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1.
The Ogcheon metamorphic belt in central Korea has been interpreted to be the eastward extension of the Nanhua Basin (aulacogen) of southeast China. In this paper, comparisons are made between the two regions based on stratigraphic, thermal-tectonic and other considerations. From this comparison, correlation of geological events between the Nanhua Basin and Ogcheon metamorphic belt are at best equivocal. The closest similarity is the presence in both regions of two major diamictite units, of glacial origin and Neoproterozoic age (750–690 Ma range) in China but of controversial origin and uncertain age in Korea. Volcanic rocks in both regions appear to have similar petrological and geochemical traits and are interpreted to be rift-related. However, their ages are different, mostly 795–780 Ma in the Nanhua Basin and c. 750 Ma in central Korea, so correlation remains uncertain. More isotopic data from both regions may shed light on this comparison. Correlation between other pre-Carboniferous stratigraphic units in the two regions is hampered by the uncertainty about the stratigraphic age and succession in the Ogcheon metamorphic belt, stemming mainly from the absence of fossils and the strong tectonic–metamorphic overprint. Both regions appear to have undergone deformation and metamorphism during the Middle Triassic (Indosinian, Songrim), in some uncertain way related to the collision between the North and South China plates. In the Ogcheon metamorphic belt, there has been no confirmation of a Mid Palaeozoic event, but in the Nanhua Basin that event is recorded by stratigraphic and palaeogeographic evidence. In the Nanhua Basin, there is no evidence for an Early Permian metamorphic event that appears, on isotopic grounds, to have affected the Ogcheon metamorphic belt. This apparent difference has been interpreted as a result of diachronous deformation during Late Palaeozoic–Early Mesozoic plate collisions that took place earlier in the east, in Korea, than in the west in China. 相似文献
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鄂尔多斯盆地北部砂岩型铀矿直罗组物源分析及其铀成矿意义 总被引：4，自引：0，他引：4
鄂尔多斯盆地北部直罗组原生灰色砂岩具有高铀背景值的特征,在层间氧化阶段砂岩同沉积期富集的铀元素遭受氧化迁出构成该区铀成矿的重要铀源。本文对鄂尔多斯盆地北部铀矿区直罗组砂岩进行了碎屑锆石U-Pb定年、重矿物和古水流分析,深入分析了该区直罗组的沉积物源,并探讨了富铀砂岩的成因。结果显示:矿区直罗组砂岩碎屑锆石U-Pb年龄主要集中在251~308Ma,322~354Ma,1529~2182Ma,2200~2632Ma四个年龄区间;富Mn钛铁矿、锆石、磷灰石和榍石的重矿物组合指示物源主要为中酸性岩浆岩;通过与源区对比分析认为铀矿区直罗组物源主要来自盆地之北的乌拉山—大青山地区和狼山东部地区的新太古代、古元古代和晚古生代中酸性岩浆岩及新太古代、古元古代变质岩。结合源区岩体铀含量特征分析,发现晚古生代中酸性岩浆岩相对于源区其它岩体强烈富集铀元素,是研究区直罗组高铀背景值砂岩形成发育的主要原因。晚古生代中酸性岩浆岩的形成与古亚洲洋的演化密切相关,其分布特征可以作为中东亚成矿域内盆地铀资源远景预测的重要依据。 相似文献
3.
We investigated the Jurassic Daebo and Cretaceous Bulguksa granitic rocks in South Korea. The former are distributed mainly in the Gyeonggi and Yeongnam massifs and the latter are present in the Gyeongsan basin and Ogcheon belt. The Daebo granitic rocks generally are of ilmenite series and I to S type. These rocks are associated with Au–Ag hydrothermal deposits, whereas the Bulguksa granitic rocks are of magnetite series and I type, and are associated with Pb–Zn, Cu and Mo–W hydrothermal deposits, as well as Au–Ag hydrothermal deposits. The Daebo granitic rocks show adakitic signatures in their chemical compositions. They are considered to have been derived from partial melting of the thick lower continental crust. Conversely, the Bulguksa granitic rocks in the Gyeongsan basin are non‐adakitic and are considered to have been derived from partial melting of a mantle wedge. Magmas of the Daebo granitic rocks formed at relatively shallow levels, but solidified at deep levels compared with those of the Bulguksa granitic rocks. The Bulguksa granitic rocks in the central to western Ogcheon belt are considered to have been formed by fractionation of magmas derived from partial melting of continental crust. The total Al contents of biotite and hornblende in the granitic rocks increased, with the Bulguksa granitic rocks in the Gyeongsan basin < the Bulguksa granitic rocks in the Ogcheon belt and Gyeonggi and Yeongnam massifs and the Daebo granitic rocks in the Ogcheon belt < the Daebo granitic rocks in the Gyeonggi and Yeongnam massifs. This order corresponds to an increase in solidification depth. 相似文献
4.
河草坑铀矿田位于大富足岩体北西部接触带附近,构造、岩浆及热液活动强烈,发育多种类型的铀矿床、矿点及放射性异常点带.其中发育在花岗岩外带含碳变质岩中的岩浆热液型铀矿,以及发育在花岗岩内带的岩浆热液叠加氧化淋滤而成的复成因铀矿,是今后的找矿目标类型. 相似文献
5.
Hassan Abd El-Razek Aly Shahin 《Arabian Journal of Geosciences》2013,6(7):2245-2259
Optical microscopy, X-ray diffraction (XRD), and back-scattered electron imaging (BSE) have been used to determine the mineralogical composition of the uraniferous iron and manganese oxides and the associated U-minerals hosted in biotite granite that occurred north east Gabal El Sela area south Eastern Desert, Egypt. These mineralizations were found as veinlets fractures filling associated with strongly kaolinitic alteration of the coarse-grained biotite granite. XRD determined that the geothite mineral form the main constituent of uraniferous iron oxide in addition to tapiolite, and kaolinite minerals, where as uraniferous manganese oxide composed of pyrolusite, ramsdellite, and cryptomelane. BSE confirmed that the associated uranium minerals represented by uranothorite, kazolite, and zentime in addition to columbite-bearing minerals. Uranothorite and columbite-bearing minerals are the most abundant minerals in this mineralization. Petrographically, biotite granite is composed mainly of quartz, in addition to K-feldspars, biotite and muscovite with minor zircon, garnet, apatite, uranium-rich thorite and iron oxide. Petrochemical studies and tectonic discrimination diagrams for this granite reveal that they are classified as granite to alkali feldspar granite, originated from calc-alkaline magma having peraluminous nature and developed in within-plate tectonic environment. Field radiometric measurements revealed the localization of two high radiometric anomalies associated with iron and manganese oxides, within this anomaly uranium content range from 65 to 85 ppm. Alpha Track-etch Detectors of radon gas registrations revealed high track density reach up to 15,448.7 Bq/m3. 相似文献
6.
毛洋头火山岩铀（银、钼）矿床的控矿因素及成因 总被引：6，自引：1，他引：6
毛尖头铀矿床，是产于早白垩世晚期火山中的火山岩型矿床。基底构造和岩浆活化对矿床的形成起明显的控制作用，研究认为，该矿床成矿热液早期为岩浆水，晚期为大气降水；成矿元素Ｕ，Ａｇ，Ｍｏ有不同来源；其中早期矿化热液中的铀主要来自次火山热液或次火山岩，而晚期成矿热液的铀主要来自基底岩石； 相似文献
7.
喜峰口-叨尔登金成矿带上的金矿床产出空间各不相同,矿床的围岩有花岗岩、变质岩及沉积岩.矿体的分布均受控于断层破碎带,矿床成因与热液有关.通过对铅、硫以及包裹体水同位素的研究,确定了金矿在成矿时间上与燕山期花岗岩一致,成矿热液中的水主要来源于花岗岩,成矿物质黄铁矿中的硫来源于花岗岩.因此说明研究区的金矿为燕山期花岗岩期后热液成因.产于地壳深部的富含成矿物质的花岗岩浆在上侵过程中同化了部分太古宙变质岩并从中汲取了成矿物质,将其带到地壳浅部,最后沿构造裂隙充填成矿. 相似文献
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10.
《Chemical Geology》2003,193(1-2):81-92
We report Pb–Pb whole rock and uraninite CHemical Th–U–total Pb Isochron MEthod (CHIME) ages of carbonaceous black slates from the Ogcheon metamorphic belt, South Korea. The Pb isotopic data of whole rock samples yield 207Pb/206Pb ages of 283±33 and 291±13 Ma for two outcrops from the northeastern part of the belt. The uraninite CHIME age is estimated at 283±26 and 281±27 Ma for the northeastern and the middle part of the belt, respectively. All of the above ages are identical within error ranges, and represent the timing of peak metamorphism after the late Precambrian intraplate rifting. On the other hand, the 207Pb/206Pb whole rock age for the southwestern part of the belt is estimated at 194±27 Ma, probably representing the timing of contact thermal metamorphism associated with the intrusion of Jurassic granitic plutons. Rb–Sr isotopic data of the black slates do not define any meaningful isochron. The early Permian metamorphic age of this study does not support any tectonic scheme in favor of major tectonometamorphism at either the Silurian–Devonian or the Triassic time. Instead, it corroborates the probability that the two zones in the Ogcheon belt, the Ogcheon metamorphic belt and the Taebaegsan zone, were separated from each other before the development of major structural framework in the former. Our data do not support an idea that the Ogcheon belt corresponds to the continuation of the Triassic collision belt in east central China. 相似文献
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热液矿床石英铅同位素组成及其地质意义 总被引：1，自引：0，他引：1
作者以若尔盖铀矿床为例，研究了含矿热液形成的石英脉石英的铅同位素组成，并将其作为联系母源铅同位素组成的桥梁，判别铀的来源。结果表明，矿床中石英铅同位素组成与含矿黄铁矿和中酸性构造－岩浆成因的花岗岩铅同位素组成具线性演化关系。由此提出含矿热液中的铀来自中酸性构造－岩浆岩而不是地层岩石的新见解，同时提出利用热液石英铅同位素组成判别非放射性矿床成矿元素来源的可能性。 相似文献
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14.
Metamorphic K-feldspar was found in the low-grade pelitic rocks from the Ogcheon metamorphic belt in South Korea. It occurs as extremely fine-grained crystals (5-15 mm in width and 15-25 mm in length) closely associated with fine-grained muscovite and biotite. Their micro structural relations by X-ray mapping analyses using an electron-probe microanalyzer strongly suggest that K-feldspar has grown directly from the matrix phases as a stable phase coexisting with muscovite and biotite during the Ogcheon metamorphism. The phengite component in muscovite indicates about 4.2 kbar at 400°C, suggesting intermediate P/T type of metamorphism. Muscovite separates of two size fractions, 2-4 and 4-8 mm, give K-Ar ages of 153.4±3.3 and 156.7±3.4 Ma, respectively. The biotite separate is 156.5±3.3 Ma in age. Coarse-grained biotite crystal (ca. 0.5 mm) often occurs and it was analyzed by 40Ar/39Ar method using a laser probe step heating technique. It gives a plateau age of 158.2±0.5 Ma that is the same as the K-Ar muscovite and biotite ages. These data, including the previous works, suggest that intermediate P/T type of Ogcheon metamorphic belt exhumed in Middle Jurassic with the dextral strike-slip fault movement. 相似文献
15.
福建浦城毛洋头铀矿床地质特征与找矿前景 总被引：1，自引：0，他引：1
浦城毛洋头铀矿床产于福罗山—大坑火山盆地内,盆地基底为上元古界麻源群大金山组变质岩系和燕山早期高溪复式花岗岩体。受断裂控制,矿体形态复杂,矿体群带具有向主干断裂侧伏,同时又向火山通道中心侧伏的"双侧伏"特点。中酸-酸性火山岩是有利的铀源层,构造产状变异部位、不同岩性接触界面,为铀成矿的有利富集地段。 相似文献
16.
J. Sen N. Ranganath Y.V. Rathaiah D. B. Sen S. N. Kak 《Journal of the Geological Society of India》2009,74(5):639-645
During radiometric investigation at Mawlait, significant uranium mineralisation (0.024–0.22%U3O8) was located mainly within the small pegmatite (garnet bearing quartzofeldspathic rock), which are locally segregated within
migmatite at Umiang River section. Pink granite and granite gneisses are the dominant lithounits of the study area showing
fertile character and spotty radioactivity at several places. Radioactivity in these rocks is mainly contributed by discrete
uraninite grains along with some zircon and xenotime. Granites are peraluminous, low-Ca in nature and their geochemical signatures
suggest derivation from a felsic source. Discriminant diagrams using Rb, Nb and Y indicate ‘within plate’ to ‘volcanic arc’
nature of the rock. The uraniferous pegmatitic veins within migmatite appear to have formed due to localised metamorphic segregation
during late stage of anatexis. Petromineralogical and geochemical studies suggest that the uranium mineralisation in granitic-pegmatitic
rocks of the area is mainly syn-magmatic type. 相似文献
17.
《Chemie der Erde / Geochemistry》2021,81(1):125677
The Lagoa Real uranium (U) province, referred to as Lagoa Real, is located in the state of Bahia, north-eastern Brazil. Lagoa Real has ∼112,000 metric tonnes and average grade of 2700 ppm of U3O8, being one of the largest U deposits in the world and the largest in Brazil. Despite its economic and strategic importance, there are gaps in the geological knowledge of the Lagoa Real U deposits. One of them is the lack of extensive whole-rock chemical data sets. Here, we present whole-rock chemical analyses for major and trace elements, including the rare-earth elements (REE), from barren country rocks to uraniferous ore shoot, systematically sampled from an exploratory drill hole. The chemical data indicate that albitite rocks, with and without uraniferous mineralisation, cannot result from sodic syenitic magmatism, as proposed by recent studies. Petrographical and geochemical evidence supports the previously suggested concept that the Lagoa Real albitite rocks resulted from sodic metasomatism of the granitic country rock, known as the São Timóteo granite. Their ore-mineral assemblages and geochemical characteristics are similar to albitite-hosted U deposits worldwide. 相似文献
18.
华北克拉通西部陆块阴山地块花岗-绿岩带中出露的花岗岩类型比较复杂,研究其类型、成因及其与绿岩带之间的联系,对于探讨花岗-绿岩带的形成和演化有重要意义。本文对内蒙古三合明铁矿西侧红山子地区的花岗-绿岩带进行了研究。其不仅包含有大量的变质科马提岩、科马提质玄武岩和拉斑玄武岩等绿岩带的表壳岩,而且发育着多种变质侵入岩。研究表明,区内与绿岩带相关的侵入岩主要有3种,即变质英云闪长岩、变质花岗闪长岩、变质花岗岩,本文对其中的变质英云闪长岩和变质花岗岩两种岩石进行了地球化学和锆石测年的研究。变质英云闪长岩是一套富铝、低钾、贫铁镁和稀土元素强烈分异的太古宙高铝型TTG岩,SHRIMP锆石U-Pb测年为(2 534±7)Ma(MSWD=1.3),与研究区南部的赞岐岩和TTG的年龄相同;而变质花岗岩具有高硅、富碱,低铁、镁、钛、锰的特点,是一套钙碱性的过铝质岩石,SHRIMP锆石U-Pb测年为(2 509±7)Ma(MSWD=1.5),野外地质现象表明变质花岗岩明显地侵入到区内的绿岩地层和变质英云闪长岩之中。研究发现变质英云闪长岩形成于板块俯冲时TTG岩系岩浆弧构造环境,而变质花岗岩成因则可能与加厚地壳中变沉积岩的熔融有关。 相似文献
19.
本文从变质岩带的含铀性分析入手,研究了赣中变质岩带中铀矿化与变质岩带的含铀性、构造岩浆活动带、变质岩带出露的动力学机制及变质核杂岩构造的关系。研究表明:铀成矿与构造岩浆活动带以及地壳减薄、地幔上隆和在变质核杂岩边缘沿着低角度正断层的地壳伸展构造有着实质的关系。 相似文献
20.
连山关地区下元古界中混合交代作用与铀成矿的关系 总被引：1，自引：0，他引：1
连山关地区在大地构造位置上,处于华北地台东北部营口—宽甸台隆与太子河台凹的过渡部位。前寒武纪地层在本区形成一短轴复背斜构造,轴向290°。背斜轴部由混合花岗杂岩体及呈残留体分布的鞍山群组成,四周为下元古辽河群所包围。背斜北翼有大面积上元古界及下古生界分布(图1)。近年来,在下元古界浪子山组底部与太古界基底混合杂岩体的不整合面附近发现了铀矿床。铀矿床主要赋存在浪子山组沉积变质岩及白色混合岩中。其形成 相似文献