In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern ...In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone.展开更多
Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pang...Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.展开更多
The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution o...The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution of the Neotethyan ocean as well as the movement of the plates (or blocks) on its two sides, showing as a typical passive continental margin [1] . The Mesozoic and Cenozoic sedimentation forms a giant transgression\|regression cycle in this region [2] . The strata have clearly recorded the processes that the Gondwana continent broke up, the Indian plate drifted northward, and consequently collided with the Eurasia, suggesting a Wilson cycle. They also reveals the evolution of the Neotethyan ocean from breakup to expanding, contracting and finally to closing. 1\ The major sedimentary cycles\;The marine Mesozoic and Cenozoic developed continuously in the northern Himalayas, south Tibet, with a total thickness of about 8000m. From the Triassic to Eocene, 70 third\|order sequences have been recognized [2] . Among them 12 are in the Triassic, 22 in the Jurassic, 27 in the Cretaceous and 9 in the Paleogene, with an average duration of 3m.y for each. These can in turn be grouped as 21 sequence sets and 6 mesosequences (2nd order). All of the mesosequences are bounded by prominent discontinuity at bottom, either with subaerial erosion or submarine truncation [2] , suggesting abrupt falls of sea\|level in long\|term changes. The approximate ages for the basal boundaries of these mesosequences are respectively at ca. 257Ma (latest Capitanian), 215Ma (latest Norian), 177Ma (early Aalenian), 138Ma (mid Tithonian), 103Ma (mid Albian) and 68Ma (late Maastrichtian). Each of mesosequences forms a major sedimentary cycles in the region and may result from the joint effects of global sea\|level changes and regional tectonic\|basin evolution.展开更多
Kekexili basin, located in Northern Qinghai—Xizang plateau, has an area of over 4000km\+2 and is the largest Paleogene land facies basin in the plateau. With NWW\|SEE trend, Kekexili basin extends along the north sid...Kekexili basin, located in Northern Qinghai—Xizang plateau, has an area of over 4000km\+2 and is the largest Paleogene land facies basin in the plateau. With NWW\|SEE trend, Kekexili basin extends along the north side of the Jinshajiang suture. Its sediments, Fenghuoshan group, formed in E 1—E 3, show a shape of wedge with big thickness in south and small thickness in north. There are four sedimentary facies; fan\|delta and alluvial facies that occur in south, lake and lake\|delta facies, which do in north, in this basin. The north\|dipping Jinshajiang normal faults on the south margin of the basin have controlled the developments of the basin. The S—N compression at the end of E3 strongly folded the basin strata and transformed Jinshajiang normal faults into thrusts. In N1, widespread denudation occurred in the whole plateau. During N 2—Q, Kekexili area uplifted along with the whole plateau, besides, the thrusts in the basin showed coherent activity. We propose a geodynamical model for explaining the basin development. In early E,India plate, due to its colliding Eurasia plate, stopped its ocean crust subduction northward, then the subducted ocean lithosphere breaking away made the south margin area, most possibly to the south of Jinshajiang suture, of Eurasia plate isostatically uplift, so the north\|dipping Jinshajiang suture acted as normal faults and controled the north basin development. In late E, the isostatic uplift finished, the basin also gradually terminated its development .At the end of E, Jinshajiang normal faults became thrusts and the basin strata were folded under the northward compression of India plate. In the N1, India plate started incontinental subduction, the lower crust and lower mantle lithosphere of Qinghai—Xizang area underwent more intensive compression and deformation than its upper crust, and the induced transversal expansion in the lower lithosphere uplifted the upper crust and decreased its horizontal stress, which conduced the upper crust undergo denudation. During N 2—Q, convective removal of the lower mantle lithosphere of Qinghai\|Xizang area led to rapid uplift of this area.展开更多
文摘In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone.
文摘Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.
基金theNationalNaturalScienceFoundationofChina (No .4982 5 10 2 )
文摘The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution of the Neotethyan ocean as well as the movement of the plates (or blocks) on its two sides, showing as a typical passive continental margin [1] . The Mesozoic and Cenozoic sedimentation forms a giant transgression\|regression cycle in this region [2] . The strata have clearly recorded the processes that the Gondwana continent broke up, the Indian plate drifted northward, and consequently collided with the Eurasia, suggesting a Wilson cycle. They also reveals the evolution of the Neotethyan ocean from breakup to expanding, contracting and finally to closing. 1\ The major sedimentary cycles\;The marine Mesozoic and Cenozoic developed continuously in the northern Himalayas, south Tibet, with a total thickness of about 8000m. From the Triassic to Eocene, 70 third\|order sequences have been recognized [2] . Among them 12 are in the Triassic, 22 in the Jurassic, 27 in the Cretaceous and 9 in the Paleogene, with an average duration of 3m.y for each. These can in turn be grouped as 21 sequence sets and 6 mesosequences (2nd order). All of the mesosequences are bounded by prominent discontinuity at bottom, either with subaerial erosion or submarine truncation [2] , suggesting abrupt falls of sea\|level in long\|term changes. The approximate ages for the basal boundaries of these mesosequences are respectively at ca. 257Ma (latest Capitanian), 215Ma (latest Norian), 177Ma (early Aalenian), 138Ma (mid Tithonian), 103Ma (mid Albian) and 68Ma (late Maastrichtian). Each of mesosequences forms a major sedimentary cycles in the region and may result from the joint effects of global sea\|level changes and regional tectonic\|basin evolution.
文摘Kekexili basin, located in Northern Qinghai—Xizang plateau, has an area of over 4000km\+2 and is the largest Paleogene land facies basin in the plateau. With NWW\|SEE trend, Kekexili basin extends along the north side of the Jinshajiang suture. Its sediments, Fenghuoshan group, formed in E 1—E 3, show a shape of wedge with big thickness in south and small thickness in north. There are four sedimentary facies; fan\|delta and alluvial facies that occur in south, lake and lake\|delta facies, which do in north, in this basin. The north\|dipping Jinshajiang normal faults on the south margin of the basin have controlled the developments of the basin. The S—N compression at the end of E3 strongly folded the basin strata and transformed Jinshajiang normal faults into thrusts. In N1, widespread denudation occurred in the whole plateau. During N 2—Q, Kekexili area uplifted along with the whole plateau, besides, the thrusts in the basin showed coherent activity. We propose a geodynamical model for explaining the basin development. In early E,India plate, due to its colliding Eurasia plate, stopped its ocean crust subduction northward, then the subducted ocean lithosphere breaking away made the south margin area, most possibly to the south of Jinshajiang suture, of Eurasia plate isostatically uplift, so the north\|dipping Jinshajiang suture acted as normal faults and controled the north basin development. In late E, the isostatic uplift finished, the basin also gradually terminated its development .At the end of E, Jinshajiang normal faults became thrusts and the basin strata were folded under the northward compression of India plate. In the N1, India plate started incontinental subduction, the lower crust and lower mantle lithosphere of Qinghai—Xizang area underwent more intensive compression and deformation than its upper crust, and the induced transversal expansion in the lower lithosphere uplifted the upper crust and decreased its horizontal stress, which conduced the upper crust undergo denudation. During N 2—Q, convective removal of the lower mantle lithosphere of Qinghai\|Xizang area led to rapid uplift of this area.
