埃达克质岩与Cu-Au成矿作用关系的初步探讨
Study on adakitic rock and Cu-Au mineralization.
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摘要: 近来的研究发现，埃达克质岩与Au、Cu、Mo等浅成低温热液矿床及斑岩矿床有密切的关系。我们的研究表明：(1)我国的斑岩铜矿大多与埃达克质岩有关，如德兴、沙溪、多宝山、乌奴格吐山和新近发现的东疆土屋斑岩铜矿等，有些被划归与富碱侵入岩或A型花岗岩有关的斑岩铜矿，如玉龙，也具有埃达克质岩的地球化学特征；(2)华北地区的Au矿床大多与埃达克质岩有关，最典型的如胶东和小秦岭；(3)长江中下游地区的Cu、Au、Mo矿床的岩浆岩大多为埃达克质岩。埃达克质岩与成矿作用之所以密切相关，其原因在于它们在地壳深部形成的条件和环境类似，这就为Au、Cu、Mo等的找矿开辟了一个新的思路。埃达克质岩浆是玄武质岩石在高压、高温和含水条件下熔融形成的，上述条件有利于Cu、Au、Mo等金属元素溶解进入熔体。关于找矿方向，文中指出3点：(1)埃达克质岩发育的地区可能是矿床聚集的地区；(2)与消减作用有关的埃达克岩更有利于成矿元素的富集，对于中国来说，晚元古宙-古生代的古亚洲洋造山带内消减作用广泛发育，有巨大的找矿前景；(3)找矿工作应围绕埃达克质岩体及周围地质体进行。Abstract: Recent work shows that there is a close relationship between adakite and Au-Cu-Mo epithermal deposit and porphyry copper deposits. Our research results obtain following opinions: ( 1 ) most of porphyry copper deposits in China are specially and temporily related to adakites, such as Dexing in Jiangxi, Shaxi in Anhui, Duobaoshan in Heilongjiang, Wunugetushan in Inner Mongolia and Tuwu in eastern Xinjiang. Some of porphyry copper deposits, e. g. , Yulong in Xizang, are originally considered to be related to be hosted by alkaline - rich intrusive rocks or A-type granites, the rocks also have adakitic affinity in geochemistry. (2 ) The gold deposits in the North China are mostly related to adakites, typical cases are those occurred in eastern Shandong Province and Xiao Qinling. (3) The country rocks of Cu-Au-Mo deposits in the middle and lower Yangtze River are mostly adakites. The reason why adakites and mineralization have such a close relationship is that they have similar conditions from the deep crust, which provides a new idea exploring Au-Cu-Mo deposits. Adakitic magma is produced when basalt is partially melted at high - pressure, high - temperature and fluid - rich conditions, which is favorable for metal elements like Cu, Au and Mo to dissolve into melts. The point is the dehydration reaction occurs when hornblende is replaced by garnet during the formation of adakitic magma, which is helpful for the dissolution of Au, Ag, Fe, Cu and Mo from basic rocks and mantle. The regions with adakites development is therefore a potential prospecting area, and the regions occuring slab-related adakite is more favorable for the enrichment of ore-forming elements. So a large potential exploration area in China is the Palaeo-Asian Ocean Orogenic Belt of late Proterozoic-Paleozoic, because subduction was widespread in the belt at that time and future exploration should be fucused on adakites and surrounding geological bodies.
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Key words:
- Adakite /
- Mineralization /
- Metallogenic mechanism /
- Exploration /
- Porphyry copper deposit /
- Epithermal gold deposit
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