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A detailed field-based remote sensing interpretation in this study revealed abundant recent seismic surface ruptures on the southern margin of the Longshoushan Fault, including fault scarps, mole tracks and displacements of river channels. The total length of the surface rupture zone is over 20 km. The most recent vertical and horizontal displacements of the late Quaternary geomorphic markers fall into the range of 0.35~4 m and 0.3~1.9 m, respectively. The southern Longshoushan Fault is a high-angle thrust fault, and it only exhibits left-lateral strike-slip on the west end. Revealed by profile and trench along the surface rupture, the southern branch of the Longshoushan Fault Zone has gone through several earthquake events since the Holocene, and the latest one happened around 3.96 ka. By comparing with the strongest earthquake recorded in this region, it is suggested that the 1954 MS 7¼ Shandan earthquake may have caused the newly discovered surface ruptures, which developed along both the southern and northern branches of the Longshoushan fault zone, presenting a positive flower structure at the shallow surface. This coseismic displacement distribution mostly is found in strike-slip earthquakes in previous studies, but it is found in a thrust earthquake this time. The discovery of coseismic surface rupture on the southern branch of the Longshoushan Fault Zone will throw light on the focal mechanism and rupture pattern of the 1954 Shandan MS 7¼ earthquake.

The Chang 9 oil layer deposits within Ansai District, Ordos Basin, yield considerable reserves of crude oil, yet their source remains ambiguous. This research endeavor was designed to characterize the Chang 9 crude oil and the Chang 7 and Chang 9 source rocks (SRs) of the Yan‐Chang Formation via organic geochemical analysis. The results indicate that the Chang 9 crude oil exhibits a Pr/Ph ratio of 0.84–2.29 and Ga/C30H less than 0.1, implying formed in a weak reduction to weak oxidation freshwater environment. The regular sterane C27‐C28‐C29 configuration assumes an inversed "L" type, reflecting mixed sources and dominant terrestrial plant input. Ratios such as C2920S/(20S + 20R) (0.54–0.6) and C29ββ/(ββ + αα) (0.44–0.58) indicate a mature oil stage. The depositional environment of the C7 and C9 SRs is similar, with weak oxidation to reduction conditions, and consists mainly of Type I and II organics, with a relatively higher maturity of the C9 SRs. A difference in C19/C23TT and C30D/C30H was found between the C7 and C9 SRs. The results show that the C9 crude oils have a similar C19/C23TT with the C9 SRs and similar diahopanes distribution with Class II SRs (C7 and part of the C9 SRs). Thus, the C9 crude oils most likely originate from the C9 SR mixed with the C7 SRs. [ABSTRACT FROM AUTHOR]

The impact of diagenetic minerals and the characteristics of pore structures on reservoir qualities has been studied separately in the past years. However, the difference in the reservoir quality with different pore structures and having same or similar content of diagenesis minerals has not been ascertained. In this study, based on the core samples derived from Chang 6 member in the Ordos basin, various tests were performed to examine the sandstone diagenesis and investigate the pore structure. The results showed that there were five diagenetic facies by diagenetic and pore structure analyses, and the best reservoir quality rocks were found to have relatively low percentage of illite, carbonate cement, pore-filling chlorite, authigenic quartz, and relatively high proportion of intergranular pores. Smectite-to-illite reaction and chemical compaction were main sources for quartz cementation at 60–120°C, and carbonate content was found to increase toward source rocks. The porosity depth trends significantly affected the diagenetic facies. The diagenetic and the pore structure pathways of various diagenetic facies were reconstructed by integrated petrographic, mineralogical, and pore system data. This study provides insights into the porosity evolution and diagenetic pathways of various diagenetic facies of tight sandstones, and the influence of diagenesis minerals and pore structures on their reservoir quality.

The Ordovician Wulalike marine siliceous shale is a notable hydrocarbon source rock in the Northwestern Ordos Basin. However, the causes of quartz and organic matter enrichment are still a mystery to experts. In this study, the organic geochemistry (maceral compositions, Rbitu, and TOC) and elemental geochemistry (major and trace elements) with mineralogy (XRD) and petrography were jointly acquired to systematically investigate the quartz origins and the paleoenvironment, and the main controlling factors for organic matter enrichment in the Wulalike shale. The results show that the organic matter is type I kerogen with low TOC concentrations (average 0.51%), and that the thermal evolution has reached mature and high mature stages (mean Requ is 1.08%). Three types of quartz are developed in Wulalike shale: biogenic quartz (average 63%) is the most dominant, followed by clastic quartz (average 31%) and microcrystalline quartz (average 6%). Babio and Ba/Al values indicate the low paleoproductivity, which is the primary cause for the low TOC found throughout the area. Redox indexes show the anoxic or dysoxic to oxic conditions from the bottom to the top of the section. Paleoclimate and paleowater depth proxies also changed from the bottom to the top. Various paleoenvironments and sedimentological evidence show that Wulalike shale went through the changing environments, and the early sedimentary environments were conducive to organic matter enrichment, leading to a relatively high TOC. The paleoproductivity and preservation conditions have an impact on organic matter enrichment. Based on the results of biogenic quartz distribution and sedimentary environments, it is considered that the bottom of the Wulalike Formation is the most favorable for shale gas exploration and development. [ABSTRACT FROM AUTHOR]

Diagenetic facies play a significant role in the evaluation and prediction of reservoirs as they comprehensively reflect the spatial distribution characteristics of deposition, diagenesis, and petrophysical properties. Based on the petrographic observation and considering pores, lithology, and diagenesis types, the diagenetic facies types were identified, and the pore evolution process and its influence on the quality of low permeability tight gas reservoirs were analyzed. The results show that six types of diagenetic facies were identified, including siliceous cementation intergranular pore facies (A), carbonate dissolution pore facies (B), matrix dissolution pore facies (C), clastic dissolution pore facies (D), matrix filling and strong compaction tight facies (E), and carbonate cementation and metasomatism tight facies (F). The evolution process of porosity shows that the restored original porosity is indicated to be between 34.2% and 36.0%. The average porosity loss caused by compaction was 17.1%, while the average porosity loss caused by cementation is 14.1%. The average porosity increased by 2.5% on diagenetic facies B, C, and D due to dissolution. Consequently, diagenetic facies A with weak compaction and diagenetic facies B, C, and D with strong dissolution are effective reservoirs with porosity greater than 6.6% and permeability greater than 0.25 − 0.6 × 10 − 3 μm2. The distribution areas of A, B, C, and D are favorable areas for tight gas exploration and are important indicators for the prediction of tight gas in the Upper Paleozoic Shanxi Formation in the eastern Ordos Basin. This study provides a new petrographic method for reservoir prediction and exploration of natural gas, which has practical value and economic significance. [ABSTRACT FROM AUTHOR]

The north‐western region of China is one of the five major shale gas evaluation zones in China. The Turpan‐Hami Basin is one of the important petroliferous basins in the north‐west of China. However, shale gas study in this basin has just started. In this study, based on the investigation of the field outcrop section on the periphery and core observation of this basin, combined with extensive experimental analysis, the Permian dark shale has been studied comprehensively including the development distribution characteristics of the shale, brittle mineral composition, organic geochemistry, physical property, and the gas content. The results show that the dark shale are mainly developed in the middle Permian Taerlang Formation and mainly distributed in the Taibei, Toksun, and Tainan sags in the Turpan Depression and the Sanbu and Huoshizhen sags in the Hami Depression. The northern margin and the western margin of the basin and the south of the Liaodun Uplift are exposed to different degrees. Thickness of the dark shale is between 100 and 500 m with the buried depth of 160–3,600 m. The dark shale is mainly deposited in shallow lacustrine and semideep lacustrine facies. The shale is composed mainly of clay minerals (average 44.6%), brittle mineral quartz (average 38.9%), feldspar (average 9.7%), and calcite (average 4.0%). Brittle mineral contents are high, accounting for 52.6%. The dark shale with an organic carbon content more than 2% accounts for 80% in the tested samples. The types of organic matter are commonly Type II2, followed by Type III. The degree of organic thermal evolution is moderate. The majority areas are in the low‐mature and mature stage, while some areas achieve high maturity stage. The gas content ranges from 0.11 to 6.29 m3/t. Comprehensive analysis shows that the Permian Taerlang Formation dark shale in Turpan‐Hami Basin has the shale gas accumulation conditions. The favourable areas are mainly located in the Taibei Sag in the Turpan Depression, the south of the Liaodun Uplift, followed by the Toksun and Tainan sags in the Turpan and the Hami Depressions. [ABSTRACT FROM AUTHOR]

A saline lake developed in the Ningnan Basin during the sedimentation of the Qingshuiying Formation in the Late Paleogene. In order to research the evolutionary characteristics of the saline lake and its response effect to the regional paleoclimate and uplift of the Tibetan Plateau in the Late Paleogene, the Hejiakouzi section of Qingshuiying Formation in the north of the Ningnan Basin was selected. The features of the strata, gypsum petrology, and S and Sr isotopes of synsedimentary gypsum were studied. Furthermore, the relationship of the evolution of the saline lake to the regional paleoclimate and the uplift of the Tibetan Plateau are discussed. The results showed that the lithology of Qingshuiying Formation was mainly celadon‐aubergine mudstone and gypsum. S and Sr isotopic values of synsedimentary gypsum were 8.2–12.3‰ and 0.7105–0.7113, respectively. The sedimentary environment of Qingshuiying Formation was generally a weak continental saline lake, which can be further divided into 4 kinds of sedimentary environment, namely deep saline lake, semi‐deep saline lake, shallow saline lake, and brackish lake. At 45–40 Ma, the first uplift of the Tibetan Plateau occurred with a humid climate, and a brackish lake was mainly germinated. At 40–30 Ma, the climate was dry and hot, and deep and semi‐deep saline lakes mainly developed. At 30–27 Ma, the climate became dry and cold, and a shallow saline lake mainly developed. At 27–23 Ma, the second uplift of the Tibetan Plateau occurred, the climate became humid and cold due to the East Asian summer monsoon, and a brackish lake mainly developed, and the evolution of saline lake was completed by this time. [ABSTRACT FROM AUTHOR]

The Mengxi porphyry copper deposit, situated in the eastern Junggar, Central Asian Orogenic Belt, is not a typical porphyry copper deposit, and the origin of the deposit has been a topical debate for a decade. The ore bodies of the Mengxi porphyry copper deposit mainly developed in the volcanic‐sedimentary terrane (Huangcaopo Group) near a granite porphyry, with strong wall‐rock alteration as well as vertical zonation and fracture‐related vein fillings. The result of zircon U–Pb dating indicates that the granite porphyry was emplaced at 432.6 ± 6.7 Ma. The granite porphyry has relatively low initial 87Sr/86Sr ratios (0.70465–0.70537), high whole‐rock ƐNd(t) values (−2.2 to 6.6), and similar geochemical affinities of adakites and Andean island arc volcanic rocks, indicating that the Mengxi granite porphyry was derived from the partial melting of the upper mantle modified by slab‐derived fluids, with negligible assimilation of crust. Pyrites from the porphyry and volcanic‐sedimentary terrane have a similar δ34S and Pb isotopic compositions, indicating that different pyrites may have similar source. Based on the detailed field investigation, observed mineral assemblages, and crosscutting relationships, massive fine anhedral chalcopyrite and bornite disseminated in the Huangcaopo Formation, chalcopyrite as inclusion in pyrite veins in the contact zone, and the amount of Cu‐bearing minerals increased from terrane to veins have been recognized. All these observations reveal that the ore‐forming materials of the Mengxi copper deposit were mainly derived from the metasomatic alteration of the Huangcaopo Group triggered by the extensive Early Devonian tectonic‐magmatic events. [ABSTRACT FROM AUTHOR]

The southwestern area of the Ordos Basin, China, contains good oil/gas systems, similar to the main basin. However, no oil/gas reserves have been found because some magmatic rocks with different occurrences developed in the region, it resulted in the suspension of oil/gas exploration in the 1980s. By means of integrated research based on field investigation, geophysical interpretation, and data of drilling wells, this paper indicates that magmatic activities in the southwestern Ordos Basin display different properties over multiple periods. The Proterozoic and Palaeozoic magmatic rocks are mainly distributed as a large batholith in the Qinling Orogen, and the Qilian Orogen around the southwestern margin of the Ordos Basin. These Proterozoic and Paleozoic plutons have no effect on hydrocarbon source rocks and oil/gas generation in the Ordos Basin. However, the Mesozoic magmatic activities developed within the basin have obvious effects on oil/gas generation. Three kinds of exploration regions were selected within the southwestern Ordos Basin according to the distribution of hydrocarbon source and magmatic rocks as well as the thermal degree: (a) the marginal area of the basin, (b) the region of the Longmen Uplift distributed with concealed magmatic rocks within the basin, and (c) the region within the basin far away from concealed magmatic rocks. Three sets of gas source rocks, that is, the Upper Proterozoic algal dolostone, the Middle Ordovician dark shale, the Upper Paleozoic black mudstone of coal system, and one set of oil source rocks of the Upper Triassic lacustrine black mudstone and oil shale, are exposed in outcrops near the margin of the basin. They all display a low thermal degree with vitrinite reflectance (Ro) below 1.3%, and they do not contribute to oil/gas accumulation because of earlier tectonic uplift. The gas source rocks and oil source rocks, which occur within the basin area of the Longmen Uplift, where the concealed magmatic rocks, display an abnormal thermal degree of over maturation with Ro over 3.4% and underwent dry gas generation because of heating from magmatic activity, and they have gas exploration potential. The source rocks distributed within the basin area away from concealed magmatic rocks display a normal thermal degree and oil/gas generation. The Ro of the Upper Triassic oil source rock is 1.0–1.6%, which is under the thermal maturity stage of liquid oil generation, whereas that of the Upper Paleozoic gas source rocks is 2.0–2.5% under the thermal maturity stage of gas generation. Measured Ro and burial depth of source rocks in the region show a linear relationship, which indicate that source rocks experienced thermal evolution and oil/gas generation under the normal burial thermal condition rather than the magmatic activity. This region has the most potential for both oil and gas exploration. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Jixian System is widely distributed at the south‐western margin of the Ordos Basin. It is mainly dominated by siliceous laminated algal micritic dolomite that is a set of potential carbonate source rocks. The magmatic activities at the south‐western margin of the Ordos Basin were frequent and intensive, and the Tongcheng intrusion exposed in this area has an intrusive contact relationship with the Jixian System. This paper uses geochemical methods to study the influence of magmatism to lithology, physical properties, hydrocarbon generating property, and geochemistry of the Jixian System. Analysis data reveal that, with the increasing distance to the intrusion, the porosity, permeability, and content of dolomite, trace elements, and rare earth elements in surrounding rock decrease while the density and silica content increase gradually. In addition, the parameters have a weakening trend about adsorbed hydrocarbon (S1), pyrolysis hydrocarbon (S2), hydrocarbon generating potential (S1 + S2), and pyrolysis peak temperature (Tmax). The results suggest that the magmatic hydrothermalism and the thermal effect of magmatic intrusion changed the physical and geochemical characteristics of the surrounding rock and promoted the hydrocarbon generation of organic matter. However, these characteristics reflect that the magmatic activities only have a relatively small effect on the laminated algal micritic dolomite in Jixian System without a destructive effect at the south‐western margin of the Ordos Basin. The petroleum potential of the Jixian System is worthy to be further explored. [ABSTRACT FROM AUTHOR]

The raindrop method of searching a solution space for feasible and efficient forest management plans has been demonstrated as being useful under a limited set of circumstances, mainly where adjacency restrictions are accommodated using the unit restriction model. We expanded on this work and applied the model (in a modified form) to a problem that had both wood flow and area restriction adjacency constraints, then tested the problem formulation on six hypothetical forests of different sizes and age class distributions. Threshold accepting and tabu search were both applied to the problems as well. The modified raindrop methodâs performance was best when applied to forests with normal age class distributions. 1-opt tabu search worked best on forests with young age class distributions. Threshold accepting and the raindrop method both performed well on forests with older age class distributions. On average, the raindrop method produced higher quality solutions for most of the problems, and in all but one case where it did not, the solutions generated were not significantly different than the heuristic that located a better solution. The advantage of the raindrop method is that it uses only two parameters and does not require extensive parameterization. The disadvantage is the amount of time it needs to solve problems with area restriction adjacency constraints. We suggest that it may be advantageous to use this heuristic on problems with relatively simple spatial forest planning constraints, and problems that do not involve young initial age class distributions. However, generalization of the performance of the raindrop method to other forest planning problems is problematic, and will require examination by those interested in pursuing this planning methodology. Given that our tests of the raindrop method are limited to a small set of URM and ARM formulations, one should view the combined set of work as additional insight into the potential performance of the method on problems of current interest to the forest planning community.