共查询到18条相似文献，搜索用时 187 毫秒
1.
《吉林大学学报(地球科学版)》2015,(Z1)
<正>Knoblauch(1963)及Bausch(1980)的研究证明,所有泥岩、粉砂岩及砂岩中能出现的矿物可以在碳酸盐岩中出现。碳酸盐岩层系中除了包括常见的碳酸盐矿物(方解石(或低镁方解石)、镁方解石(高镁方解石)、文石、白云石、菱铁矿、菱镁矿、菱锰矿等),还包括少量(一般1%)的自生非碳酸盐矿物(硅质、黄铁矿、石膏和硬石膏等),以及陆源碎屑矿物(石英、长石、黏土矿物和重矿物等)。在以碳酸 相似文献
2.
X射线粉晶衍射仪在大理岩鉴定与分类中的应用 总被引：2，自引：2，他引：0
大理岩主要有方解石大理岩、白云石大理岩和菱镁矿大理岩三种。以往大理岩是依据偏光显微镜下观察岩石结构构造及矿物成分进行分类定名,由于方解石、白云石、菱镁矿都属于三方晶系,具有闪突起、高级白干涉色、一轴晶负光性和菱形解理等相同晶体光学特征,偏光显微镜下区分十分困难。为了准确鉴定大理岩中碳酸盐矿物种类及其相对含量,本文利用岩石薄片偏光显微镜和X射线粉晶衍射技术对32件大理岩岩石样品进行分析测试。岩石薄片鉴定结果表明:大理岩造岩矿物主要有方解石、白云石、菱镁矿、石英、斜长石、白云母、黑云母、绿泥石、黏土和金属矿物。根据岩石结构构造及矿物组分特征,可把32件大理岩样品划分为方解石大理岩、长英质方解石大理岩、石英绿泥白云石大理岩、白云石大理岩、云英质白云石大理岩和菱镁矿大理岩等15个类型。X射线粉晶衍射分析表明:大理岩造岩矿物主要有方解石、白云石、菱镁矿、石英、斜长石、钾长石、云母、绿泥石、滑石和蒙脱石。综合分析认为:岩石薄片偏光显微镜鉴定技术很难区分方解石、白云石和菱镁矿等碳酸盐矿物,以及细小的石英、钾长石和斜长石、滑石和白云母等鳞片状硅酸盐矿物;X射线粉晶衍射分析技术不仅能准确检测出大理岩中方解石、白云石和菱镁矿等碳酸盐矿物种类及相对含量(方解石、白云石和菱镁矿的X射线衍射主峰有明显差异,d值分别为0.303 nm、0.288 nm和0.274 nm),而且能够有效鉴别岩石中粉砂级斜长石、钾长石与石英(三种矿物的X射线衍射主峰d值分别为0.319 nm、0.324 nm、0.334 nm);且能区分蒙脱石、绿泥石、云母和滑石等层状硅酸盐矿物(四种硅酸盐矿物的X射线衍射主峰d值分别为1.400 nm、0.705 nm、0.989 nm、0.938 nm)。综合岩石薄片偏光显微镜鉴定和X射线粉晶衍射分析结果,最终确定32件大理岩样品划分为22个岩石类型。研究认为:仅根据岩石薄片偏光显微镜鉴定或X射线粉晶衍射技术其中一种方法不能准确鉴定大理岩岩石,应将大理岩岩石野外观察、岩石薄片鉴定和X射线粉晶衍射技术结合起来,才能准确确定大理岩岩石类型。 相似文献
3.
Gemerská Poloma矿床是个重要的滑石矿床(储量20万吨),位于西喀尔巴阡山脉Germeric地区。部分滑石化的镁质碳酸盐体赋存在早古生代火山沉积杂岩体中(黑色片岩,变质泥岩),在Variscan变质作用(M1)过程中受到了绿泥石-黑云母带区域变质相的改造。这种原岩是石灰岩的矿体由白色-灰白或者灰色-黑色的菱镁矿与白云石1组成,被次生的白云石2和滑石脉切割。本次研究考察了两次变质事件(M1和M2)的几个连续的矿物组合,最早的组合包括铁白云石,镁菱铁矿与菱铁矿,(并与黑电气石,铁绿泥石,磷灰石,与伊利石-白云母伴生),它们以微小残留物形式产出在菱镁矿和白云石1中,其形成可能早于M1变质作用高峰期。M1变质事件的高峰期以富铁金云母,镁绿泥石1,镁电气石(黑电气石的边缘)和石英的组合为代表。在M1退变质作用过程中,发生了镁交代作用,开始是白云石1结晶,接下来形成菱镁矿,最后是以铁菱镁矿沿裂隙的形成而终。根据碳酸盐地质测温原理,M1变质事件的高峰期温度为460~490℃,变质矿物组合特征也支持这一测温结果。滑石,白云石2,与镁绿泥石2沿着镁碳酸盐岩石裂隙的发育,主要受到M2变质事件的影响,这个变质事件与较年青的Alpine造山事件有关。 菱镁矿流体包裹体的研究表明,成矿流体具有复杂的组成,可能以MgCl2组分为主,主要来 相似文献
4.
Kosice矿床是斯洛伐克第二大的菱镁矿床(150Mt),位于Gemeric的东部。其镁质碳酸盐矿体赋存于石炭纪石灰石和含白云石的石灰石中,同时下盘黑色片岩中也含有被铁质碳酸盐交代的薄层碳酸盐透镜体。在华力西期造山运动(M1)中,古生代岩石受到了低级变质作用(绿泥石带)。镁交代作用始于白云岩1的结晶作用,其后形成菱镁矿,最终沿裂隙形成铁菱镁矿。铁质碳酸盐包括早期铁白云石-白云石,铁白云石和后期含方解石和石英的菱铁矿。根据碳酸盐矿物对地质温度计,白云石1结晶作用发生在300~340℃。这一结果与M1的变质矿物组合(绿泥石,白云母-伊利石)吻合。铁白云石的结晶作用发生在320~370℃.少量细脉中可见白云石2,绿泥石和伊利石-多硅白云母,它们是由于阿尔卑斯期造山运动M2变质作用形成的更晚的矿物组合。 菱镁矿的流体包裹体(FI)研究,显示存在不同成分的热卤水,卤水成分变化相当于NaCl含量21~42wt％,但其它成分的盐含量高于NaCl,溶解的CO2含量也有变化。两相包裹体均一温度(Th)的范围为164~217℃,含石盐子晶包裹体均一温度的范围为217~344℃。富CO2包裹体(盐度相当于NaCl含量1-22wt％,CO2的密度为0.28~0.77 g·cm-3,均一温度为289~344℃)在菱镁矿中是次要的,但这种包裹体在与矿石伴生的石英中是主要的,并且与含石盐 相似文献
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6.
Martin RADVANEC Peter KOD 《岩石学报》2004,20(4):855-876
Kosice矿床是斯洛伐克第二大的菱镁矿床(150Mt),位于Gemeric的东部.其镁质碳酸盐矿体赋存于石炭纪石灰石和含白云石的石灰石中,同时下盘黑色片岩中也含有被铁质碳酸盐交代的薄层碳酸盐透镜体.在华力西期造山运动(M1)中,古生代岩石受到了低级变质作用(绿泥石带).镁交代作用始于白云岩1的结晶作用,其后形成菱镁矿,最终沿裂隙形成铁菱镁矿.铁质碳酸盐包括早期铁白云石-白云石,铁白云石和后期含方解石和石英的菱铁矿.根据碳酸盐矿物对地质温度计,白云石l结晶作用发生在300～340℃.这一结果与M1的变质矿物组合(绿泥石,白云母-伊利石)吻合.铁白云石的结晶作用发生在320～370℃.少量细脉中可见白云石2,绿泥石和伊利石-多硅白云母,它们是由于阿尔卑斯期造山运动M2变质作用形成的更晚的矿物组合.菱镁矿的流体包裹体(FI)研究,显示存在不同成分的热卤水,卤水成分变化相当于NaCl含量21～42
wt%,但其它成分的盐含量高于NaCl,溶解的CO2含量也有变化.两相包裹体均一温度(Th)的范围为164～217℃,含石盐子晶包裹体均一温度的范围为217～344℃.富CO2包裹体(盐度相当于NaCl含量1～22wt%,CO2的密度为0.28～0.77
g·cm-3,均一温度为289～344℃)在菱镁矿中是次要的,但这种包裹体在与矿石伴生的石英中是主要的,并且与含石盐子晶流体包裹体共生.在后期镁交代过程中流体中的CO2逐渐增加.和铁质碳酸盐伴生的石英中只有两相包裹体,包裹体中CO2含量有所变化,盐度范围为17～24
wt%的NaCl(或者34～36 wt%的MgCl2),均一温度为152～195℃.包裹体的数据结合碳酸盐地质温度计显示镁交代作用的压力范围是180～320MPa(7～12km),铁交代作用的压力范围是280～420MPa(10～16km),说明地热梯度约为25～35℃/km.包裹体浸出液的分析表明Cl/Br和Na/Br的比值存在变化,但仍旧说明富镁的卤水来源是上二叠纪和下三叠纪的分馏蒸发岩来源.铁质碳酸盐流体的高溴和高碘含量,说明在铁交代过程中周围黑色片岩的明显影响.菱镁矿和铁交代作用,表明交代流体中的碳和二氧化碳,主要是海洋沉积的来源.菱铁矿的"Sr/86Sr比值((0.71124～0.71140),说明锶的多来源,最初应是石炭纪和二叠纪的海水,但它被当地其它陆壳中的锶混染. 相似文献
7.
用Y／Ho比值指示俄罗斯乌拉尔南部晶质菱镁矿矿床的成因 总被引：1，自引：1，他引：1
Mikhail T KRUPENIN 《岩石学报》2004,20(4):803-816
乌拉尔省南部赋存有两种类型的晶质菱镁矿:1)白云岩地层中的层状矿体;2)白云质灰岩中的透镜状矿体。晶质菱镁矿矿体位于Riphean系列中下层的白云岩中,而在上层的白云岩单元中缺失。这两种类型的菱镁矿可通过矿体形态、晶体大小、石英和白云石含量不同来进行区分。第一种类型的菱镁矿储量巨大,菱镁矿呈粗粒结构,晶体粒径>10mm(最大达150mm);一般来说,矿体与白云岩围岩界限清楚,这种类型矿床以产在Riphean序列下部为特征。第二种类型的菱镁矿由于菱镁矿矿体穿插进入到白云岩围岩中,矿体很不规则,菱镁矿晶体也相对较小(1-5mm),这种类型的矿体主要产在Riphean中部层位中。这两种矿体都显示了交代成因的特征。但这两种菱镁矿矿石在一些主量元素和稀土元素的分布上具有不同的特征:与第二种类型相比,第一种菱镁矿具有较低的FeO,CaO和SiO2含量,与白云岩围岩(La／Lu>1)相比,具La／Lu<1的轻稀土亏损特征。第二种菱镁矿稀土分馏度较低,在稀土分配方面与白云岩围岩有差别。本文还特别讨论了Y／Ho值的重要性,因为该比值在菱镁矿和围岩中的类似性使得划分菱镁矿形成中的热液和成岩交代过程成为可能。因此我们认为,第一种类型菱镁矿,如具有高Y／Ho比值的Satka和Bakal矿床的形成属于沉积盆地发育过程中的早期成岩阶段;第 相似文献
8.
Martin RADVANEC Peter KOD《岩石学报》 2004,20(4):773-790
Gemerska
Poloma矿床是个重要的滑石矿床(储量20万吨),位于西喀尔巴阡山脉Germeric地区.部分滑石化的镁质碳酸盐体赋存在早古生代火山沉积杂岩体中(黑色片岩,变质泥岩),在Variscan变质作用(M1)过程中受到了绿泥石-黑云母带区域变质相的改造.这种原岩是石灰岩的矿体由白色-灰白或者灰色-黑色的菱镁矿与白云石1组成,被次生的白云石2和滑石脉切割.本次研究考察了两次变质事件(M1和M2)的几个连续的矿物组合,最早的组合包括铁白云石,镁菱铁矿与菱铁矿,(并与黑电气石,铁绿泥石,磷灰石,与伊利石-白云母伴生),它们以微小残留物形式产出在菱镁矿和白云石1中,其形成可能早于M1变质作用高峰期.M1变质事件的高峰期以富铁金云母,镁绿泥石1,镁电气石(黑电气石的边缘)和石英的组合为代表.在M1退变质作用过程中,发生了镁交代作用,开始是白云石1结晶,接下来形成菱镁矿,最后是以铁菱镁矿沿裂隙的形成而终.根据碳酸盐地质测温原理,M1变质事件的高峰期温度为460～490°C,变质矿物组合特征也支持这一测温结果.滑石,白云石2,与镁绿泥石2沿着镁碳酸盐岩石裂隙的发育,主要受到M2变质事件的影响,这个变质事件与较年青的Alpine造山事件有关.菱镁矿流体包裹体的研究表明,成矿流体具有复杂的组成,可能以MgCl2组分为主,主要来源于蒸发卤水的演化.原生流体包裹体的盐度～35(wt%MgCl2),均一温度变化范围是216～235℃.石英中流体包裹体也显示了以MgCl2组分为主的相似流体组成,但均一温度比较高,为248～313℃.如果假定石英与M1变质事件同期,那么由流体包裹体计算出的M1变质峰期压力范围是250～350MPa(9～13km),因此地温梯度是35～40℃/km.假定这个梯度在镁交代成矿过程中保持不变,那么相关流体在180～280MPa(7～11km)的压力下的温度为300～350℃.流体包裹体的淋滤分析表明,流体中Cl/Br与Na/Br都很高,说明流体具有蒸发特征.而在Gemeric地区只有在晚二叠纪到早三叠纪这段时间才有如此大量的卤水形成.因此,二叠纪的伸展构造运动与形成菱镁矿的热液系统的形成有关. 相似文献
9.
在阿尔卑斯型超镁铁岩体边缘,分布有含碳酸盐超镁铁岩,即V·Lobochnikov等称的滑石菱镁片岩(Iistwaerite),其中可以见到汞、砷、钻—镍砷化物等各种矿化。此外,还已知产有一些金矿,但金与滑石菱镁片岩及超镁铁质围岩的成因关系仍存在疑问。为此,我们对上元古界(摩洛哥、沙特阿拉伯)和阿尔卑斯(利古里亚)蛇绿岩杂岩的含金滑石菱镁片岩进行了研究。 滑石菱镁片岩中金的分布是随机的,在上述三研究区,大多数样品的金含量相似,即0.02—1ppm,为伴生的超镁铁岩含金量(5—100ppb)之10—100倍。看来,滑石菱镁片岩是含金很富的一种岩类。滑石菱镁片岩的最高含金量为1—10ppm(达边界品位),与富黄铁矿带有关,尤其与砷化钴矿化有关(如摩洛哥的布阿泽尔地区),也与含副矿物黄铁矿或毒砂的晚期石英脉(含金0.2—10ppm)有关。实际上,从单矿物分析表明,滑石菱镁片岩中的主要含金矿物是黄铁矿(含金10—50ppm)和砷化钴(含金10—100ppm)。在上述矿物中 相似文献
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超高压变质大理岩中的白云石分解结构：大陆地壳物质深循环的新证据 总被引：11，自引：7，他引：4
苏鲁超高压变质地体中产出的与柯石英榴辉岩共生的大理岩发生了不同程度的退变,根据退变程度差异识别出三类大理岩菱镁矿大理岩(弱退变)、滑石大理岩(中等退变)和透闪石大理岩(强烈退变).菱镁矿大理岩的稳定矿物组合是单斜辉石+白云石+方解石,菱镁矿仅仅在方解石中与方解石集合体镶嵌共存.单斜辉石发育出溶结构且局部形成由角闪石和钠长石组成的后成合晶.另外两类大理岩不含菱镁矿,但含滑石和/或透闪石.在菱镁矿大理岩中观察到白云石的分解反应(Mg,Ca)(CO3)2=MgCO3+CaCO3,说明这些大理岩是大陆地壳物质俯冲到地幔＞180 km(甚至超过210 km)后返回到地表的产物.所观察到的白云石分解反应表明,苏鲁地区大陆地壳物质在所谓的"地幔禁区"俯冲,俯冲的温度增加梯度可能为～4.2℃/km.大陆地壳物质以如此低的温度梯度俯冲意味着非常高的俯冲速度.如此深循环的大陆地壳物质同时也经历了非常快的折返过程.这是白云石分解结构这种标志超高压条件下进变质反应阶段的证据得到保存的重要原因. 相似文献
11.
Rajesh Sharma Prabha Joshi P. D. Pant 《Journal of the Geological Society of India》2009,73(2):237-248
Talc deposits of Rema area in the Kumaun Inner Lesser Himalaya are hosted within high magnesium carbonates of the Proterozoic
Deoban Formation. These deposits occur as irregular patches or pockets mainly within magnesite bodies, along with impurities
of magnesite, dolomite and clinochlore. Textures represent different phases of reactions between magnesite and silica to produce
talc. Petrography, XRD and geochemistry reveal that the talc has primarily developed at the expense of magnesite and silica,
leaving dolomite largely un-reacted. Early fluid inclusions in magnesite and dolomite associated with talc are filled with
H2O+NaCl+KCl ± MgCl2 ± CaCl2 fluids, which represent basin fluid system during diagenesis of carbonates. Their varied degree of re-equilibration was although
not pervasive but points to increased burial, and hence requires careful interpretation. H2O-CO2 fluid with XCO2 between 0.06 and 0.12 was equilibrated with talc formation. The reaction dolomite+quartz → talc was not extensive because
T-XCO2 was not favourable, and talc was developed principally after magnesite+quartz. 相似文献
12.
R. Ellmies G. Voigtländer K. Germann M. T. Krupenin P. Möller 《International Journal of Earth Sciences》1999,87(4):589-602
In the Bashkir mega-anticline (western Urals) stratabound magnesite, siderite, fluorite and base-metal deposits are hosted by a sequence of Riphean sediments with a thickness of more than 12 km. The giant deposits of siderite (Bakal) and sparry magnesite (Satka) belong to the largest known mineral deposits of this type on Earth but are still disputed with respect to their origin. Both the Fe- and Mg-carbonate ores are clearly characterized by mimetic preservation of sedimentary and diagenetic textures of the host carbonate sediments, giving evidence of epigenetic metasomatic replacement. In the stratiform magnesite deposits of Satka, O- and C-isotopes, REE pattern and the lithostratigraphic position of the ore, point to the reflux of early diagenetic Mg-rich brines being responsible for the selective replacement of brecciated dolomite. The Bakal siderite deposits are hosted by Lower Riphean carbonate rocks and are controlled by a Lower to Middle Riphean unconformity marked by deep erosion and subsequent transgression-related sedimentation of coarse clastics. Their independence of carbonate lithofacies and their trace element distribution are indicative of metasomatic processes. Fe-bearing fluids have probably been generated by low-grade metamorphic (catagenetic) devolatization from underlying argillites, causing the metasomatic formation of large siderite ore bodies in the Bakal carbonates due to the focusing of the fluid flow by the overlying Mid-Riphean coarse clastics. 相似文献
13.
G. V. Ovchinnikova A. B. Kuznetsov M. T. Krupenin I. M. Vasil’eva O. K. Kaurova 《Doklady Earth Sciences》2018,481(2):1040-1044
For the first time, the age of magnesite in the Lower Riphean Bakal Formation of the Southern Urals is determined by the U—Pb (Pb—Pb) method: it is equal to 1366 ± 47 Ma (MSWD = 18). The stage of magnesite formation of the Bakal ore field was associated with the Mashak rifting pulse and took place prior to the formation of industrial deposits of the Bakal siderite. 相似文献
14.
《Resource Geology》2018,68(4):352-372
Talc deposits in Nangarhar Province, are hosted by Paleoproterozoic carbonate rocks, metamorphosed to amphibolite facies in the east–west (E–W) trending Spinghar Fault Block. Many deposits in this province have potential economic importance. However, detailed geologic and petrological studies on ore genesis are still lacking. In this study, eight talc deposits and two prospects of the Spinghar Fault Block were investigated. Talc is mainly formed by alteration of the host dolomite marble, magnesite rocks, and tremolitite. Talc ore bodies occur parallel to subparallel to the beddings of the host carbonate rocks. Dolerite occur as dikes and sills and are mostly metamorphosed to amphibolite. Although the amphibolite occurs mostly parallel to subparallel to the beddings of the host carbonate rocks, and talc orebodies, it partly crosscuts the host rocks. Massive layers of tremolitite were observed with most of the talc ore bodies. Quartz veins occur along the gneissosity of gneiss all over the study area. SiO2 and MgO content in talc rocks from all deposits ranged from 49.1 to 65.1 wt% and from 26.1 to 32.9 wt%, respectively. CaO content in talc rocks and magnesite rocks are less than 1 wt%. ƩREE content in talc rocks ranged from 0.1 to 8.9 ppm. Chemical compositions of host carbonate rocks are close to the ideal composition. Concentrations of Al, Ta, Hf, Zr, Th, Cr, Ni, Co, and ƩREE in talc ores and host carbonate rocks were very low and inconsistent with mafic and ultramafic rocks protolith. Therefore, the metamorphosed sedimentary carbonate rocks were likely to be the protolith of the talc ores. The occurrence of parallel to subparallel quartz veins to the gneissosity of gneiss, as well as the presence of hydrous minerals in host carbonate rocks, suggested that hydrothermal fluids were most probably supplied through the gneiss. 相似文献
15.
Hans C. Oskierski Judy G. Bailey Eric M. Kennedy Geraldine Jacobsen Paul M. Ashley Bogdan Z. Dlugogorski 《Mineralium Deposita》2013,48(4):525-541
Nodular, cryptocrystalline, weathering-derived magnesite deposits in the New England Orogen, Australia, provide a significant source of high-purity magnesite. Common textural features and related isotopic fingerprints indicate a close genetic relationship between weathering-derived magnesite deposits hosted by ultramafic rocks at Attunga and by sediments at Kunwarara while silica-carbonate rock alteration and rare hydrothermal magnesite vein deposits reflect contrasting conditions of formation. Localised weathering of carbonates in a soil environment shifts stable isotopic composition towards low δ 13C and high δ 18O typical for weathering-derived magnesites while intrusion-related fluids do not significantly change the isotopic composition of affected carbonates. At Attunga, magnesite consists of irregular, nodular veins and masses filling faults and cracks in the weathered serpentinite host rock as well as soft powdery magnesite in pervasive serpentinite alteration zones. The high-grade magnesite at Attunga can be contaminated by amorphous silica and serpentine relicts but does not contain dolomite or ferroan magnesite as observed for its hydrothermal equivalent, the Piedmont magnesite deposit, or other widespread deposits of silica-carbonate rock in the Great Serpentinite Belt. Heavy δ 18O values are compatible with a supergene formation from meteoric waters while low δ 13C suggests C3-photosynthetic plants as the predominant source of carbon for the Attunga magnesites. We infer that weathering-derived, nodular magnesite deposits hosted in ultramafic rocks like the Attunga magnesite deposit have formed in a two-step process involving the hypogene formation of a pre-cursor magnesite deposit and complete supergene overprinting by meteoric waters that acquired carbon from percolation through soil. 相似文献
16.
The Jianchaling nickel deposit in the Bikou Terrane (Shaanxi Province, China) occurs along the boundaries between granite porphyry and carbonated ultramafic rocks (carbonated serpentinite, talc–carbonate rocks, and listwaenite). Serpentine– magnetite, serpentine– magnesite– magnetite, and magnesite– talc– quartz– pyrite– violarite– millerite– chalcopyrite assemblage formed in carbonated ultramafic rocks during hydrothermal activities. Ni-bearing sulphides, coexisting with magnesite, postdated magnetite in carbonated ultramafic rocks. Compared with serpentinite, Ni, Co, Cu, Mn, and Pb concentrate in talc–carbonate rocks. The fact that the NiO contents of magnetite decrease with progressive carbonation of serpentinite suggests that Ni from magnetite concentrated in fluid and contributed to the formation of the Jianchaling nickel deposit. Sulphides precipitated from fluid with log fO2 value varying from −34.5 to −31.8 and log fS2 value varying from −10.3 to −9.2. High pH and HS− activities triggered by transformation of serpentine into magnesite–talc–quartz assemblage promoted precipitation of Ni-bearing sulphides, and finally formed the Jianchaling hydrothermal nickel deposit. 相似文献
17.
试论与布什维尔德杂岩体有关的铂族元素-铬铁矿矿床成矿系列及其对中国西南部的意义 总被引：12，自引：0，他引：12
布什维尔德杂岩体中铂族元素成矿作用具有多样性的特点,既有主岩体岩浆结晶分异形成的UG2和Merensky层,有晚期小岩体结晶分异产生的块状铜镍硫化物矿石中伴生的铂族元素矿床（如Nkomati）,也有岩体侵入过程中产于接触带的热液成因硫化物-铂族元素矿床（如Potgietersrust）,以及岩筒型矿床（如Mooihoek和Driekop）、剪切带热液型硫化物矿床（如TweefonteinHill）和石英脉型铂族元素矿床.这些矿床虽然产出部位不同（矿体可以分布在岩体内部也可以出现在接触带甚至远离岩体）,矿石类型也不同（有的是铬铁矿型,有的是硫化物型,有的是硅酸盐型,甚至还有石英脉型）,但铂族元素的富集都与布什维尔德基性超基性岩杂岩体密切有关,实际上构成一个完整的由布什维尔德地幔柱形成的矿床成矿系列。类似的矿床成矿系列在深受峨眉地幔柱影响的我国西南部地区也存在,这对于在我国寻找多种类型的铂族元素矿床无疑具有重要的启示意义.除了金宝山和杨柳坪等地的岩浆型铂矿外,近年来在杨柳坪、大岩子等地也先后发现了热液型铂族元素矿床. 相似文献
18.
On the basis of a representative collection of ultramafic rocks and chromite ores and a series of technological samples from the largest (Central and Western) deposits in the Rai-Iz massif of the Polar Urals and the Almaz-Zhemchuzhina and Poiskovy deposits in the Kempirsai massif of the southern Urals, the distribution and speciation of platinum-group elements (PGE) in various type sections of mafic-ultramafic massifs of the Main ophiolite belt of the Urals have been studied. Spectral-chemical and spectrophotometric analyses were carried out to estimate PGE in 700 samples of ultramafic rocks and chromite ores; 400 analyses of minerals from rocks, ores, and concentrates and 100 analyses of PGE minerals (PGM) in chromite ores and concentrates were performed using an electron microprobe. Near-chondritic and nonchondritic PGE patterns in chromitebearing sections have been identified. PGE mineralization has been established to occur in chromite ore from all parts of the mafic-ultramafic massifs in the Main ophiolite belt of the Urals. The PGE deposits and occurrences discovered therein are attributed to four types (Kraka, Kempirsai, Nurali-Upper Neiva, and Shandasha), which are different in mode of geological occurrence, geochemical specialization, and placer-forming capability. Fluid-bearing minerals of the pargasite-edenite series have been identified for the first time in the matrix of chromite ore of the Kempirsai massif (the Almaz-Zhemchuzhina deposit) and Voikar-Syn’ya massif (the Kershor deposit). The PGE grade in various types of chromite ore ranges from 0.1–0.2 to 1–2 g/t or higher. According to technological sampling, the average PGE grade in the largest deposits of the southeastern ore field of the Kempirsai massif is 0.5–0.7 g/t. Due to the occurrence of most PGE as PGM 10–100 mm in size and the proved feasibility of their recovery into nickel alloys, chromites of the Kempirsai massif can be considered a complex ore with elevated and locally high Os, Ir, and Ru contents. The Nurali-Upper Neiva type of ore is characterized by small-sized primary deposits, which nevertheless are the main source of large Os-Ir placers in the Miass and Nev’yansk districts of the southern and central Urals, respectively. 相似文献