苏北连云港地区韧性剪切带显微构造特征及变形温度限制
发布时间：2018-08-01 14:08
【摘要】：连云港地区位于变质带西段南部,属于扬子板块向华北板块俯冲而形成的大别-苏鲁高压-超高压变质带的重要组成部分。变质带北界以五莲烟台断裂与华北板块为邻,南界沿嘉山响水断裂东段与扬子板块相连,西界以郯庐断裂与北中国板块相隔。苏鲁高压-超高压变质带在折返后期遭受剪切作用改造,形成连云港地区NE-SW走向的韧性剪切带。本文结合野外宏观变形现象、显微构造分析以及糜棱岩中石英结晶学优选方位的EBSD测量,对早晚两期糜棱岩化进行多方面对比。同时对于剪切带两期变形表现及变形温度限定,结合区域变质阶段划分判断变形压力,进而阐述了连云港地区早白垩世构造格局与演化。连云港地区韧性剪切带构成的宏观构造轮廓在几何形态上呈穹窿状,以石梁河水库为界,其北西处面理产状倾向NW,线理倾伏向NWW,野外不对称层间褶皱指示上盘向北西下滑;其南东处面理产状倾向SE,线理倾伏向SE,野外不对称透镜体及长石残斑指示上盘向北西逆冲。剪切带内记录了两期变形:早期的高温剪切(D1)伴随着退变质角闪岩相矿物组合,长石呈现出柱状拉长,石英的动态重结晶以颗粒边界迁移为主,岩石整体呈韧性变形;晚期的低温剪切(D2)伴随着退变质绿片岩化,长石呈现刚性破裂的脆性变形,石英的动态重结晶以亚颗粒旋转和膨凸重结晶为主,岩石整体呈脆韧性-脆性变形。穹窿从核部到翼部,变形变质表现逐步减弱,由高温变形/角闪岩相过渡到低温变形/绿片岩相。对角闪岩相中的被早期剪切变形所改造的黑云母和绿片岩相中伴随晚期变形新生的白云母使用云母钛温度计,并结合区域变质压力分析结果为:D1期温压条件可限定为t1=505~523℃,p1=0.50~0.70 GPa。D2期变形温压条件上限为:t2=448~493℃,p2=0.30~0.35 GPa。通过与五莲地区剪切带区域上对比从角闪岩相过渡到绿片岩相的剪切带构造特征以及变形特征,认为这两期期变形与区域中生代伸展构造相关,变形时间可能为晚中生代,认为剥露抬升过程与五莲地区抬升阶段一致,并建立了连云港地区高压-超高压变质带早白垩世剥露演化模式。
[Abstract]:Lianyungang area is located in the south of the western segment of the metamorphic belt, which is an important part of the Dabie Sulu high pressure metamorphic belt formed by the Yangtze plate subducting to the North China plate. The northern boundary of the metamorphic belt is adjacent to the North China plate, the southern boundary is connected with the Yangtze plate along the eastern segment of the Xiangshui fault of Jiashan, and the western boundary is separated by the Tanlu fault and the North China plate. The Sulu HP-UHP metamorphic belt was shearing in the late exhumation period and formed the ductile shear zone of NE-SW strike in Lianyungang area. Combined with field macroscopic deformation, microstructural analysis and EBSD measurement of quartz crystallographic preferred azimuth in mylonite, this paper compares mylonitization in two phases in the morning and evening. At the same time, the deformation pressure is judged according to the regional metamorphic stage, and the early Cretaceous tectonic pattern and evolution in Lianyungang area are expounded. The macrostructure of the ductile shear zone in Lianyungang area is in the shape of a dome in geometry. The boundary of the reservoir is Shilianghe reservoir. The northwestern side of the structure tends to NW, the line tilts to NWW.The field asymmetric interlaminar fold indicates that the upper disc is sliding northwestward. In the south and east, the occurrence of surface texture is inclined toward SE, the linear tendency is inclined toward SE, and the field asymmetric lens and feldspar remnant indicate that the upper disc is thrusting northwestward. Two stages of deformation were recorded in the shear zone: the early high temperature shear (D1) was accompanied by retrograde amphibolite facies mineral assemblage, feldspar showed columnar elongation, the dynamic recrystallization of quartz was dominated by grain boundary migration, and the whole rock showed ductile deformation; In the late stage of low temperature shearing (D2) accompanied by retrograde metamorphic greenschist, feldspar presents brittle deformation of rigid fracture, dynamic recrystallization of quartz is dominated by subparticle rotation and bulging recrystallization, and the whole rock is brittle ductile brittle deformation. The deformation and metamorphism of the dome decreases gradually from the nucleus to the wing, from high temperature deformation / amphibolite facies to low temperature deformation / greenschist facies. Mica titanium thermometers are used for biotite modified by early shear deformation in amphibolite facies and Muscovite associated with late deformation in greenschist facies. Combined with the regional metamorphic pressure analysis, the temperature and pressure conditions at 1: D1 stage can be limited to t _ 1 ~ (50) 523 鈩，
本文编号：2157824
[Abstract]:Lianyungang area is located in the south of the western segment of the metamorphic belt, which is an important part of the Dabie Sulu high pressure metamorphic belt formed by the Yangtze plate subducting to the North China plate. The northern boundary of the metamorphic belt is adjacent to the North China plate, the southern boundary is connected with the Yangtze plate along the eastern segment of the Xiangshui fault of Jiashan, and the western boundary is separated by the Tanlu fault and the North China plate. The Sulu HP-UHP metamorphic belt was shearing in the late exhumation period and formed the ductile shear zone of NE-SW strike in Lianyungang area. Combined with field macroscopic deformation, microstructural analysis and EBSD measurement of quartz crystallographic preferred azimuth in mylonite, this paper compares mylonitization in two phases in the morning and evening. At the same time, the deformation pressure is judged according to the regional metamorphic stage, and the early Cretaceous tectonic pattern and evolution in Lianyungang area are expounded. The macrostructure of the ductile shear zone in Lianyungang area is in the shape of a dome in geometry. The boundary of the reservoir is Shilianghe reservoir. The northwestern side of the structure tends to NW, the line tilts to NWW.The field asymmetric interlaminar fold indicates that the upper disc is sliding northwestward. In the south and east, the occurrence of surface texture is inclined toward SE, the linear tendency is inclined toward SE, and the field asymmetric lens and feldspar remnant indicate that the upper disc is thrusting northwestward. Two stages of deformation were recorded in the shear zone: the early high temperature shear (D1) was accompanied by retrograde amphibolite facies mineral assemblage, feldspar showed columnar elongation, the dynamic recrystallization of quartz was dominated by grain boundary migration, and the whole rock showed ductile deformation; In the late stage of low temperature shearing (D2) accompanied by retrograde metamorphic greenschist, feldspar presents brittle deformation of rigid fracture, dynamic recrystallization of quartz is dominated by subparticle rotation and bulging recrystallization, and the whole rock is brittle ductile brittle deformation. The deformation and metamorphism of the dome decreases gradually from the nucleus to the wing, from high temperature deformation / amphibolite facies to low temperature deformation / greenschist facies. Mica titanium thermometers are used for biotite modified by early shear deformation in amphibolite facies and Muscovite associated with late deformation in greenschist facies. Combined with the regional metamorphic pressure analysis, the temperature and pressure conditions at 1: D1 stage can be limited to t _ 1 ~ (50) 523 鈩，
本文编号：2157824
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