共查询到20条相似文献，搜索用时 140 毫秒
1.
圭亚那地盾位于南美洲亚马孙克拉通的北部,其北部广泛发育太古宙典型的花岗岩-绿岩带,主要岩石组成为花岗岩、片麻岩和英云闪长岩,古元古代变质超基性-基性火山岩-侵入岩、其他变质火山岩等。由于独特的地质构造位置和复杂的构造演化历史,形成了良好的绿岩型金成矿地质背景,产生了大量的金矿床。通过总结圭亚那地盾北部绿岩带的岩石特征、成岩时代和构造演化历史,对委内瑞拉埃尔卡劳金矿、圭亚那欧迈金矿和苏里南罗瑟贝尔金矿进行典型矿床剖析,系统研究了该区绿岩带型金矿的成矿地质背景、成矿流体及成矿年代学特征,建立了区域绿岩带型金矿成矿模型,并在分析找矿要素的基础上,提出圭亚那地盾北部的金矿找矿方向。 相似文献
2.
新太古代清原绿岩带位于华北克拉通北缘,该绿岩带中发育独特的VMS和BIF(Algoma型)组合,其中下甸子铁矿是此类BIF的典型代表。下甸子BIF赋存于绿岩带南天门组下部,围岩及夹层为斜长角闪岩及少量石榴云母片岩。矿体夹层斜长角闪岩中锆石的SIMS年代学分析获得了2497.8±7.4Ma的变质年龄,而原位氧同位素分析显示变质锆石的δ18O值为5.3‰~6.2‰,与现代地幔基本一致,表明在变质过程中其锆石的氧同位素体系保持稳定。BIF矿石类型主要有硅酸盐型和含黄铁矿条带型两种,前者的矿物组合为石英、磁铁矿和铁阳起石,而后者的矿物组合为石英、磁铁矿、阳起石、黄铁矿和少量方解石。大部分矿石的Al_2O_3、TiO_2和HFSE(如,Zr、Hf、Th、U等)含量极低,说明其未受到碎屑物质混染,PAAS标准化后,两类矿石稀土元素显示与海水类似的特征,即La、Y的正异常和LREE相对于HREE的亏损;同时,显著的正Eu异常指示成矿过程中有海底高温热液组分的参与;此外,所有样品均无明显的Ce异常,表明其沉淀自还原的海水中。通过与华北地区其他Algoma型BIF对比发现,下甸子两类矿石均具有较高的CaO/(CaO+MgO)值以及接近球粒陨石的Y/Ho值,表明其可能沉淀环境与海底热液喷口较近,且热液组分(以高温热液为主,可能有少量低温热液)的贡献较大。相比于硅酸盐型矿石,含黄铁矿条带型矿石的HREE含量较低、Eu正异常和LREE含量偏高,这可能与其沉淀过程中海底的局部热液的脉动式活动有关,其中黄铁矿条带可能为热液喷流沉积成因。BIF围岩斜长角闪岩的地球化学特征分析显示,其原岩玄武质岩石的岩浆可能来自亏损地幔,但在上升过程中受到了少量陆壳物质的混染,结合前人对清原绿岩带表壳岩系和TTG的年代学及地球化学研究,推测下甸子BIF可能形成于晚太古代洋陆俯冲过程中的火山弧或弧后盆地环境中。 相似文献
3.
华北陆台太古宙绿岩带金矿的成矿特征 总被引：15，自引：0，他引：15
华北陆台大多数的金矿床均产在绿岩带及与之有成因联系的岩浆岩中。绿岩带金矿可划分为原生金矿床和再生金矿床两类。原生金矿床可细分为层控金矿床和脉状金矿床，再生金矿床主要为与交代重熔岩浆作用有关的热液金矿。地层岩性、构造和岩体是绿岩带金矿的主要控矿因素。绿岩带金矿成矿物质主要来自深部，成矿流体为富含ＣＯ＿２的多成因混合热水溶液。成矿作用常是多期、多阶段。华北陆台绿岩带金矿同世界绿岩带金矿相比，既有相似性，又有独特性。 相似文献
4.
珠江口盆地惠州凹陷古近系物源分析 总被引：3，自引：0，他引：3
利用砂岩碎屑颗粒类型、砂岩组分阴极发光、重矿物组合、砂体百分含量变化,以及岩相古地理格局等物源分析的方法,对珠江口盆地惠州凹陷古近纪沉积期进行了物源分析。结果表明,恩平组发育了一套沼泽、三角洲-浅湖沉积体系,物源来自于盆地北部和中部隆起带;珠海组发育了一套三角洲-浅海沉积体系,物源来源于北部隆起带。 相似文献
5.
侏罗纪是大别造山带与周缘盆地盆山关系研究的一个重要时期,分布在大别造山带周缘的侏罗纪地层为大别山的造山过程以及深俯冲岩石的折返、剥蚀提供了很好的约束。本文选取大别造山带东南缘安庆月山地区侏罗系磨山组为研究对象,对磨山组碎屑岩进行了详细的粒度分析、碎屑组分分析、重矿物分析和碎屑锆石年代学分析。碎屑岩岩石、沉积特征和粒度分析都指示早侏罗世磨山组为三角洲前缘水下分流河道沉积。碎屑组分分析、重矿物分析结合碎屑锆石年代学分析指示磨山组碎屑岩物源主要来自南侧的华南板块,大别造山带宿松杂岩可能为其提供了少量物源,但碎屑物源中未见石榴子石和典型的三叠纪变质锆石,说明此时大别高压-超高压榴辉岩可能仍未折返至地表。 相似文献
6.
分析旧司阶—吴家坪阶额济纳旗及其邻区主要地层中的碎屑岩重矿物组合特征,结合区域地质特征、碎屑岩岩石学特征、碎屑锆石测年资料、古水流方向、沉积体系特征等,阐述了石炭系—二叠系沉积物的物源体系。重矿物组合特征显示,研究区北部黑鹰山-额济纳旗坳陷和南部的柳园-芒汗超克坳陷的碎屑岩重矿物组合类型和含量都有差异,指示它们来自不同的物源区;碎屑锆石测年资料显示,绿园-拐子湖凹陷的埋汗哈达剖面埋汗哈达组碎屑锆石的年龄可分为2类：436Ma±13Ma和1467Ma±110Ma,古水流方向也显示有北部物源区存在,说明沉积物源受敦煌-阿拉善-狼山古陆和马鬃山-拐子湖隆起带的双重作用;北部坳陷沉积物源来自马鬃山-拐子湖隆起带。 相似文献
7.
分析旧司阶—吴家坪阶额济纳旗及其邻区主要地层中的碎屑岩重矿物组合特征,结合区域地质特征、碎屑岩岩石学特征、碎屑锆石测年资料、古水流方向、沉积体系特征等,阐述了石炭系—二叠系沉积物的物源体系。重矿物组合特征显示,研究区北部黑鹰山-额济纳旗坳陷和南部的柳园-芒汗超克坳陷的碎屑岩重矿物组合类型和含量都有差异,指示它们来自不同的物源区;碎屑锆石测年资料显示,绿园-拐子湖凹陷的埋汗哈达剖面埋汗哈达组碎屑锆石的年龄可分为2类：436Ma±13Ma和1467Ma±110Ma,古水流方向也显示有北部物源区存在,说明沉积物源受敦煌－阿拉善－狼山古陆和马鬃山-拐子湖隆起带的双重作用;北部坳陷沉积物源来自马鬃山-拐子湖隆起带。 相似文献
8.
9.
津巴布韦太古宙花岗-绿岩型金矿床受构造的控制,金矿可分为褶皱控矿型、剪切带控矿型、层控型、深成花岗岩控矿型和构造-蚀变岩型等5类。津巴布韦花岗-绿岩型金矿多产于花岗质片麻岩与绿岩带的接触带上,金以自然金或金的硫化物形式产出。金矿成矿时代大致分为(2660±50)Ma和(2410±70)Ma(米德兰德绿岩带北部白钨矿Sm-Nd测年)2个时段,分别与新太古代TTG事件和大岩墙侵入相关。津巴布韦花岗-绿岩型金矿较多,但发现的中-大型绿岩型金矿较少,具有较好的金矿找矿前景。 相似文献
10.
通过对华北陆台北缘1:100万重磁异常图的地质研究和综合分析,认为华北陆台北缘由东胜、赤峰和辽东二个太古宙地块组成。在三个地块的边界地带和内部深大断裂带附近有晚太古宙绿岩带分布,表明三个地块在晚太古—早元古早期(约2500Ma)可能衔接在一起。三个地块北部都存在一边缘隆起带,但重磁异常场不连续,反映它们各自的基底演化历史的不同。根据三个地块上的重磁异常场推断的断裂带方位比较,表明各地块之间的相对运动主要沿这些深大断裂带进行。 相似文献
11.
本文通过对胶东地区早前寒武变质地层和花岗岩的研究，提出胶东绿岩带在变质地层、同位素年龄、变质程度、韧性剪切带和矿产等方面存在的证据，与世界典型绿岩带相比，胶东绿岩带具有５个方面的显著特征：①胶东绿岩带下部层位未发现完整科马提岩地层；②胶东绿岩带变质程度较高，一般可达角闪岩相，少数达麻粒岩相；③胶东绿岩带分布面积不大；④胶东绿岩带形成时间在２８．５８～２６亿ａ；⑤胶东绿岩带主要产出Ａｕ，Ａｇ，Ｚｎ，Ｃｕ等矿产。 相似文献
12.
《International Geology Review》2012,54(12):1166-1181
Geological and isotope-geochemical studies of acid volcanics in the Verkhovtsevo greenstone belt and surrounding tonalite-trondhjemite plutons within the central Dnieper gneiss-green- stone terrain were conducted in the search for genetic relationships and increased understanding of the petrogenesis of acid melts. The acid volcanic and plutonic rocks are similar in mineral composition and form a unified calc-alkaline-like trend from dacite/tonalite to rhyolite/ trondhjemite. Dacites and tonalites have the same rare-earth element (REE) patterns with moderately fractionated light and heavy REE as well as small negative Eu anomalies. Rhyolite and trondhjemites have less-fractionated REE patterns with larger negative Eu anomalies. Whole-rock data for the acid volcanic and plutonic rocks yielded a single isochron of 3117 ± 204 Ma, εNd = +1.14 ± 0.80. The data suggest a temporal and genetic relationship between the acid volcanics of the greenstone sequences and the surrounding plutonic rocks; both appear to belong to a single suite. The positive eNd value tends to suggest that a source of their melts can be traced to mafic materials rather than to older sialic crust. Petrochemical data and REE-model calculations suggest that dacite/tonalite liquids might have formed during partial melting of a mafic source, such as Archaean tholeiite TH-1 in equilibrium with hornblende-pyroxene-plagioclase restite. Subsequent differentiation of these melts in equilibrium with titanoilmenite-pyroxene-plagioclase cumulate may have given rise to the trondhjemites and rhyolites. Such a mineralogy of the restite and cumulate phases suggests that felsic melts containing little water in the Verkhovtsevo greenstone belt were generated at depths up to 30 km, probably in the greenstone belt's mafic basement. 相似文献
13.
吉林省板石沟—旺文川绿岩带岩石地球化学特征及成岩环境分析 总被引：1，自引：0，他引：1
吉林省南部晚太古宙绿岩带位于龙岗古陆核南部边缘,它包括板石沟、四方山和旺文川绿岩带,其岩石主要为变质镁铁质火山岩和变质长英质火山岩,反映出具双峰式火山岩的特征。另外,本区绿岩带岩石的岩石化学和地球化学特征与龙岗古陆核北部边缘的夹皮沟绿岩带具有明显的差异,表明两者成岩环境不同。本区绿岩带斜长角闪岩属板内玄武岩,其成岩环境与大陆裂谷环境相似。 相似文献
14.
简叙辽东地区太古宙绿岩带地质背景,并结合太古宙绿岩带铁-铀型铀矿成矿地质特征的阐述,提出太古宙绿岩带铀成矿作用具有明显的前寒武纪主期性。讨论太古宙富铀钾质花岗岩相关的太古宙残留体内构造-蚀变岩控制铀矿的观点：提出古韧性剪切-破碎断裂带、太古宙基底岩体顶上凸起带之凹洼中的＂突触＂与碱交代岩等三位一体的构造空间和构造-蚀变岩定位层间-不整合破裂带关联-碱交代热液型铀矿的成矿模式,并且太古宙绿岩带铁-铀型铀矿围岩蚀变清楚,铀成矿谱系反映为初贫后富-叠加再造成矿的矿物组合;以复杂-叠加、脉络清楚的太古宙绿岩带构造环境相关的铀矿聚集区为例,探讨太古宙绿岩带铀成矿作用的多期性。并认为太古宙绿岩带铁-铀型铀矿矿体埋藏深、隐伏性强、盲矿体多,潜在的找矿前景相当可观。 相似文献
15.
Previous models for the temporal evolution of greenstone belts and surrounding granitoid gneisses in the northern Kaapvaal Craton can be revised on the basis of new single zircon ages, obtained by conventional U---Pb dating and Pb---Pb evaporation. In the Pietersburg greenstone belt, zircons from a metaquartz porphyry of the Ysterberg Formation yielded an age of 2949.7±0.2 Ma, while a granite intruding the greenstones, and deformed together with them, has an age of 2853 + 19/−18 Ma. These data show felsic volcanism in this belt to have been coeval with felsic volcanism in the Murchison belt farther east, and the date of 2853 Ma provides an older age limit for deformation in the region. In contrast, a meta-andesite of the Giyani greenstone belt has a zircon age of 3203.3±0.2 Ma, while a younger and cross-cutting feldspar porphyry has an emplacement age of 2874.1±0.2 Ma. The meta-andesite is intercalated with various mafic and ultramafic rocks and, therefore, the age of 3.2 Ga appears plausible for the bulk of the Giyani greenstones.Granitoid gneisses surrounding the Pietersburg and Giyani belts vary in composition from tonalite to granite and texturally from well-layered to homogeneous but strongly foliated. These rocks yielded zircon ages between 2811 and 3283 Ma. The pre-3.2 Ga gneisses are polydeformed and may have constituted a basement to the Giyani greenstone sequence, while the younger gneisses are intrusive into the older gneiss assemblage and/or into the greenstones. The Giyani and Pietersburg belts probably define two separate crustal entities that were originally close together but were later displaced by strike-slip movement. 相似文献
16.
Jean Pierre Nguetnkam Fredéric Villiéras Richard Kamga Georges Emmanuel Ekodeck Jacques Yvon 《Chemie der Erde / Geochemistry》2014
Mineralogy, major, trace and rare earth elements of a weathering profile developed on tertiary greenstone belt in the extreme North Cameroon are reported. The aim of which was to investigate mineralogical evolution and element mobilization and redistribution during weathering under dry tropical climate. The weathering profile consists of four main horizons: (1) a spheroidal weathering zone constituted by a corestone–shell complex, (2) a C horizon, (3) a Bw horizon and an Ah horizon. The results indicate that nontronite, a Fe-rich smectite, is the exclusive clay mineral formed in the exfoliated shells and the C horizon. It is associated with kaolinite in the upper horizons. The coexistence of these two clay minerals induced a decrease of CEC and pH which becomes neutral. The weathering index (WI) values reveal that weathering becomes more and more intensive from the corestone up to Bw horizon, which is the most weathered horizon in the weathering profile. Mass balance calculations, using Th as immobile element, indicate that Ti is quite mobile and that Al and Fe are relatively enriched at the bottom and strongly leached at the top of the profile. Alkalis and alkaline earth elements are strong leached through out the profile, except Ca which displays similar trend as Al and Fe. The same goes for LILE (Cs, Sr), TTE (Cr, Co, Ni) and HSFE (Y, Nb, Hf). In opposite, REE are depleted at the bottom and enriched in the upper horizons, with more enrichment for LREE than for HREE. It appears that weathering of greenstone belt causes a fractionation of HREE and induces a concentration of LREEs. Ce and Eu anomalies display opposite behaviour. 相似文献
17.
格陵兰地质矿产特征及主要金属矿产找矿方向 总被引：1，自引：0，他引：1
格陵兰为前寒武纪地盾区,出露的岩石以片麻岩和上壳岩为主,形成于太古代和元古代一系列碰撞造山环境;在地盾西部、东部和北部边缘广泛发育了元古代一中生代的沉积地层和盆地;岩浆活动贯穿于太占代至新乍代,形成了岩性多样、规模不一的岩浆岩。格陵兰矿产资源丰富,已发现铁、金、铅锌、稀有稀土、铂族、铜、镍等多种矿产资源。分析表明,格陵兰西南部、中西部和北部分布的条带状含铁建造是寻找BIF型铁矿的有利靶区;西南部太古代绿岩带、南部凯蒂利z也活动带具有寻找绿岩带型金矿和造山带型金矿的潜力;西南部碳酸岩、碱性岩岩体是寻找稀有稀土金属矿床的主要靶区;西北和东北部发育的沉积箍地和地层是寻找SEDEX型和MVT型铅锌矿以及砂页岩型铜矿的有利地区;西南和东南部分布的太古代一元占代丛性、超基性岩是寻找铂族元素和镍矿的有利靶区。 相似文献
18.
矿物磁性特征在金矿床形成及成矿预测中的作用 总被引：3，自引：1，他引：2
金矿床形成和成矿预测一直为国内外学者所关注。随绿岩带金矿、暗色岩易富金及赤铁矿总含有大粒金等不断地被发现,指示矿物磁性对金矿床形成有一定的控制作用。1)金粒级的大小与磁体间作用力的强弱呈正比,磁力的大小与两磁体间距离的平方呈反比,这正、反比规律进一步解析绿岩带富金机理和强、弱磁性岩石富金条件的差别。2)电流在金、黄铁矿和磁黄铁矿等附近每一点都能产生磁化场(H场)和磁通密度(B场),H场和B场的大小与不同成矿介质具有一定的正比例关系,按此比例可追踪含矿流体形成过程和富金条件。3)根据矿物磁性特征,建立了矿物磁力晕、矿物磁性矢量等找矿标志。4)除温度和压力等因素外,矿物磁性特征应视为金矿床形成和预测主要条件之一。 相似文献
19.
In central Shikoku, SW Japan, the Mikabu belt is bounded to the north by the Sanbagawa belt, and to the south by the northern (N) Chichibu belt. The N-Chichibu belt can be further subdivided into northern and southern parts. There is no apparent difference in the overall geology, structure, or fossil and radiometric ages between the Mikabu belt and the northern part of the N-Chichibu belt. Greenstones from the Mikabu belt and the northern part of the N-Chichibu belt show evidence for similar low-grade metamorphism, and include the following mineral assemblages with albite+chlorite in excess: metamorphic aragonite, sodic pyroxene+quartz, epidote+actinolite+pumpellyite, glaucophane+ pumpellyite+quartz, and lawsonite (not with actinolite or glaucophane). These similarities suggest that the Mikabu belt and the northern part of the N-Chichibu belt belong to the same geological unit (the MB-NNC complex). The mineral assemblages also indicate that the MB-NNC complex belongs to a different metamorphic facies from the low-grade part of the Sanbagawa belt, that is, the former represents lower temperature/higher pressure conditions than the latter. Structural and petrological continuity between the MB-NNC complex and Sanbagawa belt has not yet been confirmed, but both have similar radiometric ages. It is therefore most likely that the MB-NNC complex and Sanbagawa belt belong to the same subduction complex, and were metamorphosed under similar but distinct conditions. These two units were juxtaposed during exhumation. In contrast, the southern part of the N-Chichibu belt is distinct in lithology and structure, and includes no mineral assemblages diagnostic of the MB-NNC complex and the Sanbagawa belt. Thus, the southern part of the N-Chichibu belt may represent a different geological unit from the MB-NNC complex and Sanbagawa belt. 相似文献
20.
江苏宁芜北段自然重砂异常特征及其对铜金矿的响应 总被引：2，自引：0，他引：2
宁芜火山岩盆地是长江中下游成矿带中重要的铁、硫、铜、金成矿区。基于宁芜北段自然重砂建库数据,通过ZSAPS2.0软件GIS平台,选择与火山热液充填型铜金矿相关的特征矿物,圈定了自然重砂组合异常。通过自然重砂组合异常特征发现,铜矿物(黄铜矿、斑铜矿、蓝铜矿、辉铜矿、孔雀石)、自然金、黄铁矿、重晶石等重矿物组合对火山热液充填型铜金矿响应明显。在组合异常的基础上,圈定自然重砂综合异常,以成矿地质条件、与已知矿床的对应关系、异常强度、异常规模、重砂异常套合程度等为指标,对综合异常进行评价,从而为宁芜火山岩盆地北段铜金矿找矿远景区的划定提供依据。 相似文献