| 莲花山斑岩型钨矿床的氢、氧、硫、碳和铅同位素地球化学 |
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| 引用本文：.1985.Hydrogen, oxygen, sulfur and carbon isotope geochemistry of the Lianhuashan porphyry type tungsten deposit[J].Mineral Deposits,4(1):54~63 |
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| Hydrogen, oxygen, sulfur and carbon isotope geochemistry of the Lianhuashan porphyry type tungsten deposit |
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| Abstract:Located in Mesozoic volcanic rock zone of east Guangdong and associated with Middle Yenshanian subvolcanic rocks. the well-known Lianhuashall por-phyry type tungsten deposit consists of two major ore bodies: one is made up of wolframite-bearing quartz veinlets distributed extensively around both sides of the contact zone and accompanied by biotitization and greisenization, the other is composed of scheelite- and sulfides-bearing stockworks occurring inside the contact zone and accompanied by sericitization, silicification and propylitization. An attempt is made in this paper to investigate the sources of rock-forming and ore-forming materials and water as well as the material exchange between water and rocks in the light of stable isotopes. Rhyolite and quartz porphyry are both characterized by high δO18 values; they have whole rock δO18 values of +10.8‰ and +9.5‰ respectively. Of the deposition stage of wolframite (stageⅡ), δO18H2O values are +10.8-14.0‰, ore-forming temperatures are 350-300℃, calculated δO18H2O values are +3.5- +8.7‰ with a decreasing tendency in upward succession, inclusion water of quartz has δD values from -49 to 60‰, getting higher from great depth to shallow depth, and δO18 values of two wolframite samples are +0.8‰ and +1.4‰ respectively, obviously in unequilibrium state with those of quartz. These data imply that metallogenie water originated from re-epuilibrium magmatic water and that during the deposition of wolframite, these waters mixed with meteoric water, especially at very shallow depths. As for mineraIization stagesⅢand Ⅳ, δO18 values of quartzs vary in a relatively narrow range(+8.8 — +11.0‰); Ore-forming temperatures are from 300℃ to 200℃; equilibrium water hasδOO18 values of -2.4一 +3.7‰; δD values of inclusion water in quartz are -44～-53‰, sIightly heavier than those of the stageⅡ; the whole rockδO18 values of the altered rocks(+6.1—+8.9‰) are generally lower than the values of fresh rocks; calculated W/R ratios axe 0.2—0.7. These data suggest that mineralized water of stages Ⅲand Ⅳis principally meteoric water. It has also been noted thatδD values of Mesozoic meteoric water in the mining area are lower than those of the present surface water by about 20‰, which must have had to do with the fact that in east China, coast line at Mesozoic era lay east of the present coast line. δS34 values of sulfides are -1.1一 +4.5‰; mineral assemblage and tempeture determinations suggest that H2S is the dominant constituent in ore-forming fluids, and the δS34 ∑S values are estimated to be about+3‰; δC13 values of two calcite samples are -6.0‰ and -7.2‰ respectively. These data denote a probable derivation of sulfur and carbon from igneous sources at depth. Isotope composition shows anomalous nature of lead; slope of anomalous lead as obtained by the least square method is 0.1948; when t2=135 m.Y., the calculated t1 is about 2880 m.Y.. This suggests that the Lianhuashan granifolds might have resulted from the anatexis of Precambrian basement rock 2800m. y. age. |
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