蘇北連云港地區(qū)韌性剪切帶顯微構(gòu)造特征及變形溫度限制
發(fā)布時(shí)間：2018-08-01 14:08
【摘要】：連云港地區(qū)位于變質(zhì)帶西段南部,屬于揚(yáng)子板塊向華北板塊俯沖而形成的大別-蘇魯高壓-超高壓變質(zhì)帶的重要組成部分。變質(zhì)帶北界以五蓮煙臺(tái)斷裂與華北板塊為鄰,南界沿嘉山響水?dāng)嗔褨|段與揚(yáng)子板塊相連,西界以郯廬斷裂與北中國板塊相隔。蘇魯高壓-超高壓變質(zhì)帶在折返后期遭受剪切作用改造,形成連云港地區(qū)NE-SW走向的韌性剪切帶。本文結(jié)合野外宏觀變形現(xiàn)象、顯微構(gòu)造分析以及糜棱巖中石英結(jié)晶學(xué)優(yōu)選方位的EBSD測(cè)量,對(duì)早晚兩期糜棱巖化進(jìn)行多方面對(duì)比。同時(shí)對(duì)于剪切帶兩期變形表現(xiàn)及變形溫度限定,結(jié)合區(qū)域變質(zhì)階段劃分判斷變形壓力,進(jìn)而闡述了連云港地區(qū)早白堊世構(gòu)造格局與演化。連云港地區(qū)韌性剪切帶構(gòu)成的宏觀構(gòu)造輪廓在幾何形態(tài)上呈穹窿狀,以石梁河水庫為界,其北西處面理產(chǎn)狀傾向NW,線理傾伏向NWW,野外不對(duì)稱層間褶皺指示上盤向北西下滑;其南東處面理產(chǎn)狀傾向SE,線理傾伏向SE,野外不對(duì)稱透鏡體及長石殘斑指示上盤向北西逆沖。剪切帶內(nèi)記錄了兩期變形:早期的高溫剪切(D1)伴隨著退變質(zhì)角閃巖相礦物組合,長石呈現(xiàn)出柱狀拉長,石英的動(dòng)態(tài)重結(jié)晶以顆粒邊界遷移為主,巖石整體呈韌性變形;晚期的低溫剪切(D2)伴隨著退變質(zhì)綠片巖化,長石呈現(xiàn)剛性破裂的脆性變形,石英的動(dòng)態(tài)重結(jié)晶以亞顆粒旋轉(zhuǎn)和膨凸重結(jié)晶為主,巖石整體呈脆韌性-脆性變形。穹窿從核部到翼部,變形變質(zhì)表現(xiàn)逐步減弱,由高溫變形/角閃巖相過渡到低溫變形/綠片巖相。對(duì)角閃巖相中的被早期剪切變形所改造的黑云母和綠片巖相中伴隨晚期變形新生的白云母使用云母鈦溫度計(jì),并結(jié)合區(qū)域變質(zhì)壓力分析結(jié)果為:D1期溫壓條件可限定為t1=505~523℃,p1=0.50~0.70 GPa。D2期變形溫壓條件上限為:t2=448~493℃,p2=0.30~0.35 GPa。通過與五蓮地區(qū)剪切帶區(qū)域上對(duì)比從角閃巖相過渡到綠片巖相的剪切帶構(gòu)造特征以及變形特征,認(rèn)為這兩期期變形與區(qū)域中生代伸展構(gòu)造相關(guān),變形時(shí)間可能為晚中生代,認(rèn)為剝露抬升過程與五蓮地區(qū)抬升階段一致,并建立了連云港地區(qū)高壓-超高壓變質(zhì)帶早白堊世剝露演化模式。
[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，
本文編號(hào)：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，
本文編號(hào)：2157824
本文鏈接：http://sikaile.net/kejilunwen/diqiudizhi/2157824.html
最近更新
教材專著
