利用定量矿物再造法恢复阜平群的原岩性质——介绍一种原岩恢复的新方法

恢复变质岩石的原岩性质,是在变质岩地区从事地质填图、矿产普查和勘探工作时所面临的重要而又困难的工作。目前人们利用野外地质产状、变余结构构造、岩石化学、地球化学、同位素地质学、副矿物等多种方法和手段来探讨这一问题,其中的一些方法已被广泛利用,有些方法在国内已有介绍。本文以阜平群为例介绍苏联学者鲁金科(В.Е.РУДЕНКО)等提出的定量矿物再造法。     

蚀变岩石的化学成分与原岩恢复的讨论

岩石化学是研究各种地质过程的本质联系和演化规律的重要手段与方法.据国外统计,1841～1913年,全世界完成火成岩分析11024件,加拿大地质调查所1846～1954年分析了1300件,1954～64年分析了6200件,美国1966～68年平均每年分析2800件.随着我国地质科学的迅速发展,对岩石化学分析的要求与日俱增.本文着重讨论蚀变对岩石化学研究的影响.一要求与现状根据岩石学上的要求,在选择岩石化学资料时必须考虑:(1)岩石学的研究程度,样品的岩石名称、岩性及岩相划分、产     

全国变质岩原岩恢复学术讨论会在烟台召开

由本会变质岩专业委员会和中国地质学会岩石专业委员会、山东省地质学会联合举办的全国变质岩原岩恢复学术讨论会,于1983年11月1日至7日在山东省烟台市召开。到会代表118人,分属22个省市的72个单位。会议共收到论文摘要126篇,论文65篇。内容包括变质岩原岩恢复的综合方法,各种岩石化学计算法、微量元素法、多种副矿物法、数学地质法、稀土地球化学法以及氧     

对17种恢复变质岩原岩的岩石化学方法的检验结果

在变质岩研究的领域里,恢复变质前原岩的问题愈来愈显得重要了。恢复变质岩原岩的方法很多,有岩石矿物方法,岩石化学方法,地球化学方法等。其中岩石化学方法在目前来说是比较成熟的,而且适用范围也比较广泛。在国内外有关资料中,常见的恢复变质岩原岩的岩石化学方法有数十种之多。这些方法是不同的地质学者,依据不同地区的岩石化学资料,针对不同的问题而提出来的,因而其可靠程度及适用范围自然是不相同的。这样就会在选用恢复变质岩原岩的岩石化学方法时无所适从。常常有人认为多用一些方法互相比较,效果可能会好一些,其     

根据共生矿物-定量分析恢复变质和交代蚀变岩石的原岩

当前,恢复变质岩原始成分的各种岩石化学方法颇为流行.这些方法都是以变质作用过程中岩石总化学成份或其个别组分不发生变化的原则为基础的.在查明带状变质杂岩发育区的地质特征时有必要运用这些方法.但困难在于,许多情况下用这些方法不可能恢复混合成分的岩石和在非等化学条件下蚀变的岩石.为此,作者提出了定量-矿物恢复法(KMP法).它的基本前提是:1)在非等化学变质作用和交代作用情况下,几乎总保留有残余区段,对其进行研究可以获得岩石原始成分的信息;2)对于正常的"等化学"变质作用,变质矿物共生组合含量与岩石的原始化学成分有一定关系.     

多元统计分析方法在变质原岩恢复工作中的应用

众所周知,变质作用前后岩石的常量化学组织分相对含量被认为是不变的,虽然在不同性质和强度变质作用下,出现地矿物组合比较复杂,仍可利用它的含量与未变质的标准原岩进行类比,从而对变质原岩进行有效的判断。保、尼格里(Poul Niggl)是最早利用岩石化学方法恢复变质原岩成份的学者之一。他和一些人认为:岩石中具最大平     

用岩石总基度和CIPW标准分子恢复变质岩原岩

用岩石总基度和ＣＩＰＷ标准分子恢复变质岩原岩林文蔚（中国地质科学院矿床所，北京１０００３７）关键词变质岩，原岩恢复，岩石总基度，ＣＩＰＷ标准分子变质原岩恢复对变质地质的研究有着重要的意义。迄今，人们从岩体地质、岩相学、元素地球化学、同位素地质等诸多侧...     

太古界太华群变质原岩性质的恢复

太古界太华群为华北地台南缘出露的最深“结构层”。阜平期是影响深刻的变质作用期,使太华群矿物成分、岩石组构均发生了强烈的改造,达到角闪岩相—麻粒岩相,混合岩化较为强烈,属低压相系的变质作用。由于对它的研究可以了解地壳早期的演化特征,加之其中产有金、铁、铅、锌等多种矿产,历来为地质工作者们所重视。本文从地质学、岩相学(或矿物、岩石学)、岩石化学和地球化学等方面对其原岩性质进行恢复。有错之处,请批评指正。     

赣东南寻乌岩组原岩恢复及其时代问题的讨论

赣南前震旦纪地层的存在与否一直存有争议。利用岩石化学和稀土元素地球化学方法对赣东南会昌－寻乌一带的寻乌岩组变质岩系进行原岩恢复,并与区内震旦、寒武系及邻区闽西南中元古代桃溪岩组成比,结果表明,区内寻乌岩组与震旦、寒武系在岩石地球化学及稀土结球化学特征上具有显著差别,二者具有不同的原岩类型,形成于不同的构造古地理沉积环境;而与桃溪岩组具有相似的岩石和稀土元素地球化学特征,二者具有相同的原岩类型,形成于类似的构造古地理沉积环境,寻乌岩组原时代属前震旦纪。     

应用岩石化学方法恢复变质岩原岩类型的一些问题

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。     

Reactive infiltration instability of a granitization front during the generation and development of granite-gneiss domes

The origin of granite-gneiss domes is traditionally attributed to gravity tectonics, the ascent of granite-gneiss diapirs in a gravitational field owing to a relative decrease in the density of granitized rocks compared with their protolith. This is usually considered by the example of a two-layer medium with a lower layer of granitized rocks overlain by a denser protolith layer; the development of gravitational instability in the system results in the ascent of a granite-gneiss diapir. However, the diapiric process can be initiated only if Archimedes?? buoyancy forces at the roof of the granite-gneiss layer will overcome the resistance of the protolith rocks related to their long-term strength. Under the conditions of plastic deformations, this requires the existence of a large-scale irregularity in the relief of the layer boundary, namely, an antiform cusp in the roof of the granite-gneiss layer. The model is based on the assumption that such antiforms appear owing to the reactive infiltration instability of the morphology of the granitization front caused by an increase in the fluid permeability of granitized rocks compared with that of the protolith. The results of computer modeling support the geological feasibility of the reactive infiltration mechanism of the generation and development of the protodiapiric forms of the granitization front triggering the development of the diapiric process of the gravitational upwelling of granite-gneiss domes. The model of a protodiapir stage allows us to consider dome formation as a result of the development of two sequential instabilities: the reactive infiltration instability of the granitization front related to an increase in the permeability of the transformed rock followed by the gravitational instability related to a relative decrease in rock density.     

青藏高原北部可可西里狮头山含硬玉岩类的基本特征及地质意义

描述了可可西里山南狮头山含硬玉岩类的岩石学、矿物学特征。含硬玉岩类的原岩为辉长岩，围岩为石炭—二叠系。由于变质作用不彻底，保留有原岩的矿物组合。典型的高压变质矿物组合为：钠长石 硬玉 霓石 蓝闪石 绿帘石 绿泥石。硬玉SiO2、FeO偏低，Al2O3、Na2O明显偏高，变质矿物组合中以富钠矿物为主，缺少石英，与国内外含硬玉岩类的原岩成分、变质矿物组合均不相同，是一种新的高压低温硬玉岩类。狮头山高压变质带向西延至若拉岗日、大横山一带，与北侧的西金乌兰—金沙江板块缝合带(西段)平行产出，以此推测缝合带南侧的羌北—昌都板块向北消减于巴颜喀拉板块之下。     

Initial Mineral Composition and Geochemical Signature of High-Alumina Gneisses in the Chupa Formation of the Belomorian Group,the Baltic Shield

The normative mineral composition of protolith for high-alumina gneisses in the Chupa Formation of the Belomorian Group (Baltic Shield) is presented. Based on protolith composition, index of maturity or chemical index of alteration (CIA), localization of data points of gneisses on discriminant diagrams, and several index ratios, it is suggested that the protolith of the studied rocks was composed of low-mature sediments (graywackes). The material delivered to the sedimentary paleobasin was derived from ultramafic, mafic, and intermediate rocks. Correlation between some elements (Rb versus K₂O, Ti and Ga versus Al, and Sr versus smectitic clay and plagioclase), typical of Phanerozoic sedimentary rocks, is also revealed in the studied gneisses.     

山西原平王家庄条带状磁铁石英岩矿床元素地球化学特征及其地质意义

山西原平王家庄铁矿床为五台山地区产出的条带状铁建造（BIF）的典型代表。含矿岩石为磁铁石英岩,围岩主要为斜长角闪岩、角闪变粒岩、石英片岩等。通过对变质岩的原岩恢复,得出其原岩主要为火山岩,具有从拉斑玄武岩向钙碱性火山岩演化的特点,局部有陆源碎屑的加入。微量元素中相对亏损Ta、Nb、Zr、Ti等高场强元素,相对富集K、Rb等大离子亲石元素,具有较低的w(Y)/w(Nb)比值,表明本区处于岛弧和活动大陆边缘带的构造环境。磁铁石英岩的稀土元素配分型式为向右缓倾斜的轻稀土富集型,具轻微铕正异常和轻微铈负异常,稀土元素特征表明BIF形成于典型的海洋环境,早太古代洋壳俯冲产出的高温气水热液对于BIF的沉积发挥了重要的作用。Eu轻微正异常说明本区火山活动较弱,海底高温热液对BIF的沉积贡献相对较少。BIF与其围岩在原始地幔标准化不相容元素蛛网图中的相关性说明二者有相同或相似的物质来源和成岩环境,二者同属一个沉积盆地,但却有不同的沉积过程和形成条件。     

Nd isotopic evidence for the position of southernmost Indian terranes within East Gondwana

Sm-Nd model ages of orthopyroxene-bearing massif charnockites from the Cardamom Hills Massif and adjoining supracrustal rocks from the Kerala Khondalite Belt in southernmost India are used to infer some of the relationships within these rocks and between them and neighboring areas. Most of these rocks have model ages of 2.1–2.8 Ga with most charnockites in the range 2.2–2.6 Ga. Thus, 3.0–3.4 Ga Archean rocks to their north did not contribute material to either suite and the two suites may have been juxtaposed after formation of the supracrustal rocks. The similarity of Sm-Nd isotope systems in the two units studied here supports an argument that the massif charnockites were the primary sole source of the detritus incorporated into the supracrustal rocks. A cordierite gneiss, representative of a relatively minor lithology in the supracrustal belt, has a model age of 1.3 Ga. The protolith of this gneiss not only formed from much younger material than the rest of the belt but also formed significantly after the other metasedimentary rocks. The source material of the gneiss protolith may have been located in the Wanni and Vijayan Complexes of Sri Lanka. The overlap of the model ages of rocks in this area and those in the Highland Complex of Sri Lanka supports the notion that these two sets of rocks were joined to each other in Gondwana. They belong to a belt that ran from Antarctica through Sri Lanka and India into Madagascar. This belt was involved in Pan-African tectono-metamorphism, as reflected in the 550 Ma age of the last, granulite-forming, event throughout the belt.     

常用剥蚀厚度恢复法在东营凹陷南坡西部“红层”的应用

东营凹陷南坡西部是指东营凹陷南坡石村断层以西的部分,孔店期—沙四早期沉积主要是以红色陆相碎屑岩为主的地层,即为通常所说的"红层"。受后期构造活动的影响,沙四下—孔一地层遭受不同程度的剥蚀,根据剥蚀厚度恢复方法的应用结果及适用性分析认为:厚度趋势法主要用于对剥蚀厚度区间和剥蚀范围进行标定,选用泥岩声波时差法和沉积速率比值法对剥蚀厚度数值的区间进行厘定。在凸起区及纯化构造带"红层"顶部削截明显区可直接使用厚度趋势法;靠近林南断层上升盘和高青平南断层上升盘的区域,选用声波时差法恢复"红层"顶部剥蚀厚度的效果好于其他构造带;平方王潜山构造带优选沉积速率法恢复"红层"尤其是沙四下亚段剥蚀厚度;优化的孔隙度法适合对孔隙度较大凸起区的沙四下亚段剥蚀厚度进行较为准确的标定;包裹体测温法和镜质体反射率法的恢复结果为少数单井数据点,仅作为参考。     

MATLAB在碎屑沉积岩矿物含量计算中的应用

岩石学与地球化学研究中,岩石中矿物含量的确定是一项重要的基础工作,传统测定主要依赖偏光显微镜镜下观察统计或进行编程计算,效率较低。通过实例介绍了使用MATLAB工具箱中非负线性最小二乘法根据岩石化学与镜下观察到的矿物种类对碎屑沉积岩中矿物含量进行定量计算的应用。计算结果表明,使用这种计算方法对岩石矿物含量的计算结果明显比显微镜下统计的更准确、快速,值得推广应用。在使用同时,也要注意合适的矿物化学组成的正确选取,以保证计算的真实有效。     

Characteristics of Compositional Migration in Mylonites from the Ductile Shear Zones of the Southern Tancheng-Lujiang Fault Belt, Eastern Anhui Province

On the basis of field geology, three typical ductile shear zones in the southern part of the Tancheng-Lujiang fault belt have been chosen for a detailed study. Altogether ten samples of the tectonites have been collected for this study. The paper is focused on a comprehensive study of the tectonites in the medium-lower horizons of the ductile shear zones. The mineral compositions of the rocks are analyzed with EPMA and some typical whole-rock samples analyzed by chemical and ICP methods. Based on the comprehensive study of the characteristics of the deformation, the mineral assemblages and the changes of chemical composition of the bulk rocks, this paper presents a discussion on the relationship between the volume loss, the fluid flow and compositional changes during mylonitization of the ductile shear zones in this region. Our study shows that there are a large amount of fluids flowing through the shear zones during the process of mylonization, accompanied by the loss of rock volume and migration of el     

Behaviour of boron in the generation of an anatectic complex: The Pen˜a Negra complex, central Spain

The Pe˜na Negra anatectic complex (central Spain) was formed from a pelitic protolith low in boron (3–80 ppm), by dehydration reactions, melting and fluid loss, which expelled much of the boron; residual B is present in sillimanite and muscovite. Migmatite melanosomes and restites (sillimanite + biotite + ilmenite) are relatively richer in B (mean 29 ppm), while the leucosomes are poorer (13 ppm). Late shears, fractures and zones of retrograde alteration have permitted some reintroduction of B. Experiments demonstrated that B cannot be removed from these rocks by heating or by leaching, indicating that very little is present in superficial adsorption and that the element occurs in mineral structures.     

碳酸盐岩中碳酸盐矿物稀土元素分析方法进展

碳酸盐岩中测定碳酸盐矿物的稀土元素主要有酸溶-ICP-MS和LA-ICP-MS方法.酸溶-ICP-MS方法用盐酸、硝酸溶解碳酸盐矿物,但也能溶解部分非碳酸盐矿物,而影响分析结果;用醋酸溶样可避免非碳酸盐矿物的干扰,但可能没有溶样完全,同样影响分析结果.LA-ICP-MS是应用激光对碳酸盐矿物进行原位剥蚀,将蒸发物导入ICP-MS进行分析,对不合粘土等的碳酸盐矿物最有效,由于激光束光斑较大,且碳酸盐岩中普遍含有微小的粘土矿物,可能也存在不确定性.总体而言,酸溶-ICP-MS和LA-ICP-MS获得的稀土元素页岩标准化配分模式及主要参数相似,均可用于沉积环境的示踪.