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In the Qaidam basin, Northwest China, karstic fissures and caves are developed in many places of the Lower Carboniferous Chengqianggou Fm. and Huaitoutala Fm. and the Upper Carboniferous Keluke Fm., in which are found typical karstic marks. Several suites of transgressive carbonate rocks formed during the Late Paleozoic epoch are preserved as reservoir properties in the Qaidam basin, with paleokarst‐related cave‐fractured diagenetic structures, which provided the basis for cave‐fractured development. Carbonate and clastic samples covering or infilling caves and fractures in Carboniferous strata were collected in the eastern Qaidam basin to focus on petrological and geochemical analyses of karst and infilling materials. Based on this study of the Caledonian diagenetic sequence, and bitumen‐infilled inclusion temperature and burial history, there existed a continuous atmospheric freshwater leaching process, which played a critical role in the construction of the Carboniferous supergene paleokarsts. Investigation and survey of the tectonic setting, plate paleolatitude and river development intensity also proves that there was abundant rainfall during the Indosinian period, after which the strata undergo a shallow burial process. Because Indosinian period is earlier than the key timing of hydrocarbon‐generation of the Carboniferous source rocks, this kind of karst reservoir has potential significance for oil‐gas resources in this area. [ABSTRACT FROM AUTHOR]

The Jurassic sequence in the northern Qaidam Basin can be represented by the lower coal‐bearing swamp‐lacustrine sediments unit and the upper reddish clastic deposits suite, which recorded dramatic transition of deposit environment changes. Whole‐rock geochemical data of this succession in Dameigou profile were used to reconstruct the provenance and chemical weathering history. Based on the major element discrimination diagrams, trace element ratios and chondritenormalized REE patterns, most sediments were derived from a similar source area with felsic‐intermediate rocks as dominant contributors. Multiple geochemical parameters and index displayed good correlation, via vertical variations sequence, Jurassic chemical weathering history of northern Qaidam Basin was established, and four stages were recognized from the profile. Phases I and III experienced intense chemical weathering, while Phases II and IV are characterized by mild to moderate chemical weathering. Based on this, long‐term Jurassic climatic evolution of the Qaidam Basin was reconstructed. Early‐middle period of Early Jurassic and middle period of Middle Jurassic developed warm and humid climate. On the contrary, late Early Jurassic‐early Middle Jurassic and late Middle Jurassic‐Late Jurassic was deposited under relatively semiarid to arid climatic conditions. [ABSTRACT FROM AUTHOR]

The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well-known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high-angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high-angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip-slip was 1.67-2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid-Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging-wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall. [ABSTRACT FROM AUTHOR]

Shale gas is a resource of emerging importance in the energy field. Many countries in the world have been making big financial investments in this area. Carboniferous shale in the eastern Qaidam Basin shows good exploration prospects, but limited research and exploration work for shale oil and gas resources has been undertaken. Geochemical analyses were performed on shale derived from the Upper Carboniferous Hurleg Formation in the eastern Qaidam Basin, Qinghai Province, and secondary electron imaging capability of a Field Emission scanning electron microscope (FE-SEM) was used to characterize the microstructure of the shale. The reservoir and exploitation potential of the studied shale was assessed by comparison with research results obtained from the Barnett Formation shale in Fort Worth Basin, North America and the Basin shale of Sichuan province. The results indicate that the eastern Qaidam Basin Carboniferous shale is high-quality source rock. There are four major microstructural types in the study area: matrix intergranular pores, dissolution pores, intergranular pores, and micro-fractures. The size of the micropores varies from 6-633 nm, the majority of which is between 39-200 nm, with a relatively small number of micro-scale pores ranging from 0.13-1 μm. The pore characteristics of the studied shales are similar to the North American and Sichuanese shales, indicating that they have good reservoir potential. No micropores are present in the organic matter, which is induced by its composition; instead we found an important lamellar structure in the organic matter. These micropores and microfractures are abundant, and are connected to natural visible cracks that form the network pore system, which controls the storage and migration of shale gas. This connectivity is favorable for shale gas exploitation, providing great scientific potential and practical value. [ABSTRACT FROM AUTHOR]

Abstract: The Miyun Geopark is located in the northern part of the North China Craton and includes a variety of Archean granitoids and metamorphic rocks. SHRIMP zircon dating documents their emplacement ages at 2567–2508Ma, metamorphic events at ca. 2.50Ga, 2.44Ga, and 1.82Ga. Late Neoarchean basement rocks elsewhere in the North China Craton document a similar evolutionary history with intrusion of granitoid rocks commencing at ca. 2590Ma and reaching three peaks at about 2550, 2520, and 2500Ma; these rocks then underwent regional metamorphisms at ca. 2.50Ga, 2.44Ga, 1.92Ga, and 1.82Ga. Positive ε Hf(t) values of +1.7 to +7.6, with model ages younger than 3.0Ga, for magmatic zircons from these late Neoarchean intrusive rocks indicate that they are predominantly derived from juvenile crustal sources and suggest that significant crustal growth occurred in the northern North China Craton during the Neoarchean. The intrusive rocks in the Miyun area are part of an extensive province of late Neoarchean magmatism and appear to be related to mantle plume activity at this time. [Copyright &y& Elsevier]

Cet article présente les ruptures de terrain déclenchées par le séisme du Kunlun central, de magnitude Ms 8,1. Il s’est développé le long de la zone de faille active du Kunlun oriental, connue pour enregistrer un mouvement de cisaillement sénestre de 10 à 20 mm/an. La rupture s’est développée sur une zone de 426 km de long avec un glissement sénestre atteignant 16,3 m, l’un des plus importants déplacements de ce type enregistré en zone continentale. L’article décrit les fractures, les dislocations des terrains, les structures en horst, les dépressions, les escarpements et les phénomènes de liquéfaction observés et discute des risques de futurs événements sismiques le long de la ligne de chemin de fer Qinghai–Tibet actuellement en construction. [ABSTRACT FROM AUTHOR]

The article focuses on study and search for reefs during the hydrocarbon evaluation of Paleozoic marine carbonate rocks in the Qaidam Basin, China. It mentions evolution of the carboniferous reef with important hydrocarbon reservoirs and geological survey confirmed the existence of Paleozoic reef skeletons in the Qaidam Basin. It also mentions analyses of sedimentary petrology, reef species identification, inclusion temperature and burial history of the Early Carboniferous reefs.

China's complete late Mesozoic continental sedimentary records are advantaged condition for related land-based climatic history research. Qaidam Basin located at the northern margin of Tibetan Plateau, its late Mesozoic strata provides important information about palaeoenvironment change. Several significant geologic events such as the collision of Bangong-Nujiang Suture and the interior aridification appearance at NW China are likely recorded in the succession, which makes it an ideal window of palaeoclimate investigation. Through the recent study, the Late Jurassic-Early Cretaceous eolian deposits have been discovered from the overlying strata of Hongshuigou Formation in Wanggaxiu area, Qaidam Basin. The typical eolian evidences can be identified in both rock micro-structure and depositional features: the strata mainly consist of brown medium pure sandstone with well sorting-good round quartz. Obvious eolian grain surface textures such as dish-shaped impact crater, crescent-shaped impact scars can be observed through SEM. Well-developed thick, large scale and high dip tabular cross-bedding characterized by eolian dune foresets. The synsedimentary deformation structures are common in eolian strata, such as drag folds and overturned folds. According to lithology and sedimentary structure characteristics, 4 subfacies were recognized in the Wanggaxiu eolian deposits. The dune subfacies was characterized by large-scale cross bedding. Waddy, inter dunes and desert lake were feat ure as aqueous deposit. The discovery of Wanggaxiu eolian strata has enriched sedimentary types in the Mesozoic Qaidam Basin. and is of certain significances for the study of regional sequncces, Late Mesozoic paleoclimatic and paleogeographic evolution of the northwest China. [ABSTRACT FROM AUTHOR]

The article focuses on a research on the discovery of Palaeozoic Karsts in the Qaidam Basin and their oil and gas prospects. Topics discussed include constraining of the oil and gas exploration in the Paleozoic strata of the Qaidam Basin due to complex geological factors; conducting field outcrop observations and detailed old well surveys and studying paleokartst indicators, distribution and hydrocarbon properties; and Carboniferous Chengqianggou and Huaitoutala Formations in the basin.

Two active faults, including the Huashan piedmont fault (HPF) along the northern margin of Huashan Mountain and the north margin fault of the Weinan loess tableland (NMF-WLT), were developed in the southeastern Weihe Graben, in central China. HPF, which is the most active fault in the Weihe Graben, is known throughout the world for the M8 1 / 4 great Guanzhong earthquake in 1556 AD. Through field investigation, AMS 14 C, and OSL dating in this paper, in combination with previous studies, the following results are obtained: (i) Tectonic landforms, such as triangular fault facets, waterfalls and fault scraps of proluvial fans, were developed in the HPF, but these features were not developed in the NMF-WLT. (ii) HPF experienced three intensive seismic activities in 5920–7670 Cal yr BP, 2215 ± 95–3105 ± 105 Cal yr BP and 1556 AD during the Holocene, but there has only been one seismic event noted for the NMF-WLT since the Holocene (6865 ± 80 Cal yr BP). (iii) The dip-slip rate of the HPF was approximately 0.64 mm/yr since the mid-Pleistocene and approximately 1.67–2.71 mm/yr in the Holocene. In contrast, the dip-slip rate of NMF-WLT was approximately 0.32–0.42 mm/yr since the early Pleistocene and was approximately 0.39–0.58 mm/yr from the late Pleistocene to the Holocene. (iv) The seismic activity at the HPF has been more intense than at the NMF-WLT; the HPF was the triggering seismic fault of the M8 1 / 4 great Guanzhong earthquake in 1556 AD, whereas the NMF-WLT was not the seismogenic fault of this event. These results provide new information for the study of active tectonics of the Weihe Graben. [ABSTRACT FROM AUTHOR]