摘要
证明璜茅-五城-屯溪韧性剪切带的存在能证实前人的推断和认识,为区域构造研究特别是皖浙赣断裂的研究提供研究资料,也能为区域内金矿找矿提供新的找矿方向。针对皖南天井山地区璜茅-五城-屯溪韧性剪切带进行的剖面地质研究,结果显示,璜茅-五城-屯溪韧性剪切带为大型韧性剪切带,在研究区内总体呈喇叭状展布,宽约2km^5km,向NE发散,向SW收敛。并在元古代中形成了大型的A型褶皱。宏观上强弱分带明显,以元古代地层和晋宁期岩体的接触带为最强应变带,发育超糜棱岩,应变强度向两侧逐渐减弱,在弱应变带发育糜棱岩化千枚岩和初糜岩。微观上,韧性变形显微构造发育较好,以发育旋转碎斑、压力影和石英的膨突动态重结晶为主,其韧性变形机制为中低温条件下的位错滑移、碎裂流动以及扩散物质迁移。EBSD对韧性剪切带的石英组构分析显示,石英以菱面{10-11}<a>和底面{0001}<a>滑移为主,变形温度为中低温(400℃~550℃)及低温(<400℃)。宏微观运动学特征和石英组构特征显示韧性剪切带至少经历了两次活动。塑性变形机制和EBSD石英组构显示韧性剪切带变质相为低绿片岩相-高绿片岩相,局部可达低-中角闪岩相。
The characteristics of the Huangmao-Wucheng-Tunxi ductile shear zone in the Tianjingshan area,south of Anhui Province are studied on the basis of the geological section survey. It reveals that it is a large scale ductile shear zone with a trumpet in shape. It diverges to the northeast with a width of 2 km-5 km and converges in the southwest. Large scale ＂A＂ type fold occurs in the Proterozoic rocks and the contact zone of Proterozoic strata and the Jinning tectonic stage rock mass is the most strong strain belt where ultramylonite is well developed. The strain strength is gradually weakened from the center of shear zone to both shear zone boundary and mylonitized phyllite and protomylonite mainly develope in the weak strain zone. Rotating porphyroclasts,pressure shadow, and bulging recrystallized grains are the most common microstructures. Ductile deformation mechanism is dislocation glide, cataclastic flow and diffusive mass transfer in the middle and low temperature conditions. EBSD fabric analysis shows that quartz grains in mylonite are mainly deformed along their rhombohedral glide system and basal glide system in a low-middle temperature of 400℃-550℃ and a low temperature of 〈400 ℃. It also shows that the ductile shear zone has experienced at least two stage deformation activities. The ductile deformation mechanism and quartz EBSD fabric analysis indicate that the metamorphic facies of ductile shear zone is low-greenschist to high-greenschist facies,and in some areas even rea- ches low-middle amphibolite facies.
出处
《矿物岩石》
CAS
CSCD
北大核心
2016年第1期96-105,共10页
Mineralogy and Petrology
基金
安徽省国土资源科技项目"皖南地区大型韧性剪切带与金成矿作用研究"(编号:2013-K-02)
关键词
天井山
大型韧性剪切带
EBSD
石英组构
皖南
Tianjingshan
large scale ductile shear zone
EBSD
quartz fabrics
Southern Anhui
