Minimum critical thickness of dike for ore-bearing fluid injection: A new approach applied to the Shihu gold deposit, Hebei Province, North China
| Autor: | Zong-Feng Yang, Cui Liu, Yuwang Wang, Dedong Li, Jiu-Long Zhou, Zhaohua Luo, Jingbin Wang |
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| Rok vydání: | 2012 |
| Předmět: |
Critical thickness
Dike geography Bearing (mechanical) geography.geographical_feature_category lcsh:QE1-996.5 Minor intrusion Geochemistry Earth and Planetary Sciences(all) Dike swarm Numerical simulation Cooling time law.invention Diorite lcsh:Geology Viscosity law Magma General Earth and Planetary Sciences Transmagmatic fluid Quartz Geology |
| Zdroj: | Geoscience Frontiers, Vol 3, Iss 5, Pp 717-728 (2012) |
| ISSN: | 1674-9871 |
| DOI: | 10.1016/j.gsf.2012.02.001 |
| Popis: | According to the metallogenic theory by transmagmatic fluid (TMF), one magmatic intrusion is a channel of ore-bearing fluids, but not their source. Therefore, it is possible to use TMF’s ability for injection into and for escaping from the magmatic intrusion to evaluate its ore-forming potential. As the ore-bearing fluids cannot effectively inject into the magmatic intrusion when the magma fully crystallized, the cooling time and rates viscosity varied can be used to estimate the minimum critical thickness of the intrusion. One dimensional heat transfer model is used to determine the cooling time for three representative dikes of different composition (granite porphyry, quartz diorite and diabase) in the Shihu gold deposit. It also estimated the rates viscosity varied in these time interval. We took the thickness of dike at the intersection of the cooling time – thickness curve and the rates viscosity varied versus thickness curve as the minimum critical thickness. For the ore-bearing fluids effectively injecting into the magma, the minimum critical thicknesses for the three representative dikes are 33.45 m for granite porphyry, 8.22 m for quartz diorite and 1.02 m for diabase, indicating that ore-bearing dikes must be thicker than each value. These results are consistent with the occurrence of ore bodies, and thus they could be applied in practice. Based on the statistical relationship between the length and the width of dikes, these critical thicknesses are used to compute critical areas: 0.0003–0.0016 km 2 for diabase, 0.014–0.068 km 2 for quartz diorite and 0.011–0.034 km 2 for granite porphyry. This implies that ore-bearing minor intrusions have varied areas corresponding to their composition. The numerical simulation has provided the theoretical threshold of exposed thickness and area of the ore-bearing intrusion. These values can be used to determine the ore-forming potentials of dikes. |
| Databáze: | OpenAIRE |
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