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新疆希勒库都克铜钼矿区岩浆混合作用: 来自锆石U-Pb年代学的证据 总被引：7，自引：6，他引：1
新疆北部富蕴县内希勒库都克铜钼矿区的花岗闪长岩及其包体岩相学、矿物化学和岩石地球化学特征及野外地质特征显示其为岩浆混合作用的结果。本文获得花岗闪长岩及其中暗色微粒包体玄武安山玢岩、细粒辉长闪长岩锆石U-Pb年龄为326.8±2.1Ma、327.6±2.4Ma、329.3±2.3Ma,年龄值基本一致,这一结果从年代学角度为花岗闪长岩及其中暗色微粒包体的岩浆混合作用成因提供证据。偏酸性的花岗闪长质与偏基性玄武安山质岩浆混合作用形成了331.9±2.1Ma的安山玢岩脉。 相似文献
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Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (14C) and stable isotope (δ18O and δ13C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core 14C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the 14C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ18O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ13C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns. 相似文献
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Dredging and associated screening at a dredge site in the southern North Sea (Area 408) is associated with areas of well-sorted fine sand that extend for up to 3 km to the south-east of the dredged area and overlay sediments with a more variable particle size composition. This well-sorted fine sand may reflect deposition and transport of material mobilised by the dredging and screening processes at the dredge site. Multivariate analysis of the benthic community structure suggests that marine aggregate dredging, at the level of intensity employed in the study area prior to sample collection, has had a limited impact on benthic community composition compared with that reported from studies elsewhere. This is ascribed to the likely rapid rates of recolonisation by the mobile opportunistic polychaetes and crustaceans that dominate the macrofauna of the sandy gravel deposits at this particular dredge site. Analysis of variance showed, however, that significant differences existed between the sample treatments in terms of species evenness (Pielou's J). Dredged samples were found to have the lowest mean species evenness (0.71) when compared to controls (0.77). The present study highlights the inherent difficulties in the application of general impact/recovery predictions to dredged sites with varying environmental characteristics. 相似文献
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青海锡铁山铅锌矿床硫同位素地球化学研究——深源与海水硫的混合 总被引：5，自引：0，他引：5
锡铁山铅锌矿床发育较为完整的喷流沉积系统,包括管道相、近喷口相、远端沉积相及各种喷流沉积岩,并有后期改造作用形成的脉状铅锌矿体。本文通过喷流沉积系统各部位硫化物硫同位素的分析,不同部位硫化物硫同位素组成不同,且规律性变化。以黄铁矿分析结果为例,网脉状石英钠长岩δ34S=+0.8‰,代表供给系统的硫化物脉2.95‰,非层状矿体4.48‰,层状矿体3.25‰,炭质片岩为+6.26‰,后期改造型铅锌矿脉为+2.93‰。代表管道相的网脉状石英钠长岩黄铁矿具有深源(幔源)的硫同位素组成,而矿体或大理岩上盘炭质片岩具有海水硫来源的特点。矿体的硫介于二者之间,更靠近炭质片岩的硫化物同位素组成,其来源可能更多受海水硫酸盐的制约,即锡铁山矿床硫具有混合来源性质,主要是海水硫酸盐的还原,部分来源于深部卤水的供给。硫的还原方式以生物细菌还原为主。层状矿体中硫同位素组成由早至晚δ34S逐渐降低,表明层状矿体成矿作用过程中,发生了生物成因的H2S的大量加入。 相似文献
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阿尔泰南缘早泥盆世康布铁堡组的SIMS锆石U-Pb年龄及其向东向北延伸的范围 总被引：7，自引：2，他引：5
麦兹火山-沉积盆地康布铁堡组的年龄及其东界,以及阿尔泰南缘早泥盆世火山活动往东往北延伸的范围仍然没有确定;康布铁堡组火山岩的源岩及其形成的构造环境还有待阐明。近年来在麦兹盆地东侧发现了萨吾斯铅锌矿床,矿床赋存于康布铁堡组火山岩,与别斯萨拉玢岩体密切有关。本研究对萨吾斯铅锌矿床的康布铁堡组流纹岩和别斯萨拉玢岩进行了SIMS锆石U-Pb定年以及主微量元素组成测定,以期回答上述问题。流纹岩锆石的18个靶点给出了一致的谐和年龄和加权平均年龄(401Ma);花岗闪长玢岩锆石的15个靶点给出了一致的谐和年龄和加权平均年龄(401Ma)。因此,萨吾斯铅锌矿床康布铁堡组流纹岩和别斯萨拉玢岩是同期喷发/侵入的;康布铁堡组火山活动的时代在早泥盆世;麦兹火山-沉积盆地的东界应抵达卡拉先格尔断裂西侧。在～400Ma时期,阿尔泰地区不仅存在着广泛的花岗岩类深成岩浆活动,也发生了强烈的酸性火山喷发,两者共同构成了阿尔泰南缘的大陆边缘岩浆弧。但是,火山喷发主要集中于阿尔泰南缘,受断裂控制。花岗闪长玢岩的一些锆石给出513.8Ma和3134Ma的U-Pb年龄,反映区内陆壳由寒武纪—奥陶纪岩石组成,并且还有前寒武纪微陆块。硅-碱、SiO_2-K_2O、logτ-logσ、SiO_2-FeO/(FeO+MgO)图以及构造环境判别图表明,萨吾斯铅锌矿床的流纹岩、凝灰岩、石英闪长玢岩-花岗闪长玢岩以及阿尔泰南缘早泥盆世康布铁堡组火山岩形成于活动大陆边缘或岛弧环境。康布铁堡组中下段细碧角斑岩在岛弧海底环境喷发,上段流纹岩喷发于大陆边缘环境。原始地幔标准化的多元素蛛网图表明,萨吾斯矿床的三类岩石具有明显的Nb、Ta、Ti和Sr、P、Ba负异常,显著富集Th、U、K、La、Ce、Pr、Zr、Hf。结合锆石U-Pb年龄,作者认为它们的源岩应以寒武纪-奥陶纪的岛弧岩石为主;同时,可能还含有一定比例的前寒武纪古老陆壳岩石。冲乎尔、克兰、麦兹三个火山-沉积盆地在所属构造单元、陆壳基底、火山岩岩石地球化学以及沉积岩的比例上都表现出系统变化,这些变异控制了阿尔泰南缘块状硫化物矿床从西部到中部到东部的成矿元素组合上的变化。 相似文献
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CuNi-VTiFe复合型矿化镁铁-超镁铁杂岩体岩相学及岩石地球化学特征:以新疆北部为例 总被引：7，自引：4，他引：3
铜镍硫化物矿床和钒钛磁铁矿矿床是镁铁-超镁铁杂岩重要的矿床类型,但二者共生的情况在国内还不多见。新疆北部这类铜镍-钒钛铁复合型矿化岩体较为发育,目前已发现有香山、牛毛泉、土墩南和哈拉达拉等4个岩体属于此类。它们的成岩时代多集中在早二叠世,出露面积在2.8～22km~2,介于通道型铜镍矿化小岩体和大型层状岩体之间,韵律构造发育;岩石组合为超基性-基性-中性岩类,以出现浅色的闪长岩或淡色辉长岩为特点,岩石中金属矿物氧化物(钛铁矿、磁铁矿)和硫化物(黄铁矿、磁黄铁矿、黄铜矿,有时有镍黄铁矿)共存和共生;含矿岩石组合和岩石化学特征与典型铜镍硫化物矿床和钒钛磁铁矿矿床相比,具有重叠和过渡特征;稀土和微量元素特征反映出杂岩体不同岩石类型可能具有相同或相似岩浆来源,是经过强烈分异和演化的产物。新疆北部这类复合型矿化,与北疆地区典型铜镍矿床和典型钒钛磁铁矿矿床,共同构成了新疆北部后碰撞幔源岩浆矿床成矿谱系。 相似文献
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高红移活动星系核的环境是目前亟待研究的领域,与类星体发射线区成协的吸收线系统有可能被使用.为此我们对CIV成协吸收系统进行了统计研究.本文是系列文章的首篇,在本文中我们搜集了87年以前的全部、及87年以后的大部分中、高分辨率CIV吸收线光谱资料,给出了包含228个类星体的均匀无偏统计样本,该样本有CIV吸收线229条,系由228个类星体的所有534条吸收线中选出.此外,我们还定义了4个子样本. 相似文献
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Reflection of Oblique Incident Waves by Breakwaters with Partially-Perforated Wall 总被引：11，自引：6，他引：11
The reflection of oblique incident waves from breakwaters with a partially-perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigenfunction expansion method is applied to expand velocity poten-tials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with experimental data. The effect of porosity, the relative chamber width, the relative water depth in the wave absorbing chamber and the water depth in front of the structure are discussed. 相似文献
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Pollution, turbidity and coral bleaching history, as well as coral diversity, vary along the Tanzanian coastline. Prior to this study, it was not known whether exposure to such environmental variation might have influenced the diversity and distribution of Symbiodinium along this coastline. Such information can provide insight into whether Tanzanian reef-building corals develop adaptation to current trends of climate change. Here, 10 reef-building coral samples were collected from different reefs along the Tanzanian coast with different micro-environments and bleaching histories. The ITS-2 region of ribosomal DNA was employed in the characterisation of Symbiodinium harboured by reef-building corals. DGGE fingerprints and DNA sequences showed that most coral species host a single Symbiodinium type, which is maintained throughout the coast regardless of local environmental differences. We present polymorphic symbioses in Acropora spp., Millepora sp. and Galaxea fascicularis in mainly turbid and warm environments as a sign of adaptation to harsh conditions. However, such adaptation may not provide marked resistance to bleaching because Acropora is a bleaching-susceptible genus. 相似文献