岩石变形、流体压力与热液成矿关系的研究现状

Deformation of rock,fluid pressures and hydrothermal deposits

地壳中岩石的变形模式受构造应力、流体压力和上覆岩层重力共同作用的影响。岩石组成和构造应力的大小、方向决定着岩石的变形过程,同时岩石的破裂还受先存断裂构造的影响。流体压力增大,岩石可以发生水力破裂,而引起水力引张破裂的条件是σ1-σ3〈4T和Pf=σ3＋T。随着深度的增加,受地温梯度的影响,岩石由脆性变形向韧性变形转变。在无流体超压影响的情况下,脆韧性转换的温度在300~450℃之间,大约在地壳15km处。当流体压力和应变速率增大时,韧性条件下的岩石变形行为由韧性向脆性变化,脆韧性转变的深度随之增大。从构造角度探讨热液成矿作用,热液矿床形成的深度与流体压力、应变速率、裂隙的发育、介质的渗透率、温度变化等相关。岩石断裂的类型和方向影响岩石的渗透率,提供流体运移的通道和聚集场所,控制矿床形成的深度、位置和矿体产状。

Deformation pattern of rocks in earth＇s crust is effected by tectonic stress,fluid pressure and gravity of the overlying strata.And the composition of rock and the size and the direction of tectonic stress determine the deformation of rock,while its breakdown is controlled by the pre-existed fault.The hydraulic fracture of rock occurs when the fluid pressure increases,however,the conditions of hydraulic extension fracture are σ1-σ34T and Pf=σ3＋T.With the increase of depth in earth,the deformation of rocks changes from brittle behavior to ductile behavior by the influence of geothermal gradient.As long as there is no effection of fluid overpressure,brittle-ductile transition of rock happens in about 15km in the crust,on the condition of 300~450 ℃.When the fluid pressure and the strain rate increase,the deformation of rock will change from ductile to brittle in the ductile region and the depth of brittle-ductile transition will increase.On the perspective of tectonic mineralization,the depth of the hydrothermal deposits formation are related to the fluid pressure,strain rate,fracture and fault,the permeability of medium and the temperature.The migration and gathering place of fluid,the depth of the ore-forming,position and the orientation of orebodies and the permeability of rock are all affected by the types and direction of rock fracture.