| 中国东部地壳成分的不均匀性及矿床的亲缘性 |
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| 引用本文：陈廷愚.1984.中国东部地壳成分的不均匀性及矿床的亲缘性[J].地球学报,6(2):211-223. |
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| 摘要点击次数: 1989 |
| 全文下载次数: 1879 |
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| 中文摘要:<正> 矿床分布的一个显著特点就是它的不均匀性。长时期以来,为了寻找矿床分布的规律,人们从岩浆作用、火山活动、热液活动、沉积作用、变质作用以及构造运动等方面进行了大量工作,获得了重要成果。但是,随着研究的深入,人们发现,从一个地区得出的规律,并不总是能够应用于另一个地区。例如,相当长时间以来,为了寻找中酸性岩浆作用与成矿的关系,人们做了大量的岩石化学工作,进行了有益的探索。 |
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| HETEROGENEITY OF THE CRUSTAL COMPOSITION AND CONSANGUINITY OF MINERAL DEPOSITS IN THE EASTERN PART OF CHINA |
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| Abstract:One of the most outstanding features of the distribution of mineral deposits in eastern China is its heterogeneity.In fact, most of the gold deposits are concentrated in the northeastern part of China. Tectonically, this area strides across the northern part of the Sino-Korean Paraplatform in the south and the Jilin-Heilongjiang Fold Region in the north. The crustal composition in the area is characterized by high Au contents. For example, on the platform the average contents of Au in Archaean rocks range from 0.021 to 0.28 g/T. Therefore, gold deposits of the Jiapigou type and the Gaoxing type were formed. The former occurs in Precambrian basic volcanics and the latter in Precambrian migmatitic granites. In the Lower Proterozoic Au-and U-bearing conglomerates are developed in some places.Whether Hercynian magmatism is responsible for the formation of gold deposits or not is a question under discussion. Some deposits, though being considered as the Mesozoic, are emplaced within Hercynian granites. Besides, gold placers are widespread throughout the region. And in the upper reaches of the rivers where gold placers occur, Hercynian granites are often encountered. Thus it is possible that Hercynian magmatism may have contributed to the mineralization of Au.Extensive Mesozoic magmatism has once again brought a large amount fo gold to the upper crust of the region. Andesite, rhyolite, granite, granitic porphyry and quartz porphyry of this time all have high Au contents. Volcanic Au deposits of the Wufeng and Ciweigou types related to Jurassic an-desites and those of the Xiangluwanzi and Daomuhe types related to Jurassic rhyolites were formed during the period. Besides, in Heilongjiang, the Tuanjiegou deposit is related to granitic intrusion. At last, gold deposits are found in sediments of the Cretaceous, especially of the Quaternary.The rather low δ34S values (from+ 5.0 to+ 6.7 per mil for the Jiapigou type and from-1.3 to+ 5.0 per mil for the Ciweigou type) and a rather low 87Sr/86Sr initial ratio (0.7048 for the Ciweigou type) suggest a deep source possibility of Au.In North China, iron deposits are widely distributed throughout the region from Liaoning in the north to Jiangsu and Anhui in the south. Tectonically the area coincides with the Sino-Korean and Yangtze paraplatforms. The oldest iron deposits are of the Anshan type related to Achaean basic volcanism and concentrated chiefly in Liaoning and Hebei. At the beginning of the Sinian transgression, sedimentary iron ores were deposited in the Xuan-hua and Longguan basin. Even during the Devonian and Carboniferous, iron ores are extensively developed in Hubei and Hunan. The Mesozoic is another important period of the formation of iron deposits. Handan-Xingtai, Nanjing-Wufu and Daye are three main districts. The Handan-Xingtai type is associated with Mesozoic diorite and monzonite, the Nanjing-Wufu type with continental endesites and the Daye type with granitoids. Very low 87Sr/86Sr initial ratios of granitoids in the Daye districts imply a deep source possibility, whereas sulphur isotopes suggest a crustal contamination.Most of the copper deposits in eastern China are located in the Lower Yangtze River Valley. Tectonically the area belongs to the Yangtze Paraplat- form. The earliest mineralizations of Cu are found in the submarine volcano-sedimentary formation and metamorphic rocks. After the deposition of Cu during the Sinian, Cambrian and Ordovician, Cu mineralization reached its acme in the Mesozoic. The deposits of this time include the porphyry type, the skarn type, the volcanic type as well as that occurring in Cretaceous sandstones. The composition of associated intrusions varies from diorite up to granite. Some of the deposits have δS34 values of -4.0-+3.1 per mil, others from 3 to 8 per mil with mean value of 5 per mil and the author believes that Cu may have come from the depth. The fact that Cu contents of Paleozoic sedimentary rocks are all lower than Clark supports this assumption. |
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