| 湘赣粤环形构造的影象分析其找矿应用意义探讨 |
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| 引用本文：.1985.Image feature of hunan-jiangxi-guangdong circular structure and its application effects in mineral exploration[J].Mineral Deposits,4(3):40~50,18 |
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| Image feature of hunan-jiangxi-guangdong circular structure and its application effects in mineral exploration |
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| Abstract:The Hunan-Jiangxi-Guangdong(Xiang-Gan-Yue)circular structure(here inafter called XGY circular structure for short)is located in the middle part of the NanMing compressive structure zone. The geological structures of this region are complicated, and linear structures of different directions are well developed. Magmatic activities occurred repeatedly, and magma intruded for several times in different periods. Especially during Indosinian-Yenshanian periods, a great abundance of granites were invaded. The strata from the Sinian to the Quaternary are preserved perfectly. There exist many metallic deposits in the area, especially tungstun and tin deposits. The present paper deals with the features of the geological structures in the area, the relationship between the Nanling compressive structure zone and the granite, and effects of applying circular structure in mineral exploration. All this lies on the basis of various geological data in this region obtained by using multispectral band images at different scales, remote sensing technology of computer processing in some important districts, combinatorial analysis of the structure, sedimentation, metamorphism, magmatic activities, and correlative analysis of the image information. The author has obtained in the important district a lot of information of small-middle circular structures and bline magmatic rocks from various images acquired by means of different templets, the ratio associations of different bands, and the selection and classification of typical associations of different bands, and the selection and classification of typical target districts. The paper provides areas for ore prospecting and for detecting blind deposits around small-middle circular structures. The present paper indicates that there exists a massive magma chamber lying under the XGY circular structure, and the XGY circular structure itself is the roof shape of the massive magma chamber at the surface. There were at least two periodic magma activities in the magma chamber. The first one occurred during Early Paleozoic when the elevation and subsidence movements dominated in the Wanan-Shueichuan fault; the magma intruded along the SN structure. The second one chiefly took place from Triassic to Cretaceous, and this magmatic intrusion spread extensively. The main part of the XGY circular structure has been unheaving since Mesozoic. The emergenice of many small Mesozoic intrusive masses suggests the intensification of the elevation and the subsidence. This diverse movement formed a set of Mesozoic basins around the main part of the XGY circular structure. The main part of the XGY circular structure still upheaved in Cenozoic, and the Cenozoic basins around this structure was superimposed on the Mesozoic basins. The difference of the spectrum features and the image patterns between the XGY circular structure and the geological bodies around it is very small, with the special circular patterns existing prominently in the Nanling Mountains. There are also other circular structures in South China belonging to this type. The XGY circular structure, however, is most typical whther from its images shape, its dimension, its spectrum features, or from its interpretation indicators, and it represents a sort of circular structures which were formed by the remelted granite batholiths in the Sialsphere of South China. After the image enhancement and information extraction, the author has detected and distinguished seven circular anomalous districts which are very similar in color and anomaly shape to the corresponding typical target districts in the main part of the XGY circular structure investigating the combinatorial relationship between circle and line, and the analysis of the logical correlation. On the basis of the experience gained by previous workers on processing the remote sensing data, in combination with the special geological and gee graphical conditions of this region, the author suggests that the colorful ratio image composed of the ratios with blue, green and red coding can suppress the interference of the plant noise and extract small-middle or small circular information as well as the light blue-green anomaly which is related to the mineralizations of tungstun and tin. |
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