Resolving the Routine Presence of Kyanite,Andalusite and Sillimanite across a Region using Foliation Intersection/Inflection Axes Preserved in Porphyroblasts,Petrographic Observations and Thermobarometry     

Asghar ALI 《《地质学报》英文版》2012,86(5):1241-1250

Constraints from P-T pseudosections (MnNCKFMASH system), foliation intersection/inflection axes preserved in porphyroblasts (FIAs), mineral assemblages and textural relationships for rocks containing all three Al2SiO5 polymorphs indicate a kyanite→ andalusite→ sillimanite sequential formation at different times rather than stable coexistence at the Al2SiO5 triple point. All three Al2SiO5 polymorphs grew in the Chl, Bt, Ms, Grt, St, Pl and Crd bearing Ordovician Clayhole Schist in Balcooma, northeastern Australia separately along a looped P-T-t-D path that swaps from clockwise to anticlockwise in the tectono-metamorphic history of the region. Kyanite grew during crustal thickening in an Early Silurian Orogenic event followed by decompression/heating, andalusite and fibrolitic sillimanite growth during Early Devonian exhumation.  相似文献   

Seismic properties of the upper mantle beneath Lanzarote (Canary Islands): Model predictions based on texture measurements by EBSD   总被引：1，自引：0，他引：1  

Pierre Vonlanthen  Karsten Kunze  Luigi Burlini  Bernard Grobety 《Tectonophysics》2006,428(1-4):65-85

We present a petrophysical analysis of upper mantle xenoliths, collected in the Quaternary alkali basalt fields (Series III and IV) from the island of Lanzarote. The samples consist of eight harzburgite and four dunite nodules, 5 to 15 cm in size, and exhibit a typical protogranular to porphyroclastic texture. An anomalous foliation resulting from strong recovery processes is observed in half of the specimens. The lattice preferred orientations (LPO) of olivine, orthopyroxene and clinopyroxene were measured using electron backscatter diffraction (EBSD). In most samples, olivine exhibits LPOs intermediate between the typical single crystal texture and the [100] fiber texture. Occasionally, the [010] fiber texture was also observed. Simultaneous occurrence of both types of fiber textures suggests the existence of more than one deformation regime, probably dominated by a simple shear component under low strain rate and moderate to high temperature. Orthopyroxene and clinopyroxene display a weaker but significant texture. The LPO data were used to calculate the seismic properties of the xenoliths at PT conditions obtained from geothermobarometry, and were compared to field geophysical data reported from the literature. The velocity of P-waves (7.9 km/s) obtained for a direction corresponding to the existing seismic transect is in good agreement with the most recent geophysical interpretation. Our results are consistent with a roughly W–E oriented fastest P-wave propagation direction in the uppermost mantle beneath the Canary Islands, and with the lithosphere structure proposed by previous authors involving a crust–mantle boundary at around 18 km in depth, overlaid by intermediate material between 11 and 18 km.  相似文献   

西藏东部嘉玉桥变质杂岩中片理化岩组主期面理形成及构造意义     

王根厚  周详  曾庆高  普布次仁 《地质通报》1998,(2)

西藏东部嘉玉桥变质杂岩中片理化岩组剪切运动方向为ＳＥ１４０°—ＮＷ３２０°,应变测量求得富林参数Ｋ平均值为２１３,表明主期面理变形为单剪与收缩机制的复合产物。由石英位错密度估算其差应力值平均为１４９５ＭＰａ,白云母形成温度３８３℃。经４０Ａｒ３９Ａｒ法年龄测定,获得主期变形时间为（１６４７±１３３）Ｍａ（白云母）～（１６６２７±０９９）Ｍａ（角闪石）。因此,嘉玉桥片理化岩组主期变形与区域上班公湖—怒江缝合带的形成演化有着密切的关系。  相似文献   

Himalayan structure and metamorphism south of the Main Mantle Thrust, Lower Swat, Pakistan   总被引：2，自引：0，他引：2  

J. A. DIPIETRO  R. D. LAWRENCE 《Journal of Metamorphic Geology》1991,9(4):481-495

Abstract During the Eocene-Oligocene, the Indian plate collided with the Kohistan arc along the Main Mantle Thrust (MMT) zone. The structure of the Lower Swat rock sequence, on the Indian plate directly south of the MMT, is a dome with a basement of granitic gneiss and quartz-rich schist unconformably overlain by amphibolitic and calcareous schist. The earliest superposed small-scale folds (F1 & F2) represent a progressive F1/F2 deformation that is associated with a single set of WSW-vergent large-scale folds (termed F2). These folds are inferred to have developed during oblique, WSW-directed overthrusting of the MMT suture complex onto the Lower Swat rock sequence. Metamorphism began during F1/F2 as indicated by an S1 foliation that developed during biotite-grade metamorphism. S1 is preserved as a relict texture in porphyroblasts that grew during a subsequent interkinematic phase during garnet- and higher grade metamorphism. The dominant, regional foliation (S2) developed following the interkinematic phase. S2 is associated with transposition of S1 and rotation or dismemberment of porphyroblasts. Annealing recrystallization followed S2 and continued during F3 thereby destroying or masking possible pre-existing stretching fabrics. Superposed F3 folds are upright and open with N-S axial trends. They may correlate with early doming of the Lower Swat rock sequence and with strike-slip displacement in the northern part of the MMT zone, north of the Lower Swat area. F3 was followed by retrograde metamorphism and development of E-W-trending, S-vergent F4 folds. F4 may be associated with a final phase of southward directed thrusting and inactivity in the MMT zone. Correlation of published ⁴⁰Ar/³⁹Ar ages with the metamorphic fabrics suggests that F1/F2 and F3 occurred in the Eocene, and that F4 developed in the Oligocene. F4 is the earliest indication of southward verging structures on this part of the Indian plate.  相似文献   

猫岭金矿床成矿构造演化特征   总被引：8，自引：0，他引：8  

邱小平 《矿床地质》2004,23(2):198-205

猫岭金矿是在克拉通变质岩区保存较好的含砷(毒砂)浸染型金矿之一，金矿脉并非单纯的硫化物脉，而是含毒砂-磁黄铁矿-黄铁矿的硅化石英脉，S1面理与金矿脉为同一构造期产物，形成于辽河旋回第一幕构造的伸展滑脱阶段。金矿成矿时代为古元古代，绝对年龄为2000～2200Ma。在金矿成矿期形成的强硅化蚀变圈，因具有不透水性和强硬的岩石力学性质，造成封闭-半封闭的屏蔽环境，使得猫岭金矿的古元古代成矿特征，包括矿石矿物组成、结构构造、铅同位素和铼-锇同位素组成，以及辽河旋回早期的S1面理得以保存下来，免遭后期的构造-岩浆热事件的改造和破坏。  相似文献   

运动方向的线状指示物与斑变晶中叶理交切轴(FIAs)的比较及其与板块相对运动方向的关系(英文)     

Tim H.Bell 《地学前缘》1999,(3):4

过去还无人指出过板块相对运动的方向与缓倾斜叶理、逆断层和断层上的线状指示物有直接关系,这是因为缓倾斜构造上的运动方向只和变厚了的造山地层的重力塌陷有关,它们和俯冲板块传递给仰冲板块的推力没有关系。缓倾斜叶理上的运动方向的线状指示物和斑状变晶中的叶理弯曲或叶理交切轴（FIA）并无直接关系,这是因为FIA的指向受缓倾斜叶理和斑状变晶边缘上产生的、近乎垂直的叶理之间的交切面控制。在班状变晶边缘上形成的、近乎垂直的叶理在基质中的方位可能在较大范围内变动,因为它们会在稍早期间形成的叶理再活化作用影响下发生转动或遭到破坏。斑状变晶边缘上近乎垂直的叶理,与形成于早期或晚期的缓倾斜叶理的交线,在后期的生长中被圈闭在班状变晶里,此交线规定出了FIA的方位,而与叶理上的运动方向无关。从美国佛蒙特州阿巴拉契亚山脉采集的FIA资料指出,在125km×35km的一片地区内,在该地岩层所发生的多次变形中,从未曾使早期形成的FIA组的方位发生变动。这种情况要求：后来的每一代褶皱都是由于渐进的。总体不均匀缩短作用造成的。这种情况表明：FIA保存着原始的运动方向,此方向未因以后的变形而转动。非洲板块与欧洲板块的相对运动方向和由阿尔卑斯期变质岩中叶理交切轴（FIAs）所指示  相似文献   

辽河(岩)群演化史探讨:以今论古     

仲米山  王海鹏  郭洪方  王忠江  敖光  翟富荣  谭超 《地质与资源》2017,26(5):445-452

通过对太平洋和古亚洲洋演化特征的讨论,可以为辽河（岩）群演化历史研究提供许多宝贵的启示.辽河（岩）群不可能是夭亡的裂谷,至少达到了大西洋阶段和太平洋阶段的洋盆.洋盆的闭合挤压造山作用,是一个漫长的（可能需要数亿年）递进变形过程,在此期间形成的所有构造形迹可归纳为一期构造.辽河（岩）群中的面理,以构造置换面理为主,因此,该套地层不适合按照史密斯地层学原理开展地层学研究,应采用岩性填图方法恢复其本来面貌.  相似文献   

Magnetic Fabric of Cuizhao Pluton and Its Emplacement Significance     

Zhou Weixin 《中国地质大学学报(英文版)》1999,10(3):274-279

1NTRODUCTlONAcloseassociationbetweenthemagneticfabricsofrocksamplesandfieldmicro-structurehasbeenknownbyGraham(l954)andthemagneticsusceptibi1itymethodforstructuralstudieshasbeenusedcommonly(TikoffandTeyssier,l9941Rochetteetal.,1992jYuandZheng,l992;Hrouda,l982).Themagneticfabricsandcomparativepetrofabricstudiesofmanyrockshavebeenexaminedundergoing.Furthermore,thefieldandexperimentsstudiesshowedthat,undercertainconditions,themagneticsusceptibilityanisotropyandfinitestrainarecorrelated,soth…  相似文献   

总体非共轴持续变形产生的构造及其运动学意义——以金州韧性剪切带为例*          下载免费PDF全文

刘如琦  戴立军  王铁军  张鹏程 《地质科学》2009,44(3):825-835

构造解析证实,金州韧性剪切带是以右行走滑为主的大型缓倾斜剪切带,带内发育的糜棱面理-小型褶皱-香肠构造及肿缩构造-S?C组构的系列,以及广泛分布的拉伸线理,是总体非共轴持续变形条件下,带内共轴与非共轴线路相结合的结果,并且后者占主要地位。糜棱面理是最早生成的透入性构造,对其他构造的形成有重要作用。剪应变量(γ)大小与糜棱岩化程度有直接关系。鞘褶皱多发育于γ≥10地段。微构造发育机制的变化是：γ 由低到高,石英变形从低温晶体-塑性转向塑性变形与重结晶作用; 而云母矿物从外形定向转向粘性颗粒-边界滑动。  相似文献   

Patterns of foliation drag near walls of reoriented dykes     

Sudipta Sengupta 《Journal of Earth System Science》1995,104(3):433-446

Drag patterns of foliation are graphically constructed around very competent dykes under bulk strain of pure shear, simple shear and a combination of pure shear and simple shear. Four different types of drag patterns may be produced, depending on the nature of the bulk deformation and the initial orientations of the dyke and the foliation. The drag pattern can be symmetric or asymmetric, inward curving or outward curving. Both the magnitude and the sense of drag may vary along a dyke wall. A uniform sense of drag develops all along a dyke wall only in certain special situations. The type of foliation drag near a dyke may give us a rough idea of the nature of bulk deformation and the relative orientations of the dyke and the foliation with respect to the bulk strain axes.  相似文献