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991.
华南地区中生代Cu (Mo) W Sn矿床成矿作用与洋岭/转换断层俯冲 总被引:25,自引:1,他引:24
华南地区是我国重要的金属矿产资源产地,除了发育大量的钨锡钼铋和稀土等金属矿产外,还有铜金矿床分布。本文通过对华南地区29个典型CuMoWSn矿床的时空分布及其与之有关的花岗质岩体的侵位年龄分析,探讨了与不同成矿类型有关的花岗质岩石的地球化学特征。本文认为华南地区10个典型的与Cu有关的矿床主要发生在180~170Ma、160~150Ma以及105~90Ma三个时期,而10个钨矿床主要集中于170~130Ma;4个WSn矿床集中于170~130Ma和120~110Ma;而5个Sn矿床则发育于170~150Ma、130~110Ma以及100~90Ma三个时期。Cu矿床主要与同熔型花岗岩有关,而Mo、WSn既与同熔型花岗岩有关,又与改造型花岗岩有关。在岩石地球化学上,与Cu(Mo)WSn成矿作用有关的花岗质岩石也表现出不同的地球化学特点,如,从Cu(Mo)矿床到WSn矿床SiO2含量有逐渐增大、氧化性逐渐降低、还原性逐渐增加以及分异演化程度有逐渐增高的趋势。与Cu(Mo)Au矿床有关的花岗质岩石具有较低的SiO2(60.3%~68.1%),氧化性较高(Fe2O3/FeO=0.31~1.81),分异演化程度较低(Rb/Sr=0.05~3.3)的特点;与Cu(Pb)(Zn)矿床有关的花岗质岩石具有相对较高的SiO2(73.3%~75.2%),氧化性稍高(Fe2O3/FeO=0.68~1.74),分异程度稍低(Rb/Sr=10.8~57.8)的特点;而与Mo矿床有关的花岗质岩石具有较宽的SiO2(67.3%~76.2%)变化范围,氧化性稍低(Fe2O3/FeO=0.68~1.74),分异演化程度稍低(Rb/Sr=0.6~9.29);与W矿有关的花岗质岩石的SiO2含量为69.9%~80.1%,还原性稍低(Fe2O3/FeO=0.19~0.76),分异演化程度稍高(Rb/Sr=21.9~61.7);与WSn矿床有关的SiO2为74.8%~78.7%,还原性较低(Fe2O3/FeO=0.08~0.59),分异程度较高(Rb/Sr=10.8~139);与Sn矿床有关的花岗质岩石的SiO2为64.8%~76.9%,还原性高(Fe2O3/FeO=0.01~0.58),分异演化程度高(Rb/Sr=1~530)。在结合华南地区花岗岩类岩石的分布特征以及盆岭构造的特点,本文提出华南地区CuMoWSn矿床的成矿作用是不同时期大洋板块或者洋岭多阶段俯冲结果的新成因模型,即早侏罗世休眠的FarallonIzanagi洋岭俯冲导致早—中侏罗世Cu成矿作用;中—晚侏罗世活动的FarallonIzanagi洋岭和转换断层俯冲是中晚侏罗世Cu(Mo)(W)成矿作用以及多阶段WSn成矿作用的触发动力,而白垩纪Izanagi大洋板块俯冲则是白垩纪斑岩型CuWSn成矿作用的诱因。该模型的提出较好地解释了华南中生代大规模岩石圈拆沉—减薄—伸展的机制及其大规模成矿作用的动力。 相似文献
992.
甘肃玛曲大水金矿矿体地质数据中蕴涵的成矿信息 总被引:3,自引:0,他引:3
大水金矿是著名的超大型矿床,对于其地质地球化学特征已有许多较深入的研究,本文通过单因素直方图统计、关联分析、分形统计、曲线拟合等方法研究了矿体地质数据之间的关系。规模最大的主矿体与其他矿体相比,在顶板围岩、底板围岩、品位、矿体倾向、长度、延深等6个要素上均体现出奇异性,可见主矿体是在十分特殊的地质环境中形成的。控矿变量中,矿体长度、厚度、延深和倾向等变量之间具有相关性,倾向在20°~320°内变化,倾角、品位与其他变量之间的相关性不显著;由此推测,成矿作用的发生并不直接受控于浅层的构造因素,而与岩浆侵入及热液活动诱发的似环状、似锥状局部构造裂隙有关。矿体资源量具有明显的多重分形分布特征,而矿体的长度总体上呈简单分形分布,与前人的研究结果联系起来看,大吨位矿体的围岩以构造角砾岩或蚀变角砾岩为特征,属于充填成因;而中等规模的矿体则属于热液交代成因,一些小规模矿体可能与沉积作用有关;在成矿空间上,不同期次的成矿作用遵循了同位成矿规律。矿床的吨品位关系对幂律分布并不能很好地拟合,而是服从指数分布。 相似文献
993.
New petrographic and fluid inclusion data from core samples of Upper Permian dolomitic limestone (Hauptdolomit, Zechstein group, Stassfurt carbonate sequence) from a gas field located at the northern border of the Lower Saxony Basin (LSB) essentially improve the understanding of the basin development. The gas production at the locality is characterized by very high CO2 concentrations of 75–100% (with CH4 and N2).Samples consist of fine grained, mostly laminated and sometimes brecciated dolomitic limestone (mudstone/wackestone) from the transition zone between the shallow water zone (platform) and the upper slope. The study focuses on migration fluids, entrapped as fluid inclusions in diagenetic anhydrite, calcite, and fluorite, and in syn-diagenetic microfractures, as well as on the geochemistry of fluorite fracture mineralizations, obtained by LA-ICP-MS analysis. Fluid inclusion studies show that the diagenetic fluid was rich in H2ONaClCaCl2. Recrystallized anhydrite contains aqueous inclusions with homogenization temperatures (Th) of ca. 123 °C, but somewhat higher Th of ca. 142 °C was found for calcite cement followed by early Fluorite A with Th of 147 °C. A later Fluorite B preserves gas inclusions and brines with maximum Th of 156 °C. Fluorite B crystallized in fractures during the mobilization of CO2-bearing brines. Crossing isochores for co-genetic aqueous-carbonic and carbonic inclusions indicate fluid trapping conditions of 180–200 °C and 900–1000 bars. δ13C-isotopic ratios of gas trapped in fluid inclusions suggest an organic origin for CH4, while the CO2 is likely of inorganic origin.Basin modelling (1D) shows that the fault block structure of the respective reservoir has experienced an uplift of >1000 m since Late Cretaceous times.The fluid inclusion study allows us to, 1) model the evolution of the LSB and fluid evolution by distinguishing different fluid systems, 2) determine the appearance of CO2 in the geological record and, 3) more accurately estimate burial and uplift events in individual parts of the LSB. 相似文献
994.
铁锰结核结壳生长过程的一种理论假设 总被引:4,自引:0,他引:4
铁锰结核成矿物质的直接来源是大洋底层水和沉积物孔隙水,结壳只有底层水,因此,底层水和孔隙水的物理化学特征就成为理解铁锰结核(壳)成矿作用特征与过程的关键。铁锰结核(壳)内部构造的两个明显特征是:①韵律性的环状纹层构造,和②树枝状构造,这两种构造是典型的远离平衡的非线性地质作用的产物。正常情况下,海底水—沉积物界面系统的底层水、孔隙水中Mn、Fe是不饱和的。因此,铁锰结核(壳)不可能在平衡状态下连续生长。本文提出铁锰结核(壳)生长的自反馈“振荡式”模型。 相似文献
995.
996.
Earlier studies have shown the occurrence of anomalous amounts of methane in rocks associated with lead/zinc mineralization in a number of deposits in the British Isles and Europe. This has led to speculation that the gas may have originated either as a consequence of reactions involved in the mineralization process or as a result of maturation of the organic matter in the sediment or from a deep source. New data are presented showing the distribution of light hydrocarbon gases from fluid inclusions in minerals from the North and South Pennine Orefields which differ from those observed in the host rocks. Possible sources for the gases in the host rocks and the minerals are examined. Based on the close correlation between the distribution of the gases in the carbonate rocks of Northern England and the conodont colour alteration index map for the area, it is suggested that the anomalous amounts of methane gas in the Northern Pennine host rocks are the result of maturation prior to mineralization. The distribution of gases in the fluid inclusions in the minerals serves as a distinguishing feature, and two assemblages are recognized from the South Pennine Orefield, both of which are distinct from that of the Northern Pennines. It is concluded that these gases, trapped at the time of mineralization, originate as a consequence of reactions which occurred during mineral deposition. 相似文献
997.
Xianrong Luo Baohong Hou Meilanna Wen Nanshi Zeng Keeling John Fidler Roger Fabris Adrian 《中国地球化学学报》2008,27(2):198-202
A version of the geoelectrochemical prospecting technique developed in China was demonstrated in China and Australia to test its suitability under both Chinese and Australian conditions. This paper briefly describes the mechanism and effectiveness of the technique applied to search of concealed mineralisation through regolith cover, based on both experimental and field tests. This paer deals with three main aspects of the method: a) how metallic ions are released from orebodies by electrochemical dissolution; b) how these ions migrate to the collector and are deposited as elements by electrochemical extraction in the presence of an electric field; and c) the effectiveness of the method illustrated by some case studies. 相似文献
998.
999.
Temporo-spatial Coordinates of Evolution of the Ordos Basin and Its Mineralization Responses 总被引:2,自引:1,他引:1
LIU Chiyang ZHAO Hongge ZHAO Junfeng WANG Jianqiang ZHANG Dongdong YANG Minghui 《《地质学报》英文版》2008,82(6):1229-1243
The Ordos basin was developed from Mid-Late Triassic to Early Cretaceous, and then entered into its later reformation period since the Late Cretaceous. Its main body bears the features of an intra-cratonic basin. The basin also belongs to a multi-superposed basin which has overlapped on the large-scale basins of the Early and Late Paleozoic. Currently, Ordos basin has become a residual basin experienced reformation of various styles since the Late Cretaceous. It's suggested that there were at least four obvious stages of tectonic deformations existing during the basin's evolution, dividing the evolution and sedimentation into four stages. The prior two stages were of the most prosperous, during which the lake basin was broad, the deposition range was more than twice larger than the current residual basin, resulting in major oil- and coal-bearing strata. The two stages were separated by regional uplift fluctuations in the area. At the end of the Yan'an Stage, the depositional interruption and erosion were lasting for a short period of time. The third one is the Mid- Jurassic Zhiluo-Anding stage, in which the sedimentation extent was still broad but the lake area was obviously reduced. In the Late Jurassic tectonic deformation was intensive. A thrust-nappe belt was formed on the basin's western margin while conglomerate of different thickness were accumulated within the foredeep of the eastern side. The central and eastern parts of the basin were subject to erosion and reformation. A regional framework with "uplift in the east and depression in the west" took shape in the area west of the Yellow River. In the Early Cretaceous sediments were widely distributed, unconformably overlapping the former western margin thrust belt and the ridges on the northern and southern borders. There are abundant energy resources such as oil, natural gas, coal and uranium deposits formed in Ordos Basin. The main stages of generation, mineralization and positioning of the multiple energy resources have obvious responding co 相似文献
1000.
宝清—饶河一带中生代地层中深海相硅质岩和浊积岩分布区的锰元素地球化学异常较多,并发现了一些原岩光谱的高值点和锰矿化线素。加强对本区锰元素化探异常的研究和加大对锰矿的勘查力度就显得尤为重要。 相似文献