A key issue in orogenic research today is the recognition and explanation of normal faulting in the heart of collisional mountain belts. The active Himalayan system remains an ideal locality for studying this phenomen...A key issue in orogenic research today is the recognition and explanation of normal faulting in the heart of collisional mountain belts. The active Himalayan system remains an ideal locality for studying this phenomenon, both as E—W synconvergent extension of the Tibetan plateau and normal motion on the South Tibetan Detachment System (STDS). However, these processes are difficult to correlate with the evolution of the northwest Himalaya, particularly the Nanga Parbat syntaxis where a Neogene tectono\|thermal overprint partially obscures the early collisional history. An integrated programme of structural mapping, petrography, thermobarometry and isotopic dating is presented that places important constraints on both the early\| and pre\|Himalayan evolution of the syntaxis. These data include evidence for synconvergent, ductile extension predating syntaxis development, and improved isotopic correlation of the tectonic units with the familiar central Himalayan thrust sheets, building on the work of Whittington et al (1999).Recent studies have focused on the rapid exhumation of the Nanga Parbat\|Haramosh Massif (NPHM) during the last 10Ma, and the related Neogene thermal effects dominating the core of the massif (e.g. Zeitler et al. 1982, 1993). However, the degree of both structural and metamorphic Neogene overprinting varies within the massif, becoming weaker away from the summit region. In addition, the considerable variation in rock\|type outside the gneissic core results in both strain partitioning and various degrees of metamorphic reworking. Thus several workers (e.g. Wheeler et al. 1995) could reconstruct elements of the early and pre\|Himalayan history from field relations and mineral assemblages virtually untouched by Neogene processes. The eastern margin of the massif, in contrast to the active western margin, has remained largely unchanged during the Neogene, except for essentially passive rotation on the limb of the major syntaxial antiform. The original, ductile Main Mantle Thrust (MMT), which emplaced the Ladakh Island Arc (LIA) over the Indian margin in the late Cretaceous, is preserved in a steepened orientation. Dextral shear sense indicators in this steep fabric can be clearly related to southward thrusting on the MMT at peak metamorphic conditions during the early Himalayan stage (600～700°C and 900～1200MPa) once the N—S trending syntaxial antiform is unfolded.展开更多
The origin of sandstone in the Rawalpindi group is disputed because of the lesser Himalayas complicated geological structure and ongoing tectonic activity. The goal of the study is to learn more about the petrographic...The origin of sandstone in the Rawalpindi group is disputed because of the lesser Himalayas complicated geological structure and ongoing tectonic activity. The goal of the study is to learn more about the petrographic and geological aspects of the Siwalik molasses deposits, which are formations that belong to the same age group. The Early Miocene Kamlial Formation, the Middle to Late Miocene Chinji Formation, and the Late Miocene Nagri Formation are the stratigraphic units revealed in the project area. The texture of the sandstone found in the Rawalpindi Group and Siwalik is fine to medium-grained. The hue ranges from grey to greenish grey. The sandstone displays thin to medium-bedded layers and exhibits thin lamination throughout. The sandstone of the Kamlial Formation contains load casts, potholes, worm burrows, hematite layers, and filled and unfilled mud cracks in basic structures. Model petrographic research reveals that the Murree Formation primarily consists of light minerals like feldspar, quartzite, and felice, whereas the Kamlial Formation is composed of heavy minerals like garnet and tourmaline. Sandstone from the Rawalpindi group undergoes analysis to ascertain its provenance using the quartz feldspar lithic fragments ternary diagram technique. Each plot in the QFL diagram’s recycled orogeny provenance field is plotted.展开更多
The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurre...The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurrence of basins as en chelon arrangement suggests that they were formed under tectonic setting of right\|lateral strike\|slip. The north termination of main faults controlling basins deposition and evolution, meet the Red River fault as an acute angle. The Lanping basin, one representative of all basins, is chosen to study its formation mechanism. Facts of rapid lateral phase change, sediment offset from their source and lateral migration of alluvial fan, indicate that the Lanping basin is a strike\|slip basin and its boundary main fault is syndepositional left\|lateral strike\|slip normal fault. Basin formation was controlled by mechanism of strike\|slip and pull\|apart, the Lanping basin belongs to extension strike\|slip basin. The nature of the Lanping basin and infill suggest that the boundary fault controlling basin deposit was formed during right\|lateral strike\|slip deformation of the Red River fault. Whether formation mechanism of single basin or occurrence of basins supported that the Red River fault was a right\|lateral strike\|slip fault during the Paleocene\|middle Eocene.展开更多
文摘A key issue in orogenic research today is the recognition and explanation of normal faulting in the heart of collisional mountain belts. The active Himalayan system remains an ideal locality for studying this phenomenon, both as E—W synconvergent extension of the Tibetan plateau and normal motion on the South Tibetan Detachment System (STDS). However, these processes are difficult to correlate with the evolution of the northwest Himalaya, particularly the Nanga Parbat syntaxis where a Neogene tectono\|thermal overprint partially obscures the early collisional history. An integrated programme of structural mapping, petrography, thermobarometry and isotopic dating is presented that places important constraints on both the early\| and pre\|Himalayan evolution of the syntaxis. These data include evidence for synconvergent, ductile extension predating syntaxis development, and improved isotopic correlation of the tectonic units with the familiar central Himalayan thrust sheets, building on the work of Whittington et al (1999).Recent studies have focused on the rapid exhumation of the Nanga Parbat\|Haramosh Massif (NPHM) during the last 10Ma, and the related Neogene thermal effects dominating the core of the massif (e.g. Zeitler et al. 1982, 1993). However, the degree of both structural and metamorphic Neogene overprinting varies within the massif, becoming weaker away from the summit region. In addition, the considerable variation in rock\|type outside the gneissic core results in both strain partitioning and various degrees of metamorphic reworking. Thus several workers (e.g. Wheeler et al. 1995) could reconstruct elements of the early and pre\|Himalayan history from field relations and mineral assemblages virtually untouched by Neogene processes. The eastern margin of the massif, in contrast to the active western margin, has remained largely unchanged during the Neogene, except for essentially passive rotation on the limb of the major syntaxial antiform. The original, ductile Main Mantle Thrust (MMT), which emplaced the Ladakh Island Arc (LIA) over the Indian margin in the late Cretaceous, is preserved in a steepened orientation. Dextral shear sense indicators in this steep fabric can be clearly related to southward thrusting on the MMT at peak metamorphic conditions during the early Himalayan stage (600～700°C and 900～1200MPa) once the N—S trending syntaxial antiform is unfolded.
文摘The origin of sandstone in the Rawalpindi group is disputed because of the lesser Himalayas complicated geological structure and ongoing tectonic activity. The goal of the study is to learn more about the petrographic and geological aspects of the Siwalik molasses deposits, which are formations that belong to the same age group. The Early Miocene Kamlial Formation, the Middle to Late Miocene Chinji Formation, and the Late Miocene Nagri Formation are the stratigraphic units revealed in the project area. The texture of the sandstone found in the Rawalpindi Group and Siwalik is fine to medium-grained. The hue ranges from grey to greenish grey. The sandstone displays thin to medium-bedded layers and exhibits thin lamination throughout. The sandstone of the Kamlial Formation contains load casts, potholes, worm burrows, hematite layers, and filled and unfilled mud cracks in basic structures. Model petrographic research reveals that the Murree Formation primarily consists of light minerals like feldspar, quartzite, and felice, whereas the Kamlial Formation is composed of heavy minerals like garnet and tourmaline. Sandstone from the Rawalpindi group undergoes analysis to ascertain its provenance using the quartz feldspar lithic fragments ternary diagram technique. Each plot in the QFL diagram’s recycled orogeny provenance field is plotted.
文摘The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurrence of basins as en chelon arrangement suggests that they were formed under tectonic setting of right\|lateral strike\|slip. The north termination of main faults controlling basins deposition and evolution, meet the Red River fault as an acute angle. The Lanping basin, one representative of all basins, is chosen to study its formation mechanism. Facts of rapid lateral phase change, sediment offset from their source and lateral migration of alluvial fan, indicate that the Lanping basin is a strike\|slip basin and its boundary main fault is syndepositional left\|lateral strike\|slip normal fault. Basin formation was controlled by mechanism of strike\|slip and pull\|apart, the Lanping basin belongs to extension strike\|slip basin. The nature of the Lanping basin and infill suggest that the boundary fault controlling basin deposit was formed during right\|lateral strike\|slip deformation of the Red River fault. Whether formation mechanism of single basin or occurrence of basins supported that the Red River fault was a right\|lateral strike\|slip fault during the Paleocene\|middle Eocene.
