BACKGROUNDThe altered wall rocks of copper deposits and associated ore bodies have a close genetic and spatial relationship. By analyzing the alteration characteristics of copper deposits, the physical and chemical conditions of the mineralization, the migration, enrichment and evolution of ore-forming elements in the hydrothermal fluid can be obtained. The alteration features ultimately indicate the mineralization degree of the copper deposit and the location of the ore body. The hyperspectral core scanning system is a new type of technical testing method, developed in recent years. This article documents the first time of studying the representative cores from the Chengmenshan Tielukan copper deposit by the hyperspectral core scanning system. At the same time, altered minerals were analyzed by electron probe microanalysis (EMPA). Thus, further revealing the metallogenic mechanism of the Chengmenshan copper deposit.

OBJECTIVESTo investigate the alteration features of the Chengmenshan Tielukan copper deposit and to understand the ore genesis.

METHODSSamples were analyzed by a hyperspectral core scanning system and electron probe microanalyzer.

RESULTSThe results showed that in the typical borehole ZKJ9-7, the typical spectral curves of montmorillonite and carbonate were dominated at 0-350m, whereas the typical spectral curves of kaolin and muscovite were dominated at 350-578m. The mineral composition variation from the surface to the depth of the Tielukan region in the Chengmenshan copper deposit periphery was montmorillonite+kaolinite →carbonate+montmorillonite →carbonate →muscovite+kaolinite+montmorillonite →muscovite+kaolinite+chlorite.

CONCLUSIONSIn the Tielukan region, the contact zone between the granodiorite porphyry and the carbonate wall rocks controls the superficial part, but in the deep part it has alteration processes such as skarnization, silicification and chloritization. These alteration processes will conduce to the formation and enrichment of the copper mine. The deep part of the drilling core also shows that rock component exchange occurred on both sides of the contact zone, resulting in the formation of the skarn in the deep part. When the ascending mineralized solution flows along the carbonate interface, CaO in carbonate diffuse to the ferrosilicon rock and aluminosilicon rock along with the intergranular solution. In contrast, FeO, Al₂O₃ and SiO₂ in the ferrosilicon rock and aluminosilicon rock diffuse to limestone, and thus rock components exchange on both sides of the contact zone generating the skarn in the deep part. The formation of copper-rich skarn deposit is closely related to the components exchange between solution and rock. The diffusion effect caused by the concentration difference of the components plays an important role.