【摘要】 甘肃白银厂小铁山变形变质熔结-沉积火山岩区石英角班凝灰岩系列的岩石中,石英碎斑形态组构(椭球体)的XY面平行于第一期劈理面,X轴与劈理面上的火山砾和矿物拉长线理平行或近于平行。石英碎斑具有脆性变形特征(微裂纹),也具有韧性变形特征(波状消光、变形纹、亚晶和新晶)。石英碎斑光轴极密不明显,新晶光轴为均匀组构。在变形较强烈的地区,形成这种组构的主要原因是岩石中基质(凝灰质)的存在。更多还原

【Abstract】 The shape and c-axis fabrics of the quartz-porphyroclasts in the qua-rtz-keratophyre-series formed in palaeozoic age and deformed and meta-morphosed during Caledonian Cycle under chlorite-facies in Xiaotieshan,Baiyin Open-pit Mine, Gansu Province, has been studied. The preferred orientation of Z-axis of shape fabric shown by the quar-tz-porphyroclasts (in 19 specimens) and the preferred orientation of thepoles of cleavages in the rock with 140 measurements are well coincident.The preferred orientation of X-axis in the shape fabric is nearly parallelor subparallel to that of the lineation which is expressed by the parallelaligment of the stretched volcanic breccias and minerals on the cleavage. The characteristics of ductile deformation (undulatory extinction, de-formation lamellae, subgrain and new grain) as well as that of brittledeformation (microfracture) have been found under microscope in thequartz-porphyroclasts, it is demonstrated that the quartz-porphyroclastshad been deformed in a brittle-ductile transition manner, although itsmatrix (tuffaceous) had been deformed in a ductile process. In such astrongly deformed area (X/Z 5.0, determined from strain analysis ofthe volcanic breccias), the degree of preferred orietations represented byboth the c-axis and shape fabrics of the quarfz-porphyroclasts is excep-tionally low, and it is believed that the formations of these two fabricsare probably controlled by the relatively high proportion in content ofthe matrix material.更多还原