Contact Zone Structure And Mineralization Significance Of Lingxiang Iron Deposit In Daye, Hubei Province

Lingxiang iron deposit, located in Daye, Hubei province, is a typical skarn type ore deposit, and a nearly exhausted mine. Ore bodies are mainly controlled by contact zone structure. Guided by the theories of essentials of metallogeny,structural geology in ore field,mineral exploration is, based on previously published data, the author carried on field investigation and studies in the laboratory. This study focuses on the relationship between the structure, especially, the contact zone structure, and the mineralization.Regionally, Lingxiang iron deposit lies in the triangle area of southeast Hubei province, controlled by the northwest Xiangfan-Guangji fault,the north-north-east Tuanfeng-Wenquan fault,the transmeridional Changyang-Yangxin fault. The triangle ore concentration area is the transition zone of Yangtze plate and North China Craton. In the Indosinian period, the EW direction folds formed by the north-south compression, previous to the mineralization, laid the foundation for the ore controlling structure; in the Yanshanian period, the north-north-east direct structure fromed, which, together with the Indosinian structure, is one of the most important factors controlling thetion of the skarn and the iron ore bodies. The ore deposits in this diggings are distributed with the shape of grid, which is a direct result of the distribution of the structures. From the west to the east, the diggings could be divided to three ore belts:the west ore belt, and the middle ore belt, the east ore belt.According to the complexity of the contact zone, the contact zone is divided into simple contact zone,complex contact zone,transitional contact zone. The complexity of the contact zone mainly includes the complexity of structure and the assemblage of rock and stratum. Simple contact zone mostly distributes in southern margin of the ore district. Complex contact zone mostly distributes in Naojiao ore block,Guangshan ore block. Transitional contact zone mainly distributes in Shizishanbei ore block,Xiaobaoshan ore block,Liujiafan ore block,Tiezishan ore block. I select Liujiafan contact zone,Tiezishan contact zone,Guangshan contact zone,Shizishanbei contact zone as the main object of this study, Guangshan ore body,Xiaobaoshan ore body,Liujiafan ore body,Shizishanbei ore body as the typical ore bodies. The research shows that simple contact zone is not favorable for mineralization. The marble is out of broken and the shape of contact zone of diorite and carbonate is simple in the southern contact zone, for the construction activity is weak, so this kind of contact zone is not conducive for ore-forming fluid to aggregate and not conducive for the evolution of the ore-forming reactions. In contrast, the complex contact zone is the intersection of folds and faults where the Triassic carbonate rocks get consumingly fragmentated, and the contact area of diorite and carbonate rocks increases. Thus, it is propitious for the ore-forming fliud to aggregate and the mineral to be precipitated, and thick skarn rock,iron ore deposit forms.In this study, GeoMine3D software is used to establish the 3D visualization model of the contact zone and ore bodies. The results show that the contact zone structure of Guangshan ore block is complex. The marble resides between diorite and ore bodies, especially in the middle part and the bottom of ore bodies. Generally there is a small quantity of marble left, and in some sections, there is no marble left, only skarn and ore deposit left. The ore bodies lie in the intersection part of fault and anticline, and are enwrapped by diorite. The diorite locates in the underside of marble, and Cretaceous strata located on the top of marble. The contact zone of Shizishanbei ore block is transitional contact zone. Its complexity is between simple contact zone and complex contact zone. In Shizishanbei ore block, the the contact area of diorite and carbonate rocks is comparatively large, so it is favorable for metasomatism. However, compared with Guangshan ore block, the marble is not completely broken in Shizishanbei ore block, for the construction activity is weaker, and more marble resides. The ore bodies mainly distributes around the edge of the contact zone, and the size of the ore bodies is comparatively small. The contact zone structure of Liujiafan ore block is comparatively complicated. The exterior of Liujiafan contact zone is uneven. The convex part of contact zone is not favorable of mineralization, and the concave part of contact zone where the inclination of contact zone changes from gradient to less gradient, is more favorable of mineralization. The shape and attitude of iron ore are consistent with the contact zone structure, and the distribution of ore bodied have close correlation with the contact zone.The more complex the contact zone structure is, the greater significance it is. The complexity of the shape of contact zone is mainly related to the complexity of folds and faults. The complex contact zone is usually formed as the result of the composite structure of folds and faults. In addition, the lithology of stratum and the assemblage of rock and stratum is an important factor affecting the structural complexity of the contact zone. As the influence of the tectonic stress, the carbonate rocks and clastic rocks have discrepancy in deformation at the conterminous position, because the mechanical properties, the mineral composition and chemical properties of clastic rocks and carbonate rocks are different.In the northern margin of the ore district, Lingxiang diorite contacts with Cretaceous strata directly. Triassic Daye group carbonate rocks and Puqi group shale exist occasionally. These supply the condition of magmatic rock and strata for the mineralization. The northern margin of the contact zone is rebuilt by faults and folds to a certian extent. The contact zone of Guangshan and Naojiao ore block is a kind of complex contact zone, combined by the trap-contact zone structure,fold-contact zone structure,fault-contact zone structure. And the marble is fragmented, so the residual marble may exist in the deep part of the anticline, where is profitable for prospecting. Combined with the geological,geophysical and drilling datas, the essay draw the conclusion that there is a good prospecting in the deep part of the area between Guangshan and Naojiao ore block.