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1.
Geochemical and isotopic investigations have been carded out on the Chebu gabbroite in southern Jiangxi Province, southeast China and these results are compared with gabbro bodies along the coast of Fujian Province in order to understand their magma sources and tectonic implications. The Chebu intrusion formed at the beginning of the Middle Jurassic (172~4.3 Ma). These rocks are Ti-rich and Al-poor in major elements, characterized by strong enrichment in large-ion lithophile elements (LILE) and moderate enrichment in high field strength elements (HFSE) and light rare-earth elements CLREE), without pronounced Nb or Ta anomalies. Age-correlated Sr-Nd isotope ratios show moderately high ranges of (^87Sr/^86Sr)i from 0.7065 to 0.7086 and 0.5124 to 0.5125 of (^143Nd/^144Nd)i. The geochemical characteristics of the Chebu gabbroite suggest that it is notably different from island-arc basalt and similar to intra-plate basaltic rocks. By combining interpretations of its geological and geochemical characteristics and the regional geological development history, the Chebu gabbroitic intrusion is thought to be the product of asthenosphere upwelling and rapid lithosphere extension during a transition of tectonic systems in southeast China. The tectonic environment and source characteristics of the intrusion are different from Cretaceous gabbro bodies along the coast of Fujian Province, The former formed in a tectonic environment of rapid intra-plate lithospheric extension and the source characteristics were of a weakly enriched primitive mantle, whereas the latter originated mainly in a volcanic-magmatic arc extensional tectonic environment and the nature of the source was an enriched mantle with more subduct subducted components.  相似文献   
2.
There are giant mineral deposits, including the Jinding Zn-Pb and Baiyangping Ag-Co-Cu, and otherimportant mineral deposits (e.g., Baiyangchang Ag-Cu, Jinman Cu deposits, etc.) in the Lanping Mesozoic-Cenozoic Basin, Yunnan Province, China. The tabular ore-bodies and some veins hosted in terrestrial clastic rocks of the Mesozoic-Cenozoic age and no outcropping of igneous rocks in the giant deposits lead to the proposal of syngenetic origin, but the giant mineral deposits are not stratabound (e.g. MVT, sandstone- and Sedex-type). They formed in a continental red basin with intense crust movement. The mineralization is controlled by structures and lithology and occurs in different strata, and no sedimentary nature and no exhalative sediments are identified in the deposits. The deposits show some relations with organic matter (now asphalt and petroleum) and evaporates (gypsum). The middle-low-temperature (mainly 110℃ to 280℃) mineralization took place at a depth of about 0.9 km to 3.1 km during the early  相似文献   
3.
Individual grains of zircon from the Archean Kostomuksha, North Karelian and Matkalakhta greenstone belts, which are situated respectively in western, northern and eastern Karelia, are studied using the ion microprobe SHRIMP II. As a result, the oldest 207Pb/206Pb ages of 3151 ± 4.6 and 3329 ± 16 Ma are first determined for detrital zircons from northern and eastern Karelia. The 207Pb/206Pb ages estimated for two subsequent metamorphic events of Archean Eon in eastern Karelia correspond to 3.25 and 3.17–3.10 Ga. The age value of 2711 ± 9.6 Ma is determined for silicic volcano-plutonic complex and quartz stockwork in northern Karelia and the date 2821 ± 15 Ma for magmatic rocks of eastern Karelia. Silicic volcanics from an oceanic plateau section in the Kostomuksha belt are dated at 2791.7 ± 6.1 Ma for the first time in the Archean of Fennoscandia. The oldest detrital zircons from siliciclastic metasediments determine the stabilization time of Archean continental nuclei in East Fennoscandia. The younger generation of greenstone belts is exemplified in the Karelian craton by the Matkalakhta and Kostomuksha structures comprising rock associations less than 2.82 Ga old, mafic rocks of the Kontokki Group included. Geological history of these belts corresponds to geodynamic mesocycle 90–110 Ma long and to the Archean global epoch of metallogeny, which was responsible for origin of most valuable deposits of base and precious metals.  相似文献   
4.
中国中、新生代含油气盆地构造和动力学背景   总被引:37,自引:4,他引:33  
中国有大约26个含油气盆地。盆地主要有两种类型:(1)伸展盆地;(2)前陆(或挠曲)盆地。第一种伸展盆地主要位于东部,第二种前陆盆地主要位于中部和西北地区。本文讨论了伸展和前陆盆地的以下特征:(1)沉降史;(2)热史;(3)构造样式和运动学。结合深部地球物理和火山岩资料,确定了盆地的地球动力学背景,并且推测盆地形成与西太平洋板俯冲作用和特提斯洋闭合有关。  相似文献   
5.
现代金矿成矿理论的若干进展   总被引:2,自引:0,他引:2  
近十余年来,现代金矿成矿理论研究取得了长足进展,总结这些进展有助于开阔金矿研究和勘查思路。深入地研究了地球动力学背景对金矿成矿的控制,建立了区域成矿学的基本理论,提出了造山带型金矿的概念。岩浆热液和变质热液成矿理论获得了新的证据,在金矿成矿作用过程中岩浆流体较普遍存在,变质去挥发分作用所产生的大量热液是金矿成矿所需的低盐度流体。全球超大型金矿以中温热液型、浅成火山热液型金矿及砂金矿最为多见。从成矿系列理论发展到成矿系统理论,强调了金与其他矿产资源之间的相互联系,提出了铁氧化物型铜一金矿床和钨一锡成矿省内与侵入体有关的2种新类型金矿床。提出金的宇宙来源及撞击成矿理论。  相似文献   
6.
近年来,有关中国东南部中新生代地球动力学背景的研究已取得了重要的进展,主要体现在:地幔性质、岩石圈减薄、岩石圈伸展和构造背景四个方面。研究表明,中国东南部中新生代的地幔性质主体是亏损地幔和EMⅢ型富集地幔混合,中生代以富集地幔为主,而新生代主体为亏损地幔。中国东南部晚中生代经历了岩石圈减薄,并伴生了玄武质底侵作用,具有较为复杂的岩石圈增生~减薄过程。大量事实表明中国东南部中新生代存在多期岩石圈伸展事件,侏罗纪存在局部岩石圈伸展,主要集中于内陆地区,白垩纪经历了区域性岩石圈伸展。近二十年来,中国东南部大规模岩浆的构造背景一直存在着争论,焦点在于太平洋俯冲对中国东南部产生什么的影响。从目前已有的资料来看,白垩纪地幔源区受到太平洋俯冲的影响,太平洋俯冲和玄武质岩浆底侵诱发了地壳加厚,岩石圈拆沉和软流圈上涌而导致岩石圈伸展是中国东南部主要构造背景。但是,中国东南部晚中生代以来的岩石圈伸展—减薄及其深部动力学机制是目前急需进一步深入探讨的问题。  相似文献   
7.
Affected by the compressive stress from the South-Central (Indo-China) Peninsula, the Indosinian orogenesis, characterized by collision, thrust and uplifting, took place inside the South China Plate during 250-230 Ma. The ages of the Indosinian granitoids in the Nanling Range and vicinity areas are mostly 240-205 Ma, indicating that they were emplaced in both late collision and post-collision geodynamic environments. No important granite-related metallogenesis occurred in this duration. A post-orogenic setting started at the beginning of the Yanshanian Period, which controlled large-scale granitic magmatism and related metallogenesis. This paper makes the first attempt to divide the Yanshanian Period into three sub-periods, i.e. the early, middle and late Yanshanian Periods, based mainly on the features of magmatism, especially granitoids and related metallogenesis and their geodynamic environments. The magmatic association of the Early Yanshanian (about 185-170 Ma) comprises four categories of magmatism, i.e. basalt, bimodal volcanics, A-type granite and intraplate high-K calc-alkaline (HKCA) magmatism, which indicates an extension-thinning of lithosphere and upwelling of mantle material to a relative small and local extent. Pb-Zn, Cu and Au mineralizations associated with HKCA magmatism represents the first high tide of Mesozoic metallogenesis in the Nanling Range area. During the middle Yanshanian, the lithosphere was subjected to more extensive and intensive extending and thinning, and hence mantle upwelling and basaltic magma underplating caused a great amount of crust remelting granitoids. This period can be further divided into two stages. The first stage (170-150 Ma) is represented by large-scale emplacement of crust remelting granites with local tungsten mineralization at its end. The second stage (150-140 Ma) is the most important time of large-scale mineralizations of non-ferrous and rare metals, e.g. W, Sn, Nb-Ta, Bi, Mo, Be, in the Nanling Range area. The late Yanshanian (140-65 Ma) was generally characterized by full extension and breakup of the lithosphere of South China. However, owing to the influence of the Pacific Plate movement, the eastern part of South China was predominated by subduction-related compression, which resulted in magmatism of calc-alkaline and shoshonite series and related metallogeneses of Au, Ag, Pb-Zn, Cu and (Mo, Sn), followed by extension in its late stage. In the Nanling Range area, the late Yanshanian magmatism was represented by granitic volcanic-intrusive complexes and mafic dikes, which are genetically related to volcanic-type uranium and porphyry tin deposits, and the mobilization-mineralization of uranium from pre-existing Indosinian granites.  相似文献   
8.
The following geochemical types of granitoids have been investigated in the Mongol-Okhotsk belt:tholetitic,palingenic calc-alkaline,latitic,plumasitic and arpaitic rare-metal granites.Plagiogranites of the tholeiitic series occur within the Mongol-Okhotsk suture,indicating a subduction environment.The calc-alkaline granitoids responsible for the batholith-like intrusions and their formation are related to collision environments.The latest granitoids of the latite series and rare-metal granites came into existence after the collision of continental masses,providing evidence of intraplate magmatism.  相似文献   
9.
大兴安岭中南段铜矿成矿背景及找矿潜力   总被引:17,自引:4,他引:13       下载免费PDF全文
大兴安岭中南段主要铜矿类型为斑岩-热液脉型,其成矿与燕山早期浅定位中酸性侵入体有成因联系,成矿时代集中180Ma ̄160Ma,与中生代早期岩石圈伸展背景下幔源岩浆底侵-同熔-分异作用有关,由于其形成于区域大规模火山喷发之前,深部岩浆来不及进行彻底分异,对铜的大规模成矿不利。因此,寻找大型以上规模的铜矿床必须综合考虑岩浆条件和矿源层两个主要因素。本区大规模岩浆作用晚期(燕山晚期)形成的紫金山式铜矿应  相似文献   
10.
文章通过对大量前人构造地质学、同位素年代学等多元信息资料的分析,认为胶东中生代花岗岩和大型-超大型金矿床形成于华南-华北克拉通后碰撞挤压和伊泽奈崎板块快速斜冲剪切的双重构造环境及其后的拉张构造环境。胶东大型-超大型金矿床受控于经历了韧-脆性剪切、挤压-拉张复杂变形叠加的大型构造岩带,同时也受控于被断裂叠加的花岗岩接触带。根据铅、硫等同位素组成特征及地质构造环境的综合分析,认为成矿物质主要来自以太古宙胶东岩群绿岩和深成岩组成的结晶基底,不排除煌斑岩浆带来部分深源物质;根据流体包裹体的氢、氧、碳同位素组成,判断成矿流体为大气水和岩浆水的混合流体;成矿条件为中低温(380~100℃),低压(86~5.4MPa);成矿时代为燕山晚期(125~100Ma),成矿与燕山晚期拉张环境下的岩浆活动有成因联系,属环太平洋成矿带中温热液金矿床。  相似文献   
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