Marmarosh massif is an important structural element of the Eastern Carpathians,which differs by the geological features from the other structural-facial zones of Carpathian fold belt.Metamorphic rocks of the massif ha...Marmarosh massif is an important structural element of the Eastern Carpathians,which differs by the geological features from the other structural-facial zones of Carpathian fold belt.Metamorphic rocks of the massif have been formed under the influence of the processes of medium-and low-temperature meta-morphism and metasomatism.Within the Marmarosh massif the stratiform gold ore has展开更多
The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal str...The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal structure is present in Sikkim which is constituted by low to high grade metamorphic rocks characterised by inverted metamorphism. The rocks were repeatedly deformed and were metamorphosed at about 550 to 770℃ (550 to 750MPa). Geologically, the oldest rocks of Eastern Sikkim are represented by Darjeeling Formation showing medium to high grade metamorphism. It is followed by low grade Daling Formation which is characterised by tectonic wedges of Lingtse gneiss. The potassic syenite intrusive i.e. the Sikkim igneous formation is youngest rock type of the area. The Darjeeling Formation associated with amphibolite bands consists of kyanite\|sillimanite, staurolite and garnet zones, while the Daling Formation is characterised by low grade chloritoid and chlorite zones. Lingtse Formation is gneissic in which patches of retrograded and sheared garnet schists are present. Intrusions of potassic syenites (Sikkim Formation) occur in the form of oval and concordant bodies. The F 1, F 2 and F 3 folds are well developed in rocks of Eastern Sikkim area.. The F 1 folds are rootless, tightly isoclinal or reclined and highly obliterated in their attitude. The F 2 folds belong to class IC of Ramsay (1967). Their interlimb angles vary from 20～50 degrees. Intersection lineation due to S 0/S 1 and S 2 surfaces is parallel to the F 2 folds axis. Third generation structures are represented by open to moderately tight and kinked folds. Superimposition of F 3 folds on F 2 folds resulted into type II interference pattern of Ramsay (1967). Structural analysis of these folds have revealed that F 2 folds are non\|cylindrical. The kink or F 3 folds were possibly responsible for the formation of a megakink resembling with the domal structure. The repeatedly deformed rocks of Eastern Sikkim area were folded, faulted, sheared/thrusted during the Himalayan orogeny. The Main Central Thrust (M C T) is actually a ductile shear zone and was subjected to imbrication during later phases of F 2 folding.展开更多
为查明南华系沙坝黄组的沉积环境及时代,对江西高陂地区新发现的火山岩开展野外地质调查、薄片鉴定、岩石地球化学、锆石U-Pb同位素年代学等研究。结果显示,新发现的变质酸性火山岩锆石LA ICP MS U-Pb测定年龄为(727±5)Ma,确定其...为查明南华系沙坝黄组的沉积环境及时代,对江西高陂地区新发现的火山岩开展野外地质调查、薄片鉴定、岩石地球化学、锆石U-Pb同位素年代学等研究。结果显示,新发现的变质酸性火山岩锆石LA ICP MS U-Pb测定年龄为(727±5)Ma,确定其形成时代为南华纪早世,具有高硅、富碱、低镁、低磷、贫钛、过铝质等特征,富集Rb、K、Ba、Zr、Hf等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,轻重稀土分异明显,中等负Eu异常,具有陆相火山岛弧的地球化学特征,暗示其可能形成于造山晚期岛弧海盆拉张环境。展开更多
文摘Marmarosh massif is an important structural element of the Eastern Carpathians,which differs by the geological features from the other structural-facial zones of Carpathian fold belt.Metamorphic rocks of the massif have been formed under the influence of the processes of medium-and low-temperature meta-morphism and metasomatism.Within the Marmarosh massif the stratiform gold ore has
文摘The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal structure is present in Sikkim which is constituted by low to high grade metamorphic rocks characterised by inverted metamorphism. The rocks were repeatedly deformed and were metamorphosed at about 550 to 770℃ (550 to 750MPa). Geologically, the oldest rocks of Eastern Sikkim are represented by Darjeeling Formation showing medium to high grade metamorphism. It is followed by low grade Daling Formation which is characterised by tectonic wedges of Lingtse gneiss. The potassic syenite intrusive i.e. the Sikkim igneous formation is youngest rock type of the area. The Darjeeling Formation associated with amphibolite bands consists of kyanite\|sillimanite, staurolite and garnet zones, while the Daling Formation is characterised by low grade chloritoid and chlorite zones. Lingtse Formation is gneissic in which patches of retrograded and sheared garnet schists are present. Intrusions of potassic syenites (Sikkim Formation) occur in the form of oval and concordant bodies. The F 1, F 2 and F 3 folds are well developed in rocks of Eastern Sikkim area.. The F 1 folds are rootless, tightly isoclinal or reclined and highly obliterated in their attitude. The F 2 folds belong to class IC of Ramsay (1967). Their interlimb angles vary from 20～50 degrees. Intersection lineation due to S 0/S 1 and S 2 surfaces is parallel to the F 2 folds axis. Third generation structures are represented by open to moderately tight and kinked folds. Superimposition of F 3 folds on F 2 folds resulted into type II interference pattern of Ramsay (1967). Structural analysis of these folds have revealed that F 2 folds are non\|cylindrical. The kink or F 3 folds were possibly responsible for the formation of a megakink resembling with the domal structure. The repeatedly deformed rocks of Eastern Sikkim area were folded, faulted, sheared/thrusted during the Himalayan orogeny. The Main Central Thrust (M C T) is actually a ductile shear zone and was subjected to imbrication during later phases of F 2 folding.
文摘为查明南华系沙坝黄组的沉积环境及时代,对江西高陂地区新发现的火山岩开展野外地质调查、薄片鉴定、岩石地球化学、锆石U-Pb同位素年代学等研究。结果显示,新发现的变质酸性火山岩锆石LA ICP MS U-Pb测定年龄为(727±5)Ma,确定其形成时代为南华纪早世,具有高硅、富碱、低镁、低磷、贫钛、过铝质等特征,富集Rb、K、Ba、Zr、Hf等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,轻重稀土分异明显,中等负Eu异常,具有陆相火山岛弧的地球化学特征,暗示其可能形成于造山晚期岛弧海盆拉张环境。
