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991.
金沙江造山带碰撞后地壳伸展背景——火山成因块状硫化物矿床的重要成矿环境 总被引:18,自引:0,他引:18
近年来对金沙江造山带区域地质、矿床地质和岩石地球化学新资料的研究和典型火山成因块状硫化物(VHMS)矿床的解剖,金沙江造山带的VHMS成矿作用主要发生于早二叠世晚期—晚二叠世海相弧火山岩和晚三叠世裂谷盆地海相火山岩中,构成西南三江地区一条重要的多金属块状硫化物成矿带。成矿带内晚三叠世碰撞后地壳伸展背景下形成的上叠裂谷盆地是其VHMS成矿作用的主体,盆地中火山活动从早期的双峰式火山岩演变为晚期的中酸性火山岩,岩石地球化学特征与孤火山岩有明显的区别,反映其形成于伸展背景。伸展盆地的早期阶段,在双峰火山岩组合的高钾流纹质火山岩系中产出鲁春式VHMS矿床,具有Zn-Cu-Pb-Ag金属组合特征,形成于深水环境;伸展盆地的晚期阶段,在中酸性火山岩系与上覆碳酸盐岩接触带中产出赵卡隆式VHMS矿床,具有Ag-Fe-Pb-Zn金属组合特征,形成于浅水环境;盆地的末期阶段,在滨浅海相磨拉石碎屑岩中产出里仁卡式石膏矿床。金沙江造山带碰撞后地壳伸展背景下VHMS成矿作用的研究,对于造山带中的找矿工作具有重要的指导意义。 相似文献
992.
993.
Methanol masers are known to be associated with regions of massive star formation. By studying the distribution of these masers
with respect to unidentified EGRET sources, one may be able to identify regions of enhanced star formation leading to either
supernova remnants and/or pulsars. In this study, we test for positional coincidences between class II methanol masers and
EGRET sources and determine the statistical significance of these coincidences. 相似文献
994.
Jim Mungall 《中国科学D辑(英文版)》2005,48(6):834-839
There are a lot of mafic and ultra-mafic bodies in the earth,but only a few of them include Cu-Ni-PGE deposits.Of interest has been the formation of such deposits as Cu-Ni-PGE sulfide;especially the separa-tion of sulfide liquid from silicate melts.A lot of re-searcher[1—11]have investigated into the tectonic back-ground of Cu-Ni-PGE deposits,the mechanism of the origin and evolution of magma,and the metal element partition coefficient in sulfide liquid and silicate magma.However,the da… 相似文献
995.
ZHANG Liqiang ZHANG Yan YANG Chongjun LIU Suhong REN Yingchao RUI Xiaoping & LIU Donglin . State Key Laboratory of Remote Sensing Sciences School of Geography Remote Sensing Beijing Normal University Beijing China . State Key Laboratory of Remote Sensing Sciences Institute of Remote Sensing Applications Chinese Academy of Sciences Beijing China . Institute of Geographical Sciences Natural Resources Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(11):2032-2039
Today, with the proposal of digital earth, digital city and digital community, and rapid advances in informa-tion technologies and collection of spatial data, to a great degree, the traditional 2D GIS is promoted to Web and 3D GIS, which greatly challenges the capaci-ties of the system in transmitting and handling massive datasets. A great number of 3D GIS prototype systems have been developed and applied in such areas as mine resource management, digital cities. However, appli-cation sys… 相似文献
996.
Based on structural and mineralogical characteristics of four hydrothermal chimney samples collected by submersible Alvin,
growth history and formation environment of hydrothermal chimney at EPR 9-10°N are established. It is shown that there occur
two types of hydrothermal chimney with different deposition environments at EPR 9-10°N according to differences in their shape,
structure and mineral assemblage: type I chimney forms in an environment with high temperature, low pH and strong reducing
hydrothermal focus flow and type II chimney forms in a relatively low temperature, high pH and rich Zn hydrothermal environment.
Growth of type I chimney begins with the formation of anhydrite. Subsequently deposition of Cu-Fe-Zn sulphide in various directions
of chimneys decides the final structure of this type of chimney. According to observation and analysis of mineral assemblages,
the formation process of type I chimney could be divided into three stages from early, middle to late. Changes of temperature
and major chemical reaction type in the process of hydrothermal chimney formation are also deduced. Different from type I
chimney, quenching crystalline of pyrite and/or crystalline of sphalerite provide the growth foundation of type II chimney
in the early stage of chimney forma-tion. 相似文献
997.
Philip M. Scotney Stephen Roberts Richard J. Herrington Adrian J. Boyce Ray Burgess 《Mineralium Deposita》2005,40(1):76-99
Wetar Island is composed of Neogene volcanic rocks and minor oceanic sediments and forms part of the Inner Banda Arc. The island preserves precious metal-rich volcanogenic massive sulfide and barite deposits, which produced approximately 17 metric tonnes of gold. The polymetallic massive sulfides are dominantly pyrite (locally arsenian), with minor chalcopyrite which are cut by late fractures infilled with covellite, chalcocite, tennantite–tetrahedrite, enargite, bornite and Fe-poor sphalerite. Barite orebodies are developed on the flanks and locally overly the massive sulfides. These orebodies comprise friable barite and minor sulfides, cemented by a series of complex arsenates, oxides, hydroxides and sulfate, with gold present as <10 m free grains. Linear and pipe-like structures comprising barite and iron-oxides beneath the barite deposits are interpreted as feeder structures to the barite mineralization. Hydrothermal alteration around the orebodies is zoned and dominated by illite–kaolinite–smectite assemblages; however, local alunite and pyrophyllite are indicative of late acidic, oxidizing hydrothermal fluids proximal to mineralization. Altered footwall volcanic rocks give an illite K–Ar age of 4.7±0.16 Ma and a 40Ar/39Ar age of 4.93±0.21 Ma. Fluid inclusion data suggest that hydrothermal fluid temperatures were around 250–270°C, showed no evidence of boiling, with a mean salinity of 3.2 wt% equivalent NaCl. The 34S composition of sulfides ranges between +3.3 and +11.7 and suggests a significant contribution of sulfur from the underlying volcanic edifice. The 34S barite data vary between +22.4 and +31.0, close to Miocene seawater sulfate. Whole rock 87Sr/86Sr analyses of unaltered volcanic rocks (0.70748–0.71106) reflect contributions from subducted continental material in their source region. The 87Sr/86Sr barite data (0.7076–0.7088) indicate a dominant Miocene seawater component to the hydrothermal system. The mineral deposits formed on the flanks of a volcanic edifice at depths of ~2 km. Spectacular sulfide mounds showing talus textures are localized onto faults, which provided the main pathways for high-temperature hydrothermal fluids and the development of associated stockworks. The orebodies were covered and preserved by post-mineralization chert, gypsum, Globigerina-bearing limestone, lahars, subaqueous debris flows and pyroclastics rocks. 相似文献
998.
The Canatuan and Malusok massive sulfide deposits are located near Siocon, Zamboanga del Norte, in southwestern Mindanao, Philippines. The Canatuan–Malusok area is underlain by the Jurassic–Cretaceous Tungauan schists, which form much of the Zamboanga Peninsula. The volcanic strata at Canatuan and Malusok can be traced for >7 km along strike and is host to at least three discrete massive sulfide bodies: Canatuan, Malusok and SE Malusok. Basal basaltic andesite volcanic rocks are generally chemically uniform and show only moderate alteration. The massive sulfide deposits occur in overlying rhyolitic to rhyodacitic volcanic rocks that are altered to a schistose assemblage of quartz, sericite, chlorite and pyrite. The alteration is texturally destructive but graded clastic beds are locally observed. Despite tropical saprolitic weathering, four lithogeochemical subunits of the felsic package are identified. Stratigraphic interleaving, however, has made correlation of these units over any significant distance difficult. The sulfide lenses are overlain by a few metres of felsic schists which locally contain manganese-bearing silicates and oxides that serve as a stratigraphic marker. Hangingwall andesitic volcaniclastic rocks are discontinuously preserved, although where present, they consist of regularly bedded mafic volcanic sandstones. The lateral continuity of a manganese-bearing marker and flanking felsic volcaniclastic intervals indicate that locally the volcanic strata form a homoclinal sequence. The Canatuan Au–Ag–Cu–Zn deposit consists of a gossan overlying a massive sulfide lens. The sulfides and gossan are flat lying and hosted within felsic volcanic rocks. The gossan is gold–silver-rich, and was formed by a combination of oxidation and volume collapse of the original sulfide lens. The sulfide minerals present below the current water table, are auriferous massive pyrite with base metal sulfides, with some supergene chalcocite. The transition from gossan to sulfides is very sharp, occurring at the water table. Massive sulfide deposits at Malusok are hosted in the same felsic sequence as Canatuan and they have similar base and precious metal contents. Only limited gossan has been found at Malusok. The bimodal nature of the volcanic rocks at Canatuan, together with their low HFSE contents, near-flat REE patterns and tholeiitic affinities, suggest that they formed in an intra-oceanic arc setting above a depleted mantle source. Mafic and felsic volcanic rocks of similar composition have been recovered from the Tonga-Kermadec and Izu-Bonin-Marianas island-arc systems in the western Pacific. Mafic rocks at Canatuan show no evidence for LILE enrichment that characterizes melts derived from metasomatized mantle under more mature arcs, suggesting that they are the product of a nascent, rather than a mature arc. There is no evidence from the REE, or other incompatible trace elements, that continental crust or evolved arc crust was involved in the generation of the Canatuan-Malusok volcanic rocks. Although it has been proposed that the Zamboanga metamorphic complex comprises microcontinental fragments of Eurasian affinity, our data do not support an evolved crustal setting for the Canatuan-Malusok volcanic rocks, which we suggest were derived from an intra-oceanic arc and subsequently accreted to the eastern Mindanao terrane.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00126-003-0350-7Editorial handling: R.R. Large 相似文献
999.
新疆哈密黄山地区铜镍硫化物矿床的稀土元素特征及意义 总被引:29,自引:9,他引:20
通过对新疆哈密黄山铜镍矿带典型矿床矿石矿物和含矿岩石的稀土元素地球化学研究,发现产于造山带的铜镍硫化物矿床的容矿镁铁-超镁铁质岩具有富水特征,部分硫化物稀土曲线呈特殊的“三重弯曲”模式,反应出由于多种液相(流体和熔体)共存,硫化物熔体中含有大量热液流体,在主成矿期(岩浆熔离期)后逐渐演化出富含气液的成矿流体。本区矿床稀土特征不同于克拉通边缘的铜镍矿床,造成上述热液流体参与成矿的原因在于含矿岩体本身富水,可能与碰撞后富水洋壳的拆沉熔融有关。 相似文献
1000.
The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part I: geology
Hans Årebäck Timothy J. Barrett Stig Abrahamsson Pia Fagerström 《Mineralium Deposita》2005,40(4):351-367
The Kristineberg volcanic-hosted massive sulphide (VMS) deposit, located in the westernmost part of the Palaeoproterozoic
Skellefte district, northern Sweden, has yielded 22.4 Mt of ore, grading 1.0% Cu, 3.64% Zn, 0.24% Pb, 1.24 g/t Au, 36 g/t
Ag and 25.9% S, since the mine opened in 1941, and is the largest past and present VMS mine in the district. The deposit is
hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the Skellefte Group, which forms the
lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits. The Kristineberg deposit
is situated lower in the Skellefte Group than most other deposits. It comprises three main ore zones: (1) massive sulphide
lenses of the A-ore (historically the main ore), having a strike length of about 1,400 m, and extending from surface to about
1,200 m depth, (2) massive sulphide lenses of the B-ore, situated 100–150 m structurally above the A-ore, and extending from
surface to about 1,000 m depth, (3) the recently discovered Einarsson zone, which occurs in the vicinity of the B-ore at about
1,000 m depth, and consists mainly of Au–Cu-rich veins and heavily disseminated sulphides, together with massive sulphide
lenses. On a regional scale the Kristineberg deposit is flanked by two major felsic rock units: massive rhyolite A to the
south and the mine porphyry to the north. The three main ore zones lie within a schistose, deformed and metamorphosed package
of hydrothermally altered, dominantly felsic volcanic rocks, which contain varying proportions of quartz, muscovite, chlorite,
phlogopite, pyrite, cordierite and andalusite. The strongest alteration occurs within 5–10 m of the ore lenses. Stratigraphic
younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration, and
tectonic folding and shearing. In the vicinity of the ore lenses, hydrothermal alteration has produced both Mg-rich assemblages
(Mg-chlorite, cordierite, phlogopite and locally talc) and quartz–muscovite–andalusite assemblages. Both types of assemblages
commonly contain disseminated pyrite. The sequence of volcanic and ore-forming events at Kristineberg is poorly constrained,
as the ages of the massive rhyolite and mine porphyry are unknown, and younging indicators are absent apart from local metal
zoning in the A-ores. Regional structural trends, however, suggest that the sequence youngs to the south. The A- and B-ores
are interpreted to have formed as synvolcanic sulphide sheets that were originally separated by some 100–150 m of volcanic
rocks. The Einarsson zone, which is developed close to the 1,000 m level, is interpreted to have resulted in part from folding
and dislocation of the B-ore sulphide sheet, and in part from remobilisation of sulphides into small Zn-rich massive sulphide
lenses and late Au–Cu-rich veins. However, the abundance of strongly altered, andalusite-bearing rocks in the Einarsson zone,
coupled with the occurrence of Au–Cu-rich disseminated sulphides in these rocks, suggests that some of the mineralisation
was synvolcanic and formed from strongly acidic hydrothermal fluids.
Editorial handling: P. Weihed 相似文献