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1.
金沙江蛇绿岩带蛇纹岩中异剥钙榴岩的成因及意义 总被引：1，自引：1，他引：0
金沙江蛇绿岩带绒角蛇绿岩由超镁铁岩与异剥辉长岩岩脉组成,在蛇绿岩就位过程中,异剥辉长岩岩脉碎裂为不规则的岩块包裹于超镁铁岩中,形成超镁铁岩中的构造包体。经过交代蚀变作用,超镁铁岩形成蛇纹岩,异剥辉长岩形成异剥钙榴岩。异剥钙榴岩的形成是超镁铁岩蛇纹石化和异剥辉长岩中斜长石钙铝榴石化循环作用的结果,并与对蛇绿岩起过作用的构造运动有关系,是变形作用伴随交代作用的产物。绒角蛇绿岩中的异剥钙榴岩的发现,说明金沙江蛇绿岩带不存在榴辉岩,其变质相属葡萄石一绿泥石低温低压相．也说明金沙江蛇绿岩带是洋壳残片“冷侵入”的产物。 相似文献
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3.
中国西南天山昭苏县东德沟地幔楔环境的斜长角闪岩与蛇纹岩接触带中发现了异剥钙榴岩.按异剥钙榴岩化程度,可将研究的岩石分为三种类型:斜长角闪岩、异剥钙榴岩化斜长角闪岩和异剥钙榴岩,它们的矿物组合分别为:角闪石+中长石+石英+榍石+磷灰石±次透辉石;角闪石+钙长石+透辉石+斜黝帘石+绿泥石±方解石;斜黝帘石+钙铝榴石+透辉石+绿泥石+方解石.异剥钙榴岩化岩石的矿物化学及主量元素特征反映出交代流体中富Ca、Al.与洋底变质环境和俯冲带中发生的异剥钙榴岩化作用相比,此处的异剥钙榴岩化岩石中的流体有限.质量平衡计算也表明斜长角闪岩在富Ca、Al流体的交代下形成异剥钙榴岩,这一过程中,早期有Mg元素加入,而晚期异剥钙榴岩形成时,Mg又大量流失. 相似文献
4.
蛇绿岩套中超基性岩体的岩石组合:蛇纹岩、异剥钙榴岩和蛇绿碳酸岩——以西阿尔卑斯Zermatt-Saas蛇绿岩为例 总被引：2，自引：1，他引：2
蛇纹岩、异剥钙榴岩和蛇绿碳酸岩是蛇绿岩套中超基性单元特有的3类岩石组合,该套岩石组合的形成过程复杂,经历了从地幔岩浆结晶分异、洋脊变质作用改造和俯冲-仰冲构造过程,记录了从地幔岩浆侵位到造山带形成、演化的全程信息。蛇纹岩由方辉橄榄岩、二辉橄榄岩和纯橄岩通过水化和氧化过程而形成;异剥钙榴岩由含水石榴石、符山石、绿帘石族矿物、透辉石和绿泥石等含水和含钙的硅酸盐矿物组成,是由基性岩经历钙交代和水化作用而形成;蛇绿碳酸岩则由高度破碎变形的蛇纹岩角砾和碳酸岩基质(方解石、白云石或菱镁矿)共同组成,碳酸钙主要来自海水参与蛇纹岩化过程产生的富钙热液。阿尔卑斯西部的Zermatt-Saas蛇绿岩体中这3种岩石的组合研究表明:蛇纹岩化过程发生在大洋变质时期,超基性岩体在海水的作用下形成蛇纹岩。蛇纹岩化过程中释放出主要来自斜方辉石和单斜辉石的钙,与水共同作用交代超基性岩体中的基性岩脉,从而形成异剥钙榴岩。蛇绿碳酸岩形成于俯冲变质之前或俯冲变质的早期。这3类岩石一经形成,都经历了其后的叠加变质作用,进而表明Zermatt-Saas蛇绿岩经历了大洋变质、与俯冲、折返和抬升有关的高压变质和区域变质、绿片岩相变质和晚期热液变质作用的pT轨迹演化,代表着西阿尔卑斯从洋脊变质作用到俯? 相似文献
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冀北异剥钙榴岩的岩石学、地球化学及锆石SHRIMP年代学研究 总被引：1，自引：0，他引：1
对产于红旗营子群黑云斜长片麻岩或黑云斜长变粒岩之中的冀北异剥钙榴岩进行岩石学研究表明,其主要矿物成分有富钙石榴石、钠长石或钡冰长石以及角闪石等,另有少量异剥辉石(透辉石)残留,其形态多呈大小不等的透镜状或团块状.异剥钙榴岩的化学成分总体表现为SiO2(36.63%～44.46%)明显不饱和,富CaO(17.81%～27.78%)、FeO*(9.76%～18.36%)和贫MgO(O.77%～4.56%)的特征.异剥钙榴岩化作用除导致岩石的CaO升高而SiO2降低外,REE总量和某些不活动性微量元素(Zr,Hf,Nb,Ta,Y和V等)含量也相应增加,但REE配分模式变化太大.冀北异剥钙榴岩的原岩可能为蛇绿岩型畀剥辉长岩,经历过早期的钙交代和晚期的钡交代.前者以岩石中发育富钙石榴石为标志,后者则形成钡冰长石,是富钡流体交代钠长石的结果.冀北异剥钙榴岩的锆石SHRIMP年龄为396.4 Ma±5.3 Ma,代表异剥钙榴岩的形成时代 相似文献
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西天山异剥钙榴岩的地球化学研究 总被引：5，自引：4，他引：1
西天山长阿吾子的蛇绿混杂岩带的超基性岩及其伴生岩石异剥钙榴岩位于伊犁中天山板块和塔里木板块碰撞造山带。微量元素特征表明退变榴辉岩原岩成因与俯冲带环境有关。异剥钙榴岩中稀土元素和微量元素全面、大幅度降低,反映出来自于蛇纹岩化,作用于异剥钙榴岩化流体的强大的淋滤作用。因而异剥钙榴岩的稀土和微量元素特征都不能反映原始岩浆的特点,无法据此推断原始岩浆产生的大地构造环境。对退变榴辉岩的主元素和微量元素稀土元素的研究表明,长阿吾子异剥钙榴岩的原岩钙碱性玄武岩可能形成于俯冲上板片(SSZ)的岛弧环境。 相似文献
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祁连山地区镁铁——超镁铁岩的多样性 总被引：11，自引：1，他引：11
祁连山地区出露有不同类型的镁铁－超镁铁岩，包括蛇绿岩，阿拉斯加型岩体，橄榄岩－闪长岩型岩体以有产于北祁连西部的一种特殊的镁铁－超镁铁岩组合。不同的镁铁－超镁铁岩形成于一同的构造环境，蛇绿岩代表洋壳的残片，阿拉斯加型岩体产生岛弧或活动陆缘环境，橄榄岩一闪长岩体则是板块碰撞之后形成的，根据蛇绿岩与大致同时代的阿拉斯加型岩体产出的位置，推测在北祁连早古生代时存在向南的消减事件。 相似文献
8.
接触交代夕卡岩型矿床中石榴子石和辉石成分特点及其与矿化的关系 总被引：1，自引：0，他引：1
本文对中国十四个接触交代钙夕卡岩矿床和钙-镁夕卡岩矿床中的三百多个样品的石榴子石和辉石成分进行了电子探针分析。不同矿床类型的石榴子石和辉石成分代表着钙夕卡岩矿床的十个矿种(Fe、Fe-Cu、Pb-Zn、W、Sn、Sn-Mo-Bi-W、、W-Bi-Cu-Mo、Cu-Zn、Cu-Sn、W-Zn-Cu)和钙-镁夕卡岩矿床的三个矿种(Fe-Cu、Mo、Pb-Zn)。石榴子石和辉石成分变化范围大,大多数石榴子石是含锰铝榴石+铁铝榴石+镁铝榴石小于15％(摩尔百分数)的钙铝榴石-钙铁榴石固溶体;大多数辉石是含小于5％的锰钙辉石的透辉石-钙铁辉石固溶体。有些Pb-Zn钙-镁夕卡岩矿床中的辉石显示出Mn含量有所增加。只有Sn和W钙夕卡岩矿床及Pb-Zn钙-镁夕卡岩矿床含(Sps+Alm+Pyr)总量大于15％的石榴子石。石榴子石和辉石成分与夕卡岩矿床金属矿化类型之间有某些联系。 相似文献
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本文对贺根山、鲸鱼、东巧、罗布莎、玉石沟等地超镁铁岩中(L-C)蛇纹岩标本的氢、氧同位素组成进行了分析,其变化范围为:δD=-101—-146,δ~(18)O=1.0—7.5。产生蛇纹石化作用时平衡计算水的氢、氧同位素为:330℃时δD=-77—-122,δ~(18)O=1.4—7.9;200℃时δD=-67—-112,δ~(18)O=-1.3—5.2。根据大洋型(L-C)蛇纹岩和大陆蛇绿岩杂岩型(L-C)蛇纹岩的氢、氧同位素组成特征来看,本文所研究的蛇纹岩明显地属于大陆蛇绿岩杂岩型蛇纹岩。蛇纹石化时平衡计算水的氢、氧同位素特征表明水的成因类型为大气降水型地下水,而非大洋水。本文中超镁铁岩的蛇纹石化作用发生在超镁铁岩侵位于大陆壳之后,即超镁铁岩的蛇纹石化作用发生于大陆环境,而非大洋环境,而且超镁铁岩在侵位于陆壳之后的最初阶段应为新鲜的地幔岩石。 相似文献
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强亲铁元素与亲石元素具有不同的地球化学行为，因此能够从不同的角度为造山带中超镁铁岩的成因及演化提供重要信息。位于苏鲁造山带东北端的胶东海阳所超镁铁岩主要由橄榄岩和辉石岩组成，它们常以团块状赋存于花岗质片麻岩中。虽然前人对这些超镁铁岩已经开展大量岩石学研究，但关于其成因及构造属性仍存在较大争议。本文开展了海阳所超镁铁岩的全岩主微量元素、强亲铁元素及Re-Os同位素的分析工作，结果显示蛇纹石化橄榄岩具有较高的MgO和Fe2O3T含量，较低的Al2O3、TiO2和CaO含量，明显富集流体迁移元素（U、Pb），亏损高场强元素（Zr、Hf），强亲铁元素没有发生明显分异，但Ru显示正异常，表明海阳所蛇纹石化橄榄岩是经历了低-中等程度部分熔融及熔/流体交代作用影响的残余地幔橄榄岩。海阳所辉石岩的主量元素表现出明显的结晶分异特征，稀土元素较原始地幔富集，铂族元素（PGEs）含量较低且发生了明显的分异，表明辉石岩的地幔源区经历过高程度的部分熔融和硫化物的分离。海阳所蛇纹石化橄榄岩的Os同位素地球化学特征表现出大洋亲和性，与辉石岩不具有熔体-残留体的关系。由于该地区发育较深层次的韧性剪切带，蛇纹石化橄榄岩中的橄榄石与辉石表现出韧性变形的特征，同时有辉石岩侵入到橄榄岩的现象，表明该地区的蛇纹石化地幔橄榄岩与辉石岩既不同时，也不同源，因此，暗示了该套岩石组合可能形成于大洋核杂岩（OCC）与洋脊型蛇绿岩（MOR）堆晶岩交互发育环境。 相似文献
11.
Wan Pu 《《地质学报》英文版》1990,64(1):31-39
Most chrysotile deposits occur in ultramafic rocks of the ophiolite suite. The chrysotile deposits dis-cussed in the present paper were formed through metasomatism and infilling-crystallization in a continentalserpentinization environment after plate convergence, where ultramafic rocks were replaced byhydrothermal solutions consisting mainly of deep-circulating heated water derived from atmospheric precip-itation. The critical state for the formation of asbestos in ultramafic rock bodies might be reached bysuperposition of multiple stages of serpentinization. Favourable fracture systems and relatively stable geo-logical environment are important conditions for forming chrysotile deposits. Three subtypes of chrysotiledeposits could be formed in different tectonic settings and under different minerogenic geochemical condi-tions. 相似文献
12.
Rodingites were dredged from fracture zones of the equatorial Mid-Atlantic Ridge along with serpentinized ultramafics, and fresh and metamorphosed basalts and gabbroids. These rodingites were generated by a metasomatic process at low temperature involving an enrichment in lime and water, and a loss of silica and alkalis. The parent rocks were gabbronorites which intruded ultramafic material as it ascended from the upper mantle to its present location in the upper oceanic crust. The gabbronorites were probably altered to rodingites while they were still in the lower oceanic crust. Since the rodingitization process appears to be concomitant, complementary and simultaneous with the serpentinization of the host ultramafic rocks, we infer that the serpentinization process also took place in the deeper part of the oceanic crust. These two simultaneous metasomatic processes thus predate the major phase of tectonic events which uplifted these blocks as cold, solid diapiric emplacements of ultramafic material and accompanying rodingites to their present positions along lines of weakness expressed as fracture zones. 相似文献
13.
T.A. Abrajano N.C. Sturchio B.M. Kennedy G.L. Lyon K. Muehlenbachs J.K. Bohlke 《Applied Geochemistry》1990,5(5-6)
Methane-hydrogen gas seeps with mantle-like C and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the Zambales ophiolite, Philippines. New measurements of noble gas and 14C isotope abundances, rock/mixed-volatile equilibrium calculations, and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration. The gas seeps are produced in rock-dominated zones of serpentinization, and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization. 相似文献
14.
Subduction of serpentinised mantle transfers oxidised and hydrated mantle lithosphere into the Earth, with consequences for the oxidation state of sub-arc mantle and the genesis of arc-related ore deposits. The role of subducted serpentinised mantle lithosphere in earth system processes is uncertain because subduction fluxes are poorly constrained. Most subducted serpentinised mantle is serpentinised on the ocean floor settings. Yet this material is poorly represented in the literature because it is difficult to access. Large volumes of accessible serpentinite are available in ophiolite complexes, and most interpretations of subduction fluxes associated with ultramafic rocks are based on ophiolite studies. Seafloor and ophiolite serpentinisation can occur under different conditions, so it is necessary to assess if ophiolite serpentinites are a good proxy for seafloor serpentinites. Serpentinites sampled during ODP cruise 209 were compared with serpentinites from New Caledonia. The ODP209 serpentinites were serpentinised by modified seawater in a shallow hydrothermal seafloor setting. The New Caledonia serpentinites were serpentinised in a mantle wedge setting by slab-derived fluids, with possible contributions from oceanic serpentinisation and post-obduction serpentinisation. Petrological, whole rock and mineralogical analyses were combined to compare the two sample sets. Petrologically, the evolution of serpentinisation was close to identical in the two environments. However, more oxidised iron, Cl, S and C is present in serpentine from the ODP209 serpentinites relative to the New Caledonia serpentinites. Given these observations, the use of serpentinites from different geodynamic settings as a proxy for abyssal serpentinites from spreading settings must be undertaken with caution. 相似文献
15.
OCCURRENCE OF HIGH-PRESSURE RODINGITES IN THE OPHIOLITES OF INDUS SUTURE ZONE, EASTERN LADAKH,THE HIMALAYA:TECTONIC AND METALLOGENIC SIGNIFICANCE 相似文献
16.
Three varieties of alpine-type ultramafic rocks are distinguish in the Norwegian Caledonides associated Basal Gneiss Complex. Type one rocks have primary (magmatic) olivine, clinopyroxene, orthopyroxene and chromite, and are partly or completely serpentinised. They are found exclusively in rocks of Cambro-Silurian age. Type two are polymetamorphic metaperidotites or sagvandites consisting of olivine, enstatite and carbonate minerals, with talc and amphibole commonly being present. They are found in medium- to high-grade metamorphic rocks. Type three also show a metamorphic mineral association of olivine, orthopyroxene and minor chromite, while clinopyroxene, amphibole and chrome-bearing chlorite may also be present in some samples. Garnet may or may not occur and, where present, is often surrounded by reaction rims of spinel and amphibole. The type three ultramafic bodies are serpentinised to varying degrees and occur in high-grade metamorphic gneisses which may also contain eclogites and anorthosites. Distinction of these three varieties of ultramafic body may be useful for correlation purposes and for more detailed studies on the nature of their metamorphism. 相似文献
17.
藏南雅鲁藏布蛇绿岩被认为是新特提斯大洋岩石圈的残留。该带中段的日喀则白马让蛇绿岩是保存较完整的蛇绿岩岩块之一。该蛇绿岩主要由橄榄岩、蛇纹岩、镁铁质侵入岩和玄武岩组成,缺堆晶岩系。镁铁质侵入岩主要呈辉绿岩脉、岩床和少量的岩墙产出。辉绿岩脉在整个蛇绿岩层序中均有分布,侵入橄榄岩的部分岩脉已经变为变辉绿岩和异剥钙榴岩。辉绿岩床(墙)向上逐渐过渡为玄武岩。局部可见日喀则群整合覆盖在玄武岩之上。地球化学分析显示不同产状的镁铁质岩均属于低钾或中钾的拉斑玄武岩,亏损Nb、Ta、Ti和LREE,具有弧前玄武岩(FAB)或弧后盆地玄武岩(BABB)的特征,它们的Ti/V和Yb/V的比值与BABB或正常大洋中脊玄武岩(N-MORB)相似,Sr-Nd-Pb同位素数据指示了亏损地幔(DM)与富集地幔(EM)过渡的源区。镁铁质岩野外产出关系和地球化学特征表明,白马让蛇绿岩的镁铁质岩组合可能形成于SSZ环境。考虑到超镁铁质岩、镁铁质岩和日喀则群在空间上的连续性,认为白马让蛇绿岩可能是起源于亚洲大陆边缘俯冲带上的洋盆,属于原地系统,而非外来的构造岩片。 相似文献
18.
The Rainbow hydrothermal field (36° N Mid-Atlantic Ridge) is one of the three presently known fields related to serpentinization of ultramafic rocks accompanied by the formation of hydrogen- and methane-rich solutions. Gas chromatographic (GC) and molecular gas chromatographic–mass spectrometric (GC-MS) investigations of sulfide ores and sediments from this field confirmed a predominantly biological nature of bitumoids related to the high-temperature transformation of biomass of the hydrothermal biological community. At the same time, ores of the Rainbow field contain significant amounts of compounds that are not directly related to biogenic synthesis. This fact suggests the possibility of an abiogenic synthesis of methane and even complex hydrocarbons during the serpentinization of ultramafic rocks. 相似文献
19.
蛇纹岩体中的硬玉岩与异剥钙榴岩 总被引：1，自引：4，他引：1
硬玉岩是一种稀少的岩类，常以构造岩包体和脉体的型式产出在蛇纹岩中。本文着重介绍与蛇纹岩化过程密切相关的硬玉岩。这类硬玉岩总是出现在洋壳俯冲碰撞带中，常常与蓝片岩、偶尔也与榴辉岩伴生。通过研究硬玉岩的矿物组合、化学成分和结构构造，综合世界各地硬玉岩产状，可将硬玉岩从广义的变质成因上分为三类，即：在蛇纹岩体中、或其它岩类包体中由交代作用形成的硬玉岩脉体；蛇纹岩中的构造岩成因岩石包体经固相变质作用后形成的块状硬玉岩：以及介于上述两者之间，由变质和交代的共同作用形成的硬玉岩。此外，还对交代成因的硬玉岩在蛇纹岩化过程中与异剥钙榴岩化作用的关系从流体及其化学成分演化的角度进行了分析和研究。提出了在海底和俯冲带上板片的构造背景下硬玉岩形成的模式。 相似文献