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Structural geometry of orogenic gold deposits: Implications for exploration of world-class and giant deposits 被引量:22
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作者 David I.Groves M.Santosh +1 位作者 Richard J.Goldfarb Liang Zhang 《Geoscience Frontiers》 SCIE CAS CSCD 2018年第4期1163-1177,共15页
With very few exceptions, orogenic gold deposits formed in subduction-related tectonic settings in accretionary to collisional orogenic belts from Archean to Tertiary times. Their genesis, including metal and fluid so... With very few exceptions, orogenic gold deposits formed in subduction-related tectonic settings in accretionary to collisional orogenic belts from Archean to Tertiary times. Their genesis, including metal and fluid source, fluid pathways, depositional mechanisms, and timing relative to regional structural and metamorphic events, continues to be controversial. However, there is now general agreement that these deposits formed from metamorphic fluids, either from metamorphism of intra-basinal rock sequences or de-volatilization of a subducted sediment wedge, during a change from a compressional to transpressional, less commonly transtensional, stress regime, prior to orogenic collapse. In the case of Archean and Paleoproterozoic deposits, the formation of orogenic gold deposits was one of the last events prior to cratonization. The late timing of orogenic gold deposits within the structural evolution of the host orogen implies that any earlier structures may be mineralized and that the current structural geometry of the gold deposits is equivalent to that at the time of their formation provided that there has been no significant post-gold orogenic overprint. Within the host volcano-sedimentary sequences at the province scale, world-class orogenic gold deposits are most commonly located in second-order structures adjacent to crustal scale faults and shear zones, representing the first-order ore-forming fluid pathways, and whose deep lithospheric connection is marked by lamprophyre intrusions which, however, have no direct genetic association with gold deposition. More specifically, the gold deposits are located adjacent to ~10°-25° district-scale jogs in these crustal-scale faults. These jogs are commonly the site of arrays of ~70° cross faults that accommodate the bending of the more rigid components, for example volcanic rocks and intrusive sills, of the host belts. Rotation of blocks between these accommodation faults causes failure of more competent units and/or reactivation and dilation of pre-existing structures, leading to deposit-scale focussing of ore-fluid and gold deposition.Anticlinal or antiformal fold hinges, particularly those of 'locked-up' folds with ~30° apical angles and overturned back limbs, represent sites of brittle-ductile rock failure and provide one of the more robust parameters for location of orogenic gold deposits.In orogenic belts with abundant pre-gold granitic intrusions, particularly Precambrian granitegreenstone terranes, the boundaries between the rigid granitic bodies and more ductile greenstone sequences are commonly sites of heterogeneous stress and inhomogeneous strain. Thus, contacts between granitic intrusions and volcano-sedimentary sequences are common sites of ore-fluid infiltration and gold deposition. For orogenic gold deposits at deeper crustal levels, ore-forming fluids are commonly focused along strain gradients between more compressional zones where volcano-sedimentary sequences are thinned and relatively more extensional zones where they are thickened. World-class orogenic gold deposits are commonly located in the deformed volcano-sedimentary sequences in such strain gradients adjacent to triple-point junctions defined by the granitic intrusions, or along the zones of assembly of micro-blocks on a regional scale. These repetitive province to district-scale geometrical patterns of structures within the orogenic belts are clearly critical parameters in geology-based exploration targeting for orogenic gold deposits. 展开更多
关键词 Structural geometry Tectonic history Fluid pathways Orogenic gold deposits exploration criteria
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Exploration of Key Points in Evaluation Criteria of Chinese Medicine in the Treatment of Cancer 被引量:1
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作者 杨宇飞 廖娟 《Chinese Journal of Integrative Medicine》 SCIE CAS 2010年第1期3-5,共3页
Although tumor node metastasis (TNM) staging in WM has been accepted and used with no reserve in the criteria of CM diagnosis and treatment of cancer, some differences still exist between CM and WM in the evaluation... Although tumor node metastasis (TNM) staging in WM has been accepted and used with no reserve in the criteria of CM diagnosis and treatment of cancer, some differences still exist between CM and WM in the evaluation criterion. The reason for this focuses on evaluation criterion of effects on solid tumor made by the World Health Organization (WHO), which does not reflect some aspects such as survival time of tumor patients or improvement in quality of life (QOL). Therefore, forerunners in the CM field have been making efforts to try to find an evaluation criteria that would integrate CM and WM, and thus could be approved by CM and WM specialists. 展开更多
关键词 exploration of Key Points in Evaluation criteria of Chinese Medicine in the Treatment of Cancer
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