滇西谦迈地区惠民组变质火山岩特征及构造环境

滇西澜沧县谦迈地区惠民岩组(Pt_2h)中含有较多的绿泥片岩,这些绿泥片岩的岩石学特征和岩石地球化学特征,表明其原岩至少可分为安山岩类和流纹岩类,前者具岛弧钙碱性火山岩特征,后者具火山弧花岗岩特征,总体上看惠民岩组中变质火山岩具有岛弧火山岩的性质。另外在钠长绿泥片岩中获得473.6±6.1Ma、459.5±9.2Ma和481.9±2.7Ma三个锆石LA-ICP-MS年龄值,这为该区惠民岩组的形成时代提供了新的依据。     

滇西惠民前寒武纪铁矿床的形成条件

滇西惠民前寒武纪变质铁矿床位于滇藏地槽区三江褶皱系中澜沧江变质带之南部,变质带内地层主要由澜沧群组成。该群分布于澜沧江西岸,北起昌宁,南至国境线,呈南北方向延展,长约三百余公里,宽约几十至百余公里。根据云南区调队在景洪、勐海等地所测剖面,澜沧群划为八个组,总厚度近万公尺,主要由斜长变粒岩、变质长石砂岩、白云片岩、二云片岩、绢云石英片岩(有的含碳)、石英片岩、千枚岩、以及少量大理岩所组成,在中——上部还夹有数层厚度不等的钠长绿泥片岩、钠长阳起片岩与硅质岩、绿泥千枚岩。而铁矿床在空间上与绿片岩密切有关。群内岩石呈互层状产出(单层厚由几十厘米～几米),韵律构造频繁而清楚。从组成该群变质岩的特点来看,其原岩应以砂质、半粘土质——粘土质的沉积岩为主,夹有中——基性火山岩,这套岩石组     

锡铁山铅锌矿地质特征、矿床成因及找矿标志

通过找矿工作的实践，认为锡铁山铅锌矿床是由火山喷流沉积—后期热液叠加改造富集的块状硫化物多金属矿床。区域上NW—SE向早古生代形成的裂谷带，三级盆地内沉积的晚奥陶世滩间山群的大理岩与绿片岩系是表区找矿的最佳区段。而绢云绿泥斜长片岩、含碳质绢云绿泥片岩、白色大理岩、条带状大理岩是铅锌矿的最重要的找矿标志。     

东秦岭商南赵川蓝片岩及其构造意义

东素岭商南地区的蓝片岩不是典型的蓝闪片岩相,它是由镁钠闪石、青铝闪石、多硅白云母和钠长岩等组成的高压低温绿片岩相。秦岭印支造山带是一个纯粹的陆间带,因为华北板块和杨子板块在早古生代末期已经碰撞。那里的蓝片岩是由于陆内俯冲而形成。     

东秦岭商南赵川蓝片岩及其构造意义

东素岭商南地区的蓝片岩不是典型的蓝闪片岩相,它是由镁钠闪石、青铝闪石、多硅白云母和钠长岩等组成的高压低温绿片岩相。秦岭印支造山带是一个纯粹的陆间带,因为华北板块和杨子板块在早古生代末期己经碰撞。那里的蓝片岩是由于陆内俯冲而形成。     

内蒙古中部早古生代白乃庙群韧性剪切变形特征

内蒙古中部地区早古生代白乃庙群地层主要由绿泥片岩段(Ob~1、Ob~3)和长英片岩段(Ob~2)组成,花岗闪长斑岩(386Ma)侵入于地层之中。白乃庙群和花岗闪长斑岩一同遭受了推覆型韧性剪切作用。     

甘肃某金银矿物化探异常的初步研究

一、地质特征 某金银矿所处大地构造位置为秦岭褶皱带北缘与北西向深大断裂带之间的过渡带上。沿该断裂带有不同期的许多中酸性岩体侵入。某金银矿就处于一背斜倾末端南侧的二长花岗岩体中。二长花岗岩呈岩舌伸入奥陶系地层中,矿化主要集中于岩舌部位,但在内、外接触带亦有矿化。(见图1a)地层岩性主要为绿泥绢云母石英片岩、黑云母石英片岩、阳起石绿泥片岩等。 矿化主要受岩体内破碎带控制,岩舌部位破碎带十分发育(见图1b),以NW为     

弓长岭铁矿床磁铁富矿形成机制探讨

弓长岭沉积变质型铁矿床是我国鞍山式铁矿床的典型代表,矿床中的磁铁富矿体的形成一直都是矿床研究的重点问题。研究表明,弓长岭富铁矿体赋存于反S型褶皱中,局部矿体出现褶曲现象。磁铁富矿体产于主要是由斜长角闪石、磁铁石英岩构成的含铁岩系中。磁铁富矿的围岩主要是绿泥片岩、石榴绿泥片岩、绿泥石榴岩和少量黑云母绿泥片岩。对绿泥石片岩、石榴绿泥片岩和绿泥石榴岩的常量、微量与稀土元素的研究和对绿泥石、石榴石、黑云母铁含量与磁铁矿品位的研究表明,含铁岩系在沉积间歇中出现的含铝的泥质-粉砂质物质在富铁矿形成过程中起对磁铁石英岩中带出的硅消耗（带入）形成石榴石、绿泥石、黑云母等的作用。区域变质作用为磁铁富矿的形成提供了储矿空间,同时区域变质作用产生变质热液,变质热液淋滤途经的磁铁石英岩可从中带出FeO,变质热液是磁铁富矿形成过程中重要的物质载体。在进变质过程中,区域变质作用为矿物转换提供所需的温压条件。可见,区域变质作用是磁铁富矿形成的重要条件。     

内蒙古白乃庙铜矿床的成矿时代—来自SHRIMP锆石U-Pb和辉钼矿Re-Os年龄的新证据

摘要：内蒙古白乃庙铜矿床位于兴蒙造山系满都拉-霍林郭勒弧盆系白乃庙早古生代岛弧内,该矿床包括南、北两个矿带,南矿带矿体产于白乃庙组绿片岩中,北矿带矿体产于花岗闪长斑岩内,对于该矿床及白乃庙组的形成时代争议较大。本文采用锆石SHRIMP U-Pb同位素定年获得了白乃庙组第三岩性段绿泥斜长片岩的形成年龄为439.8±6.7Ma,花岗闪长斑岩的形成年龄为433.9±2.2Ma、451.8±3.0Ma,采用辉钼矿Re-Os同位素分析获得辉钼矿的形成年龄为433.9±3.1Ma。结合前人成果,提出白乃庙组地层和花岗闪长斑岩的成岩时代与白乃庙铜矿的成矿时代均为晚奥陶-早志留世,它们同属加里东期构造-岩浆作用的产物。 关键词：绿泥斜长片岩;花岗闪长斑岩;锆石SHRIMP U-Pb年龄;辉钼矿Re-Os同位素年龄;白乃庙铜矿     

内蒙东升庙矿区狼山群中石英角斑岩的发现及意义

一系列证据表明,东升庙一带狼山群(Pt_2ls)中的石英钠长浅粒岩、百英钠长变粒岩和(绢云)石英钠长片岩的原岩是石英角斑岩。该类岩石多呈层稳定出现在块状白云石大理岩中,含有变余(钠长石和石英)斑晶;Na_2O=3.64％～5.31％、K_2O=1.62％～2.66％;具有与上下正常沉积地层相同的多期次构造特征。石英角斑岩的发现,既可直接佐证东升庙矿床形成于海底火山喷发的环境,也可为区域成岩成矿的研究对比提供有益信息。     

弓长岭鞍山群太古代基底岩石特征

弓长岭鞍山群呈北西至南东方向分布，位于中朝陆块东端，该群各类型岩石构成华北陆块古老的变质结晶基底。文中详细地记述了岩浆岩及混合岩、硅质板岩和长英质变粒岩、交超基性岩、交基性火山岩、变泥质岩、铁矿床、变辉长辉绿岩岩墙群的岩石特征和产出特征及成岩时代。本区为低压区域浅变质类型，演化与成岩时代约在太古代的中、晚期(3400～2500Ma)。     

台湾东澳片岩锆石U-Pb年龄及地质意义

台湾东澳片岩位于台湾东部,属太鲁阁带的北东部分,由绿泥绿帘片岩、绿泥钠长片岩、云母石英片岩、石英片岩夹含石墨云母片岩组成。在野外地质调查的基础上,结合岩石学、岩石主微量元素分析研究结果表明,原岩为玄武岩、副长岩或碱性玄武岩及陆源碎屑岩,岩石主要为碱性系列,具低Ba、Sr和高Pb,稀土总量普遍较低,具有轻稀土富集、铕无亏损的稀土分布模式,与陆源裂陷的火山(岩浆)-沉积作用特征类似;锆石可分为自形晶或尖棱角状、次棱角状及圆状三类;LA-ICP-MS锆石U-Pb年龄具多个峰值,其中206Pb/238U有4个,最小值为(95±3)Ma,为自形晶或尖棱角状锆石,代表了晚白垩世火山作用的时代;其余3个分别为(118±2)Ma(早白垩世)、(160±5)Ma(晚侏罗世)、(250±3)Ma(早三叠世),为次棱角状和少量自形晶锆石,代表了相应时代源岩的岩浆年龄;207Pb/206Pb表面年龄峰值2个,分别为(1838±41)Ma和(2404±27)Ma(古元古代),为磨圆状的变质锆石或岩浆锆石,代表了古元古代变质基底的年龄。东澳片岩形成时代为晚白垩世,属欧亚陆块边缘构造环境下火山-沉积作用的产物。     

黑龙江依兰地区黑硬绿泥石片岩岩石学与P-T条件研究

依兰地区黑龙江杂岩中黑硬绿泥石片岩矿物组合为黑硬绿泥+绿泥石+多硅白云母+钠长石+透闪石+钾长石±黑云母.岩石矿物学研究表明黑硬绿泥石片岩形成于250～400℃,6～9kbar的变质条件下.黄褐色黑硬绿泥石呈束状、放射状集合体.黑硬绿泥石片岩形成于佳木斯地块向西与松嫩地块俯冲拼贴过程中蓝片岩变质作用的后期,压力稍有降低而温度略有升高的变质变形环境,是蓝片岩向绿片岩转变的蓝闪绿片岩相变质条件下的产物.     

A study of natural and experimental metasomatic assemblages in an ultramafic-quartzofeldspathic metasomatic system from the haast schist,South Island,New Zealand

The mineralogy of a metasomatic sequence formed between ultramafic and quartzofeldspathic protoliths from the Southern Alps of New Zealand consists of a forsterite-antigorite core surrounded concentrically by zones of antigorite-magnesite, magnesite-talc, talc, tremolite, chlorite and muscovite with discontinuous pods of albite associated with the muscovite zone. On the basis of trace element data the original ultramafite-schist contact is positioned between the present tremolite and chlorite zones.An experimental study of a metasomatic system was undertaken in an attempt to clarify diffusion relationships during the metasomatic event. To simulate the natural event, ultramafic and quartzofeldspathic natural starting materials were tightly packed in a gold tube with a graphite layer between to allow later identification of the original lithological interface. Run conditions were 450° C at 2 kb for 40 days. Phase dissolution and formation were analysed petrographically and component migration was examined with the electron-microprobe. The following hierarchical scheme of component migration, phase dissolution and phase formation is delineated: CO₂ migrates from the schist into the ultramafite forming first the antigorite-magnesite zone and then the magnesite-talc zone at higher values of CO₂. These zones are then partially overprinted by the formation of talc due to SiO₂ metasomatism. The SiO₂ is supplied from the schist by the dissolution of quartz and albite in the region adjacent to the ultramafite. The tremolite zone forms at the expense of the metasomatic talc zone upon the introduction of CaO from the schist into the ultramafite. Concurrent with tremolite formation, MgO migrates from the ultramafite into the schist to form the chlorite metasomatic zone. The growth of the chlorite zone causes dissolution of the pre-metasomatic micas and displaces K₂O from the chlorite zone further into the schist. Displaced K₂O and Na₂O are responsible for the formation of the muscovite zone and the albitite pods.     

甘肃玉门昌马地区的蓝闪片岩

蓝闪片岩产于一套含放射虫硅质岩、硅质大理岩、板岩、变质基性火山岩中,与此相伴的超基性岩块,以一系列向南逆冲的断片产出。蓝闪片岩中的蓝闪石往往和黑硬绿泥石、钠长石、绿泥石以及钠钙闪石(蓝透闪石、冻蓝闪石等)、钙闪石(阳起石等)共存。据钠角闪石、绿泥石计算的生成压力是0.65GPa至0.8GPa,略大于美国佛兰西斯科的瓦尔德溪蓝片岩中该矿物对生成的压力。稀土元素分析证明蓝片岩的原岩是典型洋底(中脊)玄武岩和岛弧玄武岩,这是蓝片岩沟-弧俯冲-碰撞的证据之一。     

甘肃玉门昌马地区的蓝闪片岩

蓝闪片岩产于一套含放射虫硅质岩、硅质大理岩、板岩、变质基性火山岩中,与此相伴的超基性岩块,以一系列向南逆冲的断片产出。蓝闪片岩中的蓝闪石往往和黑硬绿泥石、钠长石、绿泥石以及钠钙闪石(蓝透闪石、冻蓝闪石等)、钙闪石(阳起石等)共存。据钠角闪石、绿泥石计算的生成压力是0.65GPa至0.8GPa,略大于美国佛兰西斯科的瓦尔德溪蓝片岩中该矿物对生成的压力。稀土元素分析证明蓝片岩的原岩是典型洋底(中脊)玄武岩和岛弧玄武岩,这是蓝片岩沟-弧俯冲-碰撞的证据之一。     

Geochemistry of blackwall sequences in the Habachtal emerald deposit,Hohe Tauern,Austria Part 1: Presentation of geochemical data

Summary The Habachtal emerald deposit, Hohe Tauern, is composed of blackwall sequences of the type: serpentinite — talc schist — ±chlorite schist or actinolite schist — biotite schist —albite gneiss and/or micaschist. 2 serpentinites, 33 blackwall rocks, 9 micaschists, 10 albite gneisses, and 5 aplitic gneisses were analyzed for major elements, and for Li, Be, Cr, Ni, Zn, Zr, Sn, in 36 samples also for Sc, Cu, Rb, Sr, Cs, Ba, W. The blackwall formation is due to a metasomatic exchange involving a transfer of Mg from the serpentinite to the silicic country rock, and of Si, Ca, K, and Al from the country rock to the serpentinite. Some of the trace elements were also mobile: Compared to serpentinite, Li and Be were enriched in all the blackwall rocks, and Sn and Cs in the actinolite, chlorite, and biotite schists; Sr was concentrated in the dolomite-bearing talc schists, and Zn, Rb, and Ba predominantly in the biotite schists.

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Geochemie der Blackwall-Folgen in der Smaragd-Lagerstätte Habachtal, Hohe Tauern, Österreich. Teil 1: Darstellung der geochemischen Daten

Zusammenfassung Die Smaragd-Lagerstätte Habachtal, Hohe Tauern, besteht aus Blackwall-Folgen vom Typ: Serpentinit — Talkschiefer — ±Chloritschiefer oder Aktinolithschiefer — Biotitschiefer — Albitgneis und/oder Glimmerschiefer. Von 2 Serpentiniten, 33 Blackwall-Gesteinen, 9 Glimmerschiefern, 10 Albitgneisen und 5 Aplitgneisen wurden chemische Analysen der Hauptelemente und von Li, Be, Cr, Ni, Zn, Zr, Sn vorgelegt; 36 Proben wurden auch auf Sc, Cu, Rb, Sr, Cs, Ba und W analysiert. Die Blackwall-Bildung geht auf einen metasomatischen Austausch zurück, bei dem Mg aus dem Serpentinit ins Nebengestein, Si, Ca, K und Al aus dem Nebengestein in den Serpentinit transportiert wurden. Daneben waren auch einige Spurenelemente mobil: Im Vergleich zum Serpentinit wurden Li und Be in allen Blackwall-Gesteinen, Sn und Cs in den Aktinolith-, Chlorit- und Biotitschiefern angereichert; Sr wurde(n) in den dolomitführenden Talkschiefern, Zn, Rb und Ba hauptsächlich in den Biotitschiefern konzentriert.

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With 5 Figures     

Whole-rock Geochemistry of Basic Schists from the Besshi Area, Central Shikoku: Implications for the Tectonic Setting of the Besshi Sulfide Deposit

Abstract. Whole-rock chemical compositions of the Besshi basic schist closely associated with the Besshi massive sulfide deposit from the Sanbagawa Belt are reported. Studied samples were collected from four outcrops around the Dozan-goe, central Shikoku. Common metamorphic mineral assemblage of the basic schist is albite + epidote + actinolite + chlorite ± muscovite ± quartz. Major element contents are similar to those of typical tholeiitic basalts. Trace element patterns of the basic schist normalized to normal mid-ocean ridge basalt (N-MORB) are generally flat, although concentrations of highly mobile large-ion lithophile elements are quite variable. Chondrite-normalized rare earth element (REE) patterns are flat to slightly light REE-depleted patterns. In the Hf-Th-Ta and Nb-Zr-Y discrimination diagrams, basic schist samples closely associated with the sulfide deposit are plotted within the N-MORB field. The Th/Nb ratios of the basic schist are also comparable to those of N-MORB. These geo-chemical lines of evidence indicate that the protolith of the Besshi basic schist is N-MORB and the Besshi sulfide deposit was formed by hydrothermal activity in conjunction with MOR volcanism.     

海水交代过程中细碧角斑岩的矿物组合和矿物成分的变化规律——以陕西略阳细碧角斑岩为例

对陕西略阳细碧角斑岩的矿物学、岩石学、岩石地球化学、以及全岩O同位素的研究，认为细碧角斑岩是海水与玄武安山岩的交代产物；交代作用初期岩石中的Na2O含量升高，而MgO、CaO降低；交代作用后期岩石中的MgO升高而Na2O含量降低，即在整个过程中岩石的Na2O含量是一个最大值，而MgO有一个最小值。矿物组合由钠长石、绿帘石、少量绿泥石组成，最终产物为绿泥石和石英。     

Occurrence of calcite in Sanbagawa pelitic schists: implications for the formation of garnet, rutile, oligoclase, biotite and hornblende

The frequency of occurrence of minerals in 1876 samples of Sanbagawa pelitic schist in central Shikoku is summarized on the basis of microscopic observation accompanied, in part, by use of an electron microprobe. All samples contain quartz, plagioclase, phengite, chlorite and graphite. More than 90% of samples contain clinozoisite, titanite and apatite. Garnet is present in 95% of samples from the garnet zone, and biotite is present in 64% of samples from the albite‐biotite zone. Calcite is found in about 40% of samples of the pelitic schist collected from outcrop, but occurs in 95% of the pelitic schist from drill cores. Calcite was apparently ubiquitous in the pelitic schist during the Sanbagawa metamorphism, but must have been dissolved recently by the action of surface or ground water. The mineral assemblages of the Sanbagawa pelitic schist have to be analyzed in the system with excess calcite, quartz, albite (or oligoclase), clinozoisite, graphite and fluid that is composed mainly of H₂O, CO₂ and CH₄. In the presence of calcite, reactions that produce garnet, rutile, oligoclase, biotite and hornblende, some of which define isograds of the metamorphic belt, should be written as mixed volatile equilibria that tend to take place at lower temperature than the dehydration reactions that have been proposed. The presence of calcite in pelitic schist suggests that fluid composition is a variable as important in determining mineral assemblages as pressure and temperature. Thus Ca‐bearing phases must be taken into account to analyze the phase relations of calcite‐bearing pelitic schist, even if CaO content of Sanbagawa pelitic schist is low. As calcite is a common phase, the mineral assemblages of the biotite zone pelitic schist may contravene the mineralogical phase rule and warrant further study.