiths of I-type features(mostly granodiorites and tonalites),and particularly those forming the large plutonic associations of active continental margins and intracontinental collisional belts,represent the most outstanding magmatic episodes occurred in the continental crust.The origin of magmas,however,remains controversial.The application of principles from phase equilibria is crucial to understand the problem of granitoid magma generation.An adequate comparison between rock compositions and experimental liquids has been addressed by using a projected compositional space in the plane F(Fe t Mg)eAnorthiteeOrthoclase.Many calc-alkaline granitoid trends can be considered cotectic liquids.Assimilation of country rocks and other not-cotectic processes are identifed in the projected diagram.The identifcation of cotectic patterns in batholith implies high temperatures of magma segregation and fractionation(or partial melting)from an intermediate(andesitic)source.The comparison of batholiths with lower crust granulites,in terms of major-element geochemistry,yields that both represent liquids and solid residues respectively from a common andesitic system.This is compatible with magmas being formed by melting,and eventual reaction with the peridotite mantle,of subducted mélanges that are fnally relaminated as magmas to the lower crust.Thus,the off-crust generation of granitoids batholiths constitutes a new paradigm in which important geological implications can be satisfactorily explained.Geochemical features of Cordilleran-type batholiths are totally compatible with this new conception. 相似文献
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根据各花岗岩体地质构造特征、有关的热物理参数及主体花岗岩的放射性元素含量,采用简化的立方体数学模型计 算得出:南岭地区8个花岗岩基侵位后,其初始温度降低至结晶温度所需的时间(Δtcol)为3.9(金鸡岭)~5.5 Ma(九峰); 由于结晶潜热释放而使结晶过程延长的时间(ΔtL) 为2.6~3.5 Ma ;花岗岩浆侵位后产生的放射成因热使结晶过程延长的 时间(Δt A)为 5.2(陂头)~45.1 Ma(姑婆山) 。南岭地区 8 个燕山早期花岗岩基的侵位-结晶时差(△t ECTD)为 12.1(陂头) ~52.2 Ma(姑婆山), 结合锆石U-Pb年龄通过反演计算得出其侵位年龄 (tE ) 为194.4 (陂头)~219.3 Ma(九峰)。这为 南岭燕山早期花岗岩基属于印支期侵位提供了重要的岩浆动力学佐证, 揭示出近东西向展布的南岭晚中生代造山带具有印 支期构造格架(以侵位年龄为代表)和燕山早期花岗岩(以锆石 U-Pb 年龄为代表) 的双重特征。 相似文献
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碰撞造山带斑岩型矿床的深部约束机制 总被引：19，自引：8，他引：11
在印度-亚洲大陆碰撞过程中,俯冲板片断离触发了幔源岩浆底侵作用、下地壳部分熔融和冈底斯岩基带以及同岩基斑岩的产生.在此过程中,幔源岩浆分离结晶的产物、下地壳岩石部分熔融残余和地壳分异过程中下沉的镁铁质块体,构成了加厚下地壳.随着造山岩石圈的冷却和加厚下地壳重力不稳定性的增加,岩石圈拆沉作用触发了后碰撞斑岩型岩浆活动.与此相应,碰撞造山带斑岩型矿床可以形成于同碰撞和后碰撞两个不同的构造阶段.同碰撞成矿作用发生于岩基带形成时期,成矿物质主要来自于底侵幔源岩浆及更深部的含矿流体,其触发机制是俯冲板片的断离.后碰撞成矿作用发生于加厚下地壳冷却之后,成矿物质主要来自于新生矿源层和更深部的含矿流体,其触发机制为岩石圈拆沉作用.在同碰撞构造阶段,伴随着幔源岩浆的底侵作用,深部流体和幔源岩浆所含的成矿物质被注入到岩基岩浆中,与从岩基岩浆源区萃取的成矿物质汇聚在一起,一部分受岩基热的驱使上升成矿.由于流体中成矿元素的浓度强烈依赖于压力,另一部分成矿元素则滞留在难熔残余中形成新的矿源层.当发生岩石圈拆沉作用时,由此矿源层部分熔融形成的斑岩岩浆将相对富含成矿物质,导致碰撞造山带第二次成矿作用大爆发. 相似文献
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V. V. Yarmolyuk A. M. Kozlovsky V. M. Savatenkov V. P. Kovach I. K. Kozakov A. B. Kotov V. I. Lebedev G. Eenjin 《Petrology》2016,24(5):433-461
Data on the composition, inner structure, and magma sources of giant batholith in the Central Asian Orogenic Belt are analyzed with reference to the Khangai batholith. The Khangai batholith was emplaced in the Late Permian–Early Triassic (270–240 Ma) and is the largest accumulations (>150000 km2) of granite plutons in central Mongolia. The plutons are dominated by granites of normal alkalinity and contain subalkaline granites and more rare alkaline granites. The batholith is hosted in the Khangai zonal magmatic area, which consists of the batholith itself and surrounding rift zones. The zones are made up of bimodal basalt–trachyte–comendite (pantellerite) or basalt-dominated (alkaline basalt) volcanic associations, whose intrusive rocks are dominated by syenite and granite, granosyenite, and leucogranite. Both the batholith and the rift zones were produced within the time span of 270–240 Ma. Although the rocks composing the batholith and its rift surroundings are different, they are related through a broad spectrum of transitional varieties, which suggests that that the mantle and crustal melts could interact at various scale when the magmatic area was produced. A model is suggested to explain how the geological structure of the magmatic area and the composition of the magmatic associations that make up its various zones were controlled by the interaction between a mantle plume and the lithospheric folded area. The mantle melts emplaced into the lower crust are thought to not only have been heat sources and thus induced melting but also have predetermined the variable geochemical and isotopic characteristics of the granitoids. In the marginal portions of the zonal area, the activity of the mantle plume triggered rifting associated with bimodal and alkaline granite magmatism. The formation of giant batholiths was typical of the evolution of the active continental margin of the Siberian paleocontinent in the Late Paleozoic and Early Mesozoic: the Khangai, Angara–Vitim, and Khentei batholiths were formed in this area within a relatively brief time span between 300 and 190Ma. The batholiths share certain features: they consist of granitoids of a broad compositional range, from tonalite and plagiogranite to granosyenite and rare-metal granites; and the batholiths were produced in relation to rifting processes that also formed rift magmatic zones in the surroundings of the batholiths. The large-scale and unusual batholith-forming processes are thought to have occurred when the active continental margin of the Late Paleozoic Siberian continent overlapped a number of hotspots in the Paleo- Asian Ocean. This resulted in the origin of a giant anorogenic magmatic province, which included batholiths, flood-basalt areas in Tarim and Junggar, and the Central Asian Rift System. The batholiths are structural elements of the latter and components of the zonal magmatic areas. 相似文献
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In the Archaean Murchison Province of Western Australia, granitoid batholiths and plutons that intruded into the ca. 2.7–2.8
Ga and ca. 3.0 Ga greenstone belts can be divided into three major suites. Suite I is a ca. 2.69 Ga monzogranite-granodiorite
suite, which was derived from anatexis of old continental crust and occurs as syn-tectonic composite batholiths over the entire
province. Suite II is a trondhjemite-tonalite suite (termed I-type) derived from partial melting of subducted basaltic crust,
which intruded as syn- to late-tectonic plutons into the greenstone belts in the northeastern part of the province where most
of the major gold deposits are situated. One of the Suite II trondhjemite plutons has a Pb−Pb isochron age of 2641±36 Ma,
and one of the structurally youngest tonalite plutons has a minimum Pb−Pb isochron age of 2630.1±4.3 Ma. Suite III is a ca.
2.65–2.62 Ga A-type monzogranite-syenogranite suite which is most abundant in the largely unmineralised southwestern part
of the province. Gold deposits in the province are mostly hosted in brittle-ductile shear zones, and were formed at a late
stage in the history of metamorphism, deformation and granitoid emplacement. At one locality, mineralisation has been dated
at 2636.8±4.2 Ma through a pyritetitanite Pb−Pb isochron. Lead and Sr isotope studies of granitoids and gold deposits indicate
that, although most gold deposits have initial Pb isotope compositions most closely similar to those of Suite II intrusions,
both Suite I and Suite II intrusions or their source regions could have contributed solutes to the ore fluids. These preliminary
data suggest that gold mineralisation in the Murchison Province was temporally and spatially associated with Suite II I-type
granitoids in the northeastern part of the province. This association is consistent with the concept that Archaean gold mineralisation
was related to convergent-style tectonic settings, as generation of both Suite II I-type granitoids and hydrothermal ore fluids
could have been linked to the dehydration and partial fusion of subducted oceanic crust, and old sialic crust or its anatectic
products may also contribute solutes to the ore fluids. Integration of data from this study with other geological and radiogenic
isotope constraints in the Yilgarn Block argue against direct derivation of gold ore fluids from specific I-type granitoid
plutons, but favour a broad association with convergent tectonics and granitoid magmatism in the late Archaean. 相似文献
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五道岭组是黑龙江重要的与成矿关系密切的陆相火山岩地层,长期以来对它的地质时代存在不同认识.本文依据近几年新取得的同位素测年数据,结合与五道岭组紧密伴生的花岗岩类的时代研究,以及对五道岭组火山岩类与伴生花岗岩类的地球化学特征对比研究,提出五道岭组地层时代属于晚三叠世—早侏罗世的新认识.论述了五道岭组火山岩类、晚三叠世—早侏罗世花岗岩类和与前二者关系密切的钼矿是在大体相同的地质时代依次相继形成.较早的陆相火山喷发形成五道岭组火山岩地层,随后发生多阶段的花岗岩类侵入,而钼矿在同源岩浆演化到更晚阶段形成.五道岭组火山岩类和晚三叠世一早侏罗世花岗岩类具有相同的岩浆起源,它们分别是同源岩浆在不同演化阶段和不同深度的产物,因而在时空关系、岩石化学、微量元素、稀土配分和同位素组成等方面表现了明显的一致性.五道岭组地层与钼矿及花岗岩类的密切时空关系和成因联系可用于评价钼矿成矿远景区. 相似文献
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《International Geology Review》2012,54(10):1280-1299
The Pernambuco–Alagoas (PE–AL) Domain contains major granitic batholiths typified by a wide range of TDM model ages (Archaean to Neoproterozoic), reflecting the important role of quartzofeldspathic plutons attending the Brasiliano (Pan-African) Orogeny. U/Pb zircon data for eight syn- to post-collision to syn-transcurrent granitic intrusions of the PE–AL Domain allow the studied plutons to be divided into two groups: (1) granitoids with crystallization ages older than 600 Ma (Água Branca, Serra do Catú, Serra da Caiçara, and Mata Grande plutons) and (2) granitoids with ages of ca. 590 Ma (Correntes, Águas Belas, Viçosa, and Cachoeirinha plutons). The intrusions of group 1, except for the Mata Grande Pluton, all show Nd TDM model ages ranging from 1.5 to 1.2 Ga, whereas the granitoids from group 2 and the Mata Grande Pluton have Nd TDM model ages ranging from 2.2 to 1.7 Ga. The studied granitoids are in part high-K, calc-alkaline, shoshonitic, and in part transitional high-K calc-alkaline to alkaline in terms of their bulk chemistry. Volcanic arc signatures associated with the Palaeoproterozoic TDM model ages are interpreted as inherited from the source rocks. The oldest ages and higher Nd TDM model ages recorded in the granitoids intruded in the southwestern part of the PE–AL Domain suggest that these intrusions are associated with slab-tearing during convergence between the PE–AL and Sergipano domains. The investigated plutons are coeval with high-K granitoids intruded within the Transversal Zone Domain of Borborema Province and calc-alkaline granitoids of the Sergipano Domain. This suggests that these geologic realms belonged to the same crustal block during the Brasiliano Orogeny. However, such large volumes of high-K granitoids with crystallization ages older than 600 Ma are not recorded in the Sergipano and Transversal Zone domains, suggesting differences in the crustal evolution of these three areas. 相似文献