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961.
在中生代岩浆作用过程主量元素、微量元素和Sr-Nd同位素地球化学演化轨迹的研究基础上,探讨了新路盆地火山岩型铀成矿的深部动力学机制.研究表明,新路盆地由早至晚系列岩浆岩,SiO2含量依次降低,碱度和K2O/Na2O比值逐渐升高,氧化物含量表现为“跳跃性”演变并趋向辉绿岩;ΣLREE、δEu值和Sr元素等含量显著动态升高;微量元素特征比值表现出趋势性变化特点;Sr-Nd同位素演化呈现出由黄尖组熔结凝灰岩依次趋向花岗斑岩、辉绿岩的混合演化趋势线;代表成矿流体同位素组成的萤石投影点位于岩浆作用过程Sr-Nd同位素混合演化趋势线上,且较花岗斑岩更趋近于辉绿岩投影区.认为新路盆地铀矿床成矿流体具有壳幔源区物质混合特征;酸性系列岩浆岩与火山岩型铀矿在空间上的叠置,是壳幔作用机制下系列产物的耦合;来自岩石圈富集地幔的以富含LREE及K、Sr等大离子亲石元素为特征的高温“轻物质流”持续上涌及由此诱发的壳幔作用,为新路盆地岩浆活动及火山岩型铀成矿作用提供了动力学机制;壳幔作用源区是铀成矿作用的动力源,也是成矿流体的发源地. 相似文献
962.
SHRIMP U–Pb zircon ages are reported from a paragneiss, a pegmatite, a metasomatised metasediment and an amphibolite taken from the upper amphibolite facies host sequence of the Cannington Ag–Pb–Zn deposit at the southeastern margin of the Proterozoic Mt Isa Block. Also reported are ages from a middle amphibolite‐facies metasediment from the Soldiers Cap Group approximately 90 km north of Cannington. The predominantly metasedimentary host rocks of the Cannington deposit were eroded from a terrane containing latest Archaean to earliest Palaeoproterozoic (ca 2600–2300 Ma) and Palaeoproterozoic (ca 1750–1700 Ma) zircon. The ca 1750–1700 Ma group of zircons are consistent with sedimentary provenance from rocks of Cover Sequence 2 age that are now exposed to the north and west of the Cannington deposit. The metasedimentary samples also include a group of zircon grains at ca 1675 Ma, which we interpret as the maximum depositional age of the sedimentary protolith. This is comparable to the maximum depositional age of the metasediment from the Maronan area (ca 1665 Ma) and to previously published data from the Soldiers Cap Group. Metamorphic zircon rims and new zircon grains grew at 1600–1580 Ma during upper amphibolite‐facies metamorphism in metasedimentary and mafic magmatic rocks. Zircon inheritance patterns suggest that sheet‐like pegmatitic intrusions were most likely derived from partial melting of the surrounding metasediments during this period of metamorphism. Some zircon grains from the amphibolite have a morphology consistent with partially recrystallised igneous grains and have apparent ages close to the metamorphic age, although it is not clear whether these represent metamorphic resetting or crystallisation of the magmatic protolith. Pb‐loss during syn‐ to post‐metamorphic metasomatism resulted in partial resetting of zircons from the metasomatised metasediment. 相似文献
963.
The first zircon U–Pb SHRIMP dating on high-grade meta-igneous units in the northernmost parts of the Fraser Belt along the southern margin of the Western Australian Yilgarn Craton, reveal crystallisation ages between 1299 ± 10 and 1250 ± 23 Ma. A small number of older xenocrystic zircons, incorporated in some samples, indicate the presence of Late Paleoproterozoic crust in the region. Zircon that crystallised within a melt accumulated in the neck of a boudinaged mafic unit was dated at 1296 ± 4 Ma, indicating that the emplacement of the igneous protoliths took place syntectonically. The anisotropy of magnetic susceptibility of the granulites indicates minimum axes with a mean inclination of 4° towards 130°, corresponding to a nearly vertical southwest–northeast (50–230°) magnetic foliation. This is very close to the structural trend of the Fraser Belt suggesting that the magnetic fabric was acquired syntectonically, during the collision between the Yilgarn and Gawler Cratons. The paleomagnetic data on the granulites overlap with published poles for various 1.2 Ga units in the Albany Belt and the 1.2 Ga Fraser dykes, possibly suggesting that the remanence was acquired during the second stage of the Fraser tectonism. A younger magnetisation component resembles a pole of uncertain age published for Bremer Bay in the Albany Belt. 相似文献
964.
A precise baddeleyite U‐Pb age of 2418 ± 3 Ma is reported for the westerly extension of the Binneringie Dyke in the south‐western Yilgarn Craton of Western Australia. The Binneringie Dyke is a member of the large and extensive Widgiemooltha dyke swarm that trends east‐west across the craton. This age is similar to ages of major dyke swarms In other Archaean Cratons and supports the hypothesis that dykes of the Widgiemooltha swarm are part of a worldwide Palaeoproterozoic mafic magmatic event at ca 2420 Ma. 相似文献
965.
《Australian Journal of Earth Sciences》2013,60(5):769-773
High thorium euhedral, twinned and elongate zircons from the felsic part of a mafic dyke located in the Archaean Yilgarn Craton approximately 30 km northeast of Perth and approximately 2 km east of the Darling Fault, have consistent 207 Pb/ 206 Pb ages of 1214 ± 5 Ma. This age is interpreted as the age of dyke emplacement and is identical, within the uncertainties, with other U–Pb dyke ages reported for the southwest Yilgarn Craton. The present result extends the known occurrence of ca 1210 Ma dykes to the western margin of the Yilgarn Craton and confirms earlier conclusions that a major mafic dyke emplacement occurred throughout the southern Yilgarn Craton during a short‐lived magmatic pulse at ca 1210 Ma. 相似文献
966.
967.
巴音塔拉盆地目前探明的铀矿化主要赋存于赛汉组辫状河道砂体中。通过对含矿主岩的岩性特征、后生蚀变与矿化分析研究,认为该区成矿依靠多期次改造形成的后生蚀变岩以及丰富的含铀、含氧水沿断层渗透还原改造而成矿。 相似文献
968.
华南铀矿成矿年龄统计分析 总被引：3，自引：0，他引：3
华南铀矿分布广泛,铀矿类型包括花岗岩型、斑岩型、火山岩型、碳硅泥岩型和砂岩型,铀矿化通常认为是分期分阶段形成的。本文通过华南130个矿床（点）共361个年龄数据的统计分析,发现铀成矿作用主要发生在145.5Ma以后的中新生代,特别是白亚纪和古近纪。成矿时代具有区域上的同时性,铀成矿作用是一个相对连续的过程。 相似文献
969.
二连盆地马尼特坳陷西部砂岩型铀矿成矿的沉积学背景 总被引：2，自引：0，他引：2
在二连盆地马尼特坳陷西部巴彦乌拉地区,有关赛汉组上段砂岩型铀矿储矿砂体的成因目前存有争议。笔者通过地震剖面、钻孔岩心分析和砂分散体系制图,对赛汉组上段进行了成因分析。研究发现,赛汉组具有特征的断坳转换期构造背景并由此决定了其优质铀储层的发育;赛汉组上段并非传统认识上的纵向辫状河成因,而是剥蚀残留的多个侧向上源自巴音宝力格隆起物源区的辫状河三角洲体系的集合体;构造反转和剥蚀作用对赛汉组地层进行了强烈改造,辫状河三角洲遭受强烈剥蚀,保存了具有多个朵状分割性的带状砂体,形成构造天窗和氧化带并发育铀矿化;砂体的平面非均质性控制了铀成矿作用,砂分散体系的变异部位、沉积相变部位是成矿的有利区域。 相似文献
970.