深源富碱热液流体与斑岩铜矿含矿斑岩的成因联系

Porphyry copper deposits are the most important copper type both in China and abroad and their genesis has long been a hot subject that geologists of mineral deposits have studied. The dispute among different academic views has lasted nearly a century, but it has not ceased till now. In this study the authors systematically collected the data about the characteristics of the formation of porphyry copper deposits at home and abroad and different views held by predecessors with respect to their genesis and intensively analyzed the augments, grounds, deficiencies and points at issue for different academic views about the genesis of this type of ore deposits. The emphasis is placed on the temporal-spatial distribution, material components (including isotopes), textures and structures and inclusions in minerals of China's porphyry copper deposits. Study indicates that the distribution of these deposits also shows the stratabound character. They occur in a certain rock formation of a certain age in certain strata of certain areas (appendix 2). Various kinds of phenocrysts (quartz, feldspar, biotite and hornblende) in ore-bearing porphyries have such distinct porphyroblastic textures as mosaic, poikiloblastic, sieve, interstitial, cumulophyric, Blastoclastic and overgrowth textures (appendices 1 and 3). In the phenocrysts melting inclusions are absent or rare, while fluid inclusions are rich. The dominant components of the fluid inclusions are H2O, CO2, K+, Na+, Cl- and SO42-, showing that these phenocrysts have the character of alkali-rich fluid processes. Fluid inclusions in the quartz phenocrysts have the distinct features of the assemblage of saturated and oversaturated saline water-vapor boiling fluid inclusions, suggesting that these fluid inclusions were captured in an "inhomogeneous" phase state; so according to their homogenization temperatures the trapping temperatures of the fluid inclusions, i.e. the formation temperatures of the quartz phenocrysts, may be determined to be in the range of 190 to 407℃. This temperature range is notably lower than the crystallization temperatures (solidus temperatures) of intermediate-acid magmas (appendices 1 and 3). The degree of order of K-feldspar (phenocrysts) is 0.457-0.597 (X-ray diffraction analysis) and 0.64-0.72 (infrared spectrometry); the triclinity is 0.675-0.775 (X-ray diffraction analysis) and 0.17-0.44 (infrared spectrometry); the texture index η is 0.278-0.813-all the three parameters prove that these K-feldspar phenocrysts are all andesine-microcline. Its formation temperatures are < 500℃ and generally range from 360 to 430℃. This temperature range is also markedly lower than the solidus temperatures of intermediate-acid magmas (appendix 6). These data indicate that quartz and feldspar are not the product of direct crystallization of magmas. Isotope data show that the isotopic composition (O, S, H, Sr, C etc.) in most porphyry copper deposits has the character of crustal-mantle mixing (appendix 2). Based on these data the authors propose that porphyry copper deposits mainly originate from metasomatism or partial melting of copper-bearing rocks in the upper crust by deep-seated (mantle or lower crust), alkali (K and Na)-rich siliceous hydrothermal fluids (or mixture of fissure water and groundwater in crustal rocks). This view has both great theoretical and practical significance for the study of the genesis of porphyry copper deposits and prospecting for this type of ore deposits.

研究我国几个主要斑岩铜矿含矿斑岩体的结构构造、物质组分，重点研究斑晶的结构及斑晶中固体包裹体与流体包裹体组分。测定流体包裹体的温压条件，模拟含矿斑岩体形成过程。研究深源热流体的组分、来源及与上地壳岩石相互作用的机理。提出斑岩铜矿的成岩、成矿理论，促进斑岩铜矿的找矿工作具重要意义。