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微裂隙对于岩石的物理性质有重要影响.通过光学显微镜对显微裂隙进行的观察,难以将薄片的制作过程中产生的裂隙同自然裂隙区分;其次,观测的裂隙大小限制在0.1mm或以上数量级,一些重要细节观察不到.扫描电镜的高放大倍数和三维分辨率使其成为适合于裂隙研究的理想工具.利用扫描电镜观测了浙江花岗岩在室温下由51.6MPa压力产生的裂隙的发育过程.观察花岗岩的表面以研究其微裂隙和矿物的解理、晶形及破裂作用.微裂隙分为3种类型:晶体内裂隙(完全发育在颗粒内部),晶体间裂隙(穿过颗粒边界进入其他颗粒中),颗粒边界裂隙(沿颗粒边界发育或与边界重合).本研究中的花岗岩为中—粗粒(1～6mm),经过蚀变,约含40%斜长石,25%钾长石,25%石英,10%镁铁矿物(主要为黑云母和白云母).(1)石英裂隙表面的石英颗粒具有边界破裂和贯穿颗粒破裂.贯穿石英颗粒的破裂常呈贝壳状断口.变形集中带与滑动面相伴,其上发育有擦痕和沟槽,这是石英典型的脆性破裂类型.石英矿物的贝壳状破裂产状指示其变形作用早期的碎裂作用,在变形作用中发生交代作用.一些平滑的破裂面上没有石英颗粒的微裂隙构造,但在石英表面却有明显的擦痕面,可指示应力的方向.由于石英的各向异性,这些面也是由贯穿颗粒破裂所形成.一些开放的裂隙集中于石英晶体之中或沿
The microcracks have an important influence on the physical properties of the rock.It is difficult to distinguish the fractures produced during the fabrication of the sheet from the natural fractures by observing the microcracks with an optical microscope.Secondly, the observed fracture size is limited to the order of 0.1 mm or more , And some important details can not be observed.The high magnification and three-dimensional resolution of SEM make it an ideal tool for fracture research.The growth of fractures produced by pressure of 51.6MPa in Zhejiang granite at room temperature was observed by scanning electron microscope. The surface of the granite is observed to study its microcracks and the cleavage, crystal form and fracture of the minerals.The microcracks are divided into three types: intragranular fissures (fully developed within the grain), intergranular fissures (crossing the grain boundaries into other grains ), Grain boundary fissures (developed along the grain boundaries or coinciding with the boundaries). The granites in this study are medium-coarse grains (1 ~ 6mm), after alteration, contain about 40% plagioclase and 25% potassium feldspar , 25% quartz and 10% mafic minerals (mainly biotite and muscovite). (1) Quartz grains on the surface of quartz crack have boundary rupture and rupture throughout the grain. Shell-shaped fracture. Deformation concentrated zone along with the sliding surface, there are scratches and grooves developed on it, which is a typical type of brittle fracture of quartz. The shell-like rupture of quartz minerals indicates the role of its role in the early crushing deformation in the Metamorphism occurred during the exchange of some smooth rupture surface without quartz grain micro-fissure structure, but the quartz surface has a significant scratch surface, indicating the direction of stress due to quartz anisotropy, these surfaces are also caused by Formed through the rupture of particles Some open fractures are concentrated in or along quartz crystals