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在变质岩的研究工作中,恢复各种变质岩的原岩性质是研究变质岩系的原岩建造和形成环境、进行地层划分和寻找有关矿床的基础。在国内外研究变质岩原岩性质的工作中,应用岩石化学的方法十分普遍,特别是对那些产状特征不明显和原岩组构已经消失的深变质岩石尤为重要。由于编制中国变质图的需要,笔者根据已有资料,对目前国内外常用的三十几种岩石化学方法的特点及其应用情况进行了分析研究,现就有关问题提出一些看法供大家讨论。 相似文献
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恢复变质岩原岩的性质是研究变质岩的重要课题。恢复变质岩原岩性质的方法很多,目前普遍采用的是岩石化学法和地球化学法。由于岩石的化学成分变化很大,有些沉积岩的成分与火成岩的成分很相似,变质产物也很相似,特别是那些经过非等化学的深变质的岩石,有的本来是副变质岩,却投影在正变质岩的区域内,或落在模稜两可的地区。目前,有人利用岩石中物理化学性质稳定的锆石区分正副变质岩。 相似文献
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平潭—南澳变质岩带的Sm—Nd年代学研究及其大地构造意义 总被引:8,自引:0,他引:8
福建东南沿海变质岩的原岩时代长期未获解决。笔者采用 Sm-Nd 年代学技术,结合古生物成果,证明变质岩原岩时代为早古生代。在此基础上划分出平潭-南澳褶皱带并讨论其大地构造性质和意义。 相似文献
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判别变质岩的原岩性质的方法较多,本文只介绍用尼格里值编成图解,籍以判别变质岩原岩性质的有关方法及计算尼格里值的程序。众所周知,用常规方法计算尼格里值较为烦琐。为此,笔者特将其计算方法用袖珍电子计算器编成程序,这样便可尽快而准确的获得所需的尼格里值。 相似文献
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火山岩岩石化学,地球化学数据库管理系统及应用程序 总被引:1,自引:0,他引:1
在微机上用dBASEⅢ建立了火山岩岩石化学、地球化学数据库管理系统;开发了应用程序。火山岩数据库包括岩石描述、主要氧化物含量、稀土元素含量、其他微量元素含量、同位素分析、矿物分析等六个子库,可以存贮二百余项有关火山岩的数据和信息。数据库管理系统具有建立数据库结构、数据维护、数据输出、应用程序接口及退出系统等项功能。操作简便,易于掌握。应用程序主要包括岩石化学、地球化学和数理统计等计算程序,各种地球化学图件的绘图程序。火山岩数据库及其管理系统和应用程序为火山岩岩石化学、地球化学的综合研究提供了一种方便、实用和有效的手段。 相似文献
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贾福聚念红良高建国郭跃进燕永锋 《地质科学》2017,(3):837-854
夕卡岩是滇东南老君山成矿区众多锡多金属矿床的主要赋矿围岩。本文在系统分析了夕卡岩的产状特征和矿物组成特征的基础上,采用岩石化学和微观结构、构造相结合的方法,进行了原岩恢复。认为该类夕卡岩的原岩中含有大量中-基性火山岩,其形成过程与海相火山活动有关。滇东南地区寒武纪为大陆边缘拗陷盆地构造环境,含矿夕卡岩微量元素组成特征与火山弧玄武岩类似,推测研究区在早加里东期区域拉张作用背景下,盆地地壳变薄导了混杂作用,最终在拗陷盆地中心形成海相中-基性火山喷发及成矿作用。研究区中、下寒武统均有火山喷流沉积岩分布,反映了该区海相火山活动的多期次性。该套含矿夕卡岩为火山喷流沉积岩与其它正常海相沉积物混杂后,经印支期区域变质作用形成。 相似文献
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CIPW标准矿物计算法应用时存在问题的探讨 总被引:1,自引:0,他引:1
CIPW法是当今最广泛应用的岩石化学计算法之一,其目的在于提供模拟矿物成分和相对数量,为岩石正确命名提供依据.作者在应用CIPW法过程中,发现不同教科书上的计算原理及方法存在差异,给实际应用造成不便;本文就斜长石牌号的计算方法、CIPW计算原理以及钠长石分配方法等问题进行了探讨. 相似文献
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本文叙述了吉林省柳河县双河堡铬铁矿的地质特征,并对矿床的成因进行了初步探讨。根据岩石化学成分特点,原岩应为基性,超基性岩分异、熔离作用产物,后经变质改造形成滑石岩,阳起-透闪岩等岩石组合,其成因类型应为岩浆分异-熔离型矿床。 相似文献
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递增变质作用过程中化学元素的演化规律———以山西五台群变质同位地层为例 总被引:1,自引:0,他引:1
山西五台群文溪组和柏枝岩组岩石学特征和岩石化学、微量元素及稀土元素特征研究表明,这两个组中相应层位地球化学特征基本一致。递增变质作用使岩石贫Na2O、K2O及大离子亲石元素和相对富集FeO、MgO及铁族元素。由于变质作用仅使稀土元素总量发生微小变化,而不改变其总体分布型式,所以稀土元素是指示岩石形成与演化的良好指示剂 相似文献
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J. M. Ferry 《Contributions to Mineralogy and Petrology》1982,80(1):59-72
Whole-rock major element chemical analyses of progressively metamorphosed impure carbonate rocks and pelitic schists, collected from the same metamorphic terrain, reveal similarities and differences in the chemical response of these rock types to the metamorphic event. Relative to a constant aluminum reference frame, both schist and carbonate exhibit no detectable change in their contents of Fe, Mg, Ti, Si, and Ca with change in metamorphic grade. Carbonate rocks become progressively depleted in K and Na with increasing grade of metamorphism, while schists exhibit no statistically significant change in their contents of K and Na. Both rock types become depleted in volatiles (principally CO2 and H2O) with increasing grade.Whole-rock chemical data permit two mechanisms for migration of K and Na from the carbonate rocks during metamorphism: (a) diffusion of alkalis from carbonate to adjacent schist; (b) transport of alkalis by through-flowing metamorphic fluid (infiltration). Mineral equilibria in schist and metacarbonate rock from the same outcrops allow calculation of the affinity for cation exchange between the two rock types during metamorphism. Measured affinities indicate that if mass transport of K and Na occurred by diffusion, chemical potential gradients would have driven the alkalis from schist into carbonate rock. Because diffusion cannot produce the observed chemical trends in the metacarbonates, K and Na are believed to have been removed during metamorphism by infiltration.The disparity in chemical behavior between the pelitic schists and metacarbonate rocks may be a result of enhanced fluid flow through the carbonates. The carbonate rocks may have acted as metamorphic aquifers; the greater flow of fluid through them would then have had a correspondingly greater effect on their whole-rock chemistry. 相似文献
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粤北澜河变质岩的地球化学特征及其地质意义 总被引:1,自引:0,他引:1
粤北澜河变质岩主要由黑云母变粒岩和白云母绿泥片岩组成。根据主要元素、微量元素与稀土元素组成以及在各种相关判别图解上的投影,黑云母变粒岩的原岩为砂质岩,白云母绿泥片岩的原岩为泥质岩,它们主要是在被动大陆边缘的沉积环境中形成。根据黑云母变粒岩中单颗粒碎屑锆石最小U—Pb年龄为725Ma以及加里东期或早于加里东期变质的事实,原岩的沉积时间为早古生代。澜河变质岩的Sm—Nd同位素组成表明,它们的物源区为古元古代地壳,形成过程中没有年轻地壳物质加入。 相似文献
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W.U. Reimold 《Geochimica et cosmochimica acta》1982,46(7):1203-1225
Impact melt lithologies of the 77 m.y. old Finnish meteorite crater Lappajärvi as well as the Precambrian target rocks have been studied in detail, to identify and characterize different impact melt types (clast-poor, clast-rich, suevitic melt) and to study their chemical (major and trace elements) and isotopic (Rb-Sr) compositions in comparison to the composition of the target rocks.The Rb-Sr system of the whole melt body—including the suevitic melt—is shown to have been reequilibrated by the impact by extensive turbulent mixing of the various melted or vaporized target rocks. Chemical interactions (exchange of alkali elements, 87Sr-redistribution) between feldspar clasts and impact melt surrounding them are the result of thermal metamorphism following the incorporation of target rock fragments of various degrees of shock metamorphism into the superheated melt. Exchange reactions between clasts and melt are determined by thermal activation, but the degree of shock metamorphism in the clasts plays an important role, too.Major and trace element distributions in impact melt and basement rocks indicate that the Lappajärvi melt body chemically is extremely homogeneous. Even volatile elements (such as Zn and Cu) were not strongly fractionated. Comparison of the abundances of siderophile elements in the impact melt (e.g., 118–177 ppm Cr, 195–340 ppm Ni, 6–12 ppb Ir) and calculated target rock mixture (79% mica schist, 11% granite-pegmatite, 10% amphibolite) (e.g., 85.6 ppm Cr, 54.8 ppm Ni, 0.5 ppb Ir) revealed the chondritic nature (C or H chondritic) of the meteoritic projectile. Less than 2% of the meteorite can be detected in the coherent melt, whereas the suevitic melt is uncontaminated by the projectile. 相似文献
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Newly developed evidence for the original Tethysan island-arc volcanic rocks in the southern segment of the South Lancangjiang Belt 总被引:1,自引:0,他引:1
This paper re-describes the characteristics of pre-Ordovician (Pt3) metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province from the aspects of petrographic characteristics, rock assemblage, petrochemistry, REE, trace elements, lead isotopes and geotectonic setting. The metamorphic volcanic rocks maintain blasto-intergranular and blasto-andesitic textures; the volcanic rocks are characterized by a basalt-andesite-dacite assemblage; the volcanic rocks are basic-intermediate-intermediate-acid in chemical composition, belonging to semi-alkaline rocks, with calc-alkaline series and tholeiite series coexisting, and they are characterized by low TiO2 contents; their REE distribution patterns are of the LREE-enrichment right-inclined type; the volcanic rocks are enriched in large cation elements and commonly enriched in Th and partly depleted in Ti, Cr and P, belonging to the Gondwana type as viewed from their Pb isotopic composition; petrochemically the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the region studied. 相似文献