Petrography and geochemistry of clastic sedimentary rocks as evidence for the provenance of the Jurassic stratum in the Daqingshan area

The Daqingshan area is located in the Khondalite belt in the northern margin of the North China Craton. It has the best-preserved Mesozoic basin and is an ideal area for research on Jurassic strata. Sandstones mainly contain quartz and feldspar, with significantly less debris content. In addition, petrography and geochemical classifications have revealed the presence of arkose and wacke. Chondrite-normalized rare earth element patterns of samples are characterized by the enrichment of light rare elements and the flat trend toward heavy rare earth elements. Petrography and source rock discrimination diagrams of geochemical data suggest the presence of felsic rock and Precambrian basement in the northern and southern parts of the basin, which are crucial source areas; however, few mafic materials occur in the Wudanggou Formation. Tectonic discrimination diagrams of geochemical data show that the source materials were deposited on an active continental margin and/or continental island arc. Petrological and geochemical data from the Wudanggou Formation and Changhangou Formation samples suggest that the Yanshan movement influenced the formation of the Changhangou Formation.

Jurassic tectonics of the eastern North China Craton: Response to initial subduction of the Paleo-Pacific Plate

The Yanshan fold-and-thrust belt (YFTB) on the northern margin of the eastern North China Craton (NCC) contains a succession of Jurassic volcano-sedimentary rocks that record the response of the NCC to the initial stages of subduction of the Paleo-Pacific Plate. We present stratigraphic profiles and new zircon U-Pb data from four basins in the YFTB to constrain the ages of the Jurassic lithological units and tectonic events related to the initial subduction. Following uplift at 200–190 Ma, protracted eruption of basalt at 188–167 Ma reflects the earliest tectonic activity in the YFTB. The eruption occurred in a backarc extensional setting, and migrated toward the west, consistent with WNW-directed subduction of the Paleo-Pacific Plate. The measured profiles and geochronological data demonstrate that the earliest phase of shortening in the YFTB during the Jurassic (event A of the Yanshan Movement in the Chinese literature) took place at 167 Ma. This compression terminated the magmatism and extension of the Early–Middle Jurassic, and resulted in the development of local thrusts, regional uplift, and a disconformity, without involvement of intense folding or the development of an angular unconformity. These observations are consistent with a weak to moderate intensity of deformation. The Jurassic rocks in the YFTB record the response of a backarc to the initial stages of subduction of the Paleo-Pacific Plate. Jurassic tectonics in the YFTB and the entire eastern China continent suggests that initial subduction of the Paleo-Pacific Plate began at ca. 190 Ma, and is consistent with the passive margin collapse model.

Tectonic Transformation and Metallogenesis of the Yanshan Movement during the Late Jurassic Period: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Adamellites in Xingcheng, Western Liaoning, China

The Yanshan Movement occurred mainly during the Middle-Late Jurassic, and gave rise to NE trending structures, magmatic events, volcanism and mineral resources. The transformation and evolution of the movement during the Middle-Late Jurassic were investigated from the rock assemblage, geochemistry, and chronology in adamellites which were exposed in the Xingcheng area, western Liaoning. Two types of adamellites were recognized—biotite adamellites with the formation age of 172–168 Ma and garnet-bearing adamellites of 158–152 Ma. All the samples of the two types of adamellites displayed enriched characteristics with high content of SiO2 (66.86–75.55 wt.%) and total alkali (Na2O + K2O = 7.56–8.71 wt.%), high large ion lithophile element (LILE: K, Rb, Sr), and low high field strength element (HFSE: Ce, Ta, P, Ti). The biotite adamellites belong to metaluminous-peraluminous I-type granites, and show volcanic arc granite characteristics, and were formed by partial melting of the ancient crust in the compressional setting that resulting from the subduction of the Paleo-Pacific plate beneath the north margin of the North China Craton (NCC). The garnet-bearing adamellites are also metaluminous-peraluminous I-type granites, with characteristics of both the compressional and extensional regimes, which were formed at the middle-late stages of the continuing subduction of the Paleo-Pacific plate, while simultaneously, the frontal side of the subduction slab began to roll back, leading to an extensional environment. Combining with regional geophysical studies and our petrological and geochemical studies, we propose that the eastern segment of the northern margin of NCC may have been controlled by the Paleo-Pacific tectonic domain at the latest in the Middle Jurassic, while the initiation of the tectonic regime from a compressional to an extensional environment was during the Late Jurassic (158–152 Ma) as a response of the Yanshan Movement. Simultaneously, geochronological statistics of the ore deposits in western Liaoning show that the Mesozoic endogenetic metalliferous deposits formed in a compressive environment influenced by the subduction of the Paleo-Pacific plate, similar to the magma events in ages, and the magmatism provided the thermodynamic condition and the source of metallogenic hydrothermal fluid for mineralization.

Mesozoic Tectonomagmatic Evolution and Gold Metallogeny in Jiaodong Area, East China

There were twice major collision orogenic events in Jiaodong area in Mesozoic period. It showed as three times of magmatic activities and stretching in Jiaodong area. In this paper, based on collecting age datas, referring to the previous classification scheme, a chronological frame pattern of Yanshanian granites had been put forward: Linglong-Kunyushan granite emplacement was in in 160~150Ma; the formation of Guojialing granodiorite was in 130~126Ma; Weideshan granodiorite-granite emplacement was in 120~110Ma; Laoshan A-type miarolitic cavity parlkaline alkali feldspar granite emplacement was in 110~100Ma and represented the end of Yanshan movement. Gold mineralization in three periods in this area had coupled relation with Linglong-Kunyushan granite, Guojialing granodiorite and Weideshan granodiorite-granite. Jiaodong tectonic-magmatic events and gold mineralization were controlled by the interactions among Tethyan tectonic domain, Paleo-ocean tectonic domain and the Pacific tectonic domain.

Subsidence History of Northern Qinshui Basin

Based on the data of coalfield drilling and geological information, using the back-stripping technique, the subsidence history of northern Qinshui basin is studied in this paper. The study shows that this area experienced three stages of subsidence and two stages of uplift since Permo-Carboniferous period. It subsided slowly from Late Carboniferous to middle Permian and then subsided rapidly from Late Permian to Triassic period. It uplifted and denuded from Jurassic period to Cretaceous because of Yanshan movement and continued to uplift and denude since Cenozoic because of Himalayan movement and then subsided from Neocene to Quaternary period. The subsidence center mainly migrated from the south to the north since late Paleozoic. The denudation in the east is more than in the west and the largest denudation thickness is over 1000 m.

The Character of Cretaceous Period's Intrusion in Xinjiang Uygur Autonomous Region

It is regarded that the magmatic activity is over in Upper Hercynides and become stable platform in Mesozoic era in the Shanshan county, Xinjiang province, China. According to the regional geology investigation , rhyolitic porphyry and porphyry granite are broken out. Based on the analysis of rock petrology features, petrochemistry, geochemistry, the latest researches of formation and isotope dating results, it is believed that intrusion is formed in cretaceous period and is the result of Yanshan movement.