• Volume 95,Issue 4,2021 Table of Contents
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    • ORIGINAL ARTICLES

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    • First Record of Petalodus Owen, 1840 (Chondrichthyes, Petalodontidae) in the Lower Permian (Cisuralian) of China

      2021, 95(4):1057-1064. DOI: 10.1111/1755-6724.14784

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      Abstract:The Petalodontiformes are a small intriguing group of Permo–Carboniferous chondrichthyans. Petalodus is the longest known petalodont genus generally considered representative of the order. The first definite fossil record of seven well-preserved Petalodus teeth has been found in the Qianshi limestone in the Lower Permian (Cisuralian) middle–upper Taiyuan Formation in Yangquan City, Shanxi Province, North China. The specimens are characterized by petal-shaped teeth with a spade-like crown, and a long, tongue-shaped root; the crown is circled with a band or cingulum composed of imbricated ridges at the base. All seven teeth are assigned to the species P. ohioenesis because of their vertically narrow cingulum and much longer root. Petalodus is a worldwide genus, with fossil localities mainly concentrated in the Laurussia supercontinent. The occurrence of Petalodus teeth in Yangquan not only is the first fossil record in China, but also only the second record in Asia. The Yangquan fossil site was part of the paleoequatorial North China Craton during the Early Permian, and was isolated from Laurusia and East Gondwana by the Paleo-Tethys Ocean. The successful dispersal of Petalodus from Laurusia to the North China Block along Paleo-Tethys may support the possibility that Petalodus taxa were active free-swimmers rather than bottom dwellers. The new finding increases the petalodont diversity in eastern Asia, and also sheds new light on the distribution and stratigraphic range.

    • First Discovery of Dicerorhinus sumatrensis from Yanjinggou Provides Insights into the Pleistocene Rhinocerotidae of South China

      2021, 95(4):1065-1072. DOI: 10.1111/1755-6724.14719

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      Abstract:The Rhinocerotidae is one of the most common and important families in the Pleistocene mammalian fauna of South China. Since the last century, most of the Pleistocene rhinocerotid fossils were prematurely assigned to Rhinoceros sinensis, which has resulted in confusion of taxonomy for decades, especially in South China. The Yanjinggou area in Chongqing Municipality of China, where the neotype of R. sinensis came from, has yielded abundant rhinocerotid fossils and is a key area to solve this problem. A recently discovered juvenile skull from a karstic fissure in this area can be referred to Dicerorhinus sumatrensis (Fischer, 1814), which is the first confirmed non-Rhinoceros rhinocerotid from the area. This new finding indicates that non-Rhinoceros fossils might have been mixed in AMNH collection from Yanjinggou and thus the diagnosis of Rhinoceros sinensis needs reformation. On the other hand, Stephanorhinus ?kirchbergensis is also detected in Granger’s collection based on our reobservation. The coexistence of Rhinoceros, Dicerorhinus and Stephanorhinus shows the higher diversity of Pleistocene rhinocerotids in South China.

    • Revision to Kowalskia from the Houhecun Fauna and a New Discovery of Tscherskia (Cricetidae, Rodentia) from the Youhe Fauna of Weinan, Shaanxi Province, China

      2021, 95(4):1073-1079. DOI: 10.1111/1755-6724.14776

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      Abstract:The fossil hamster (an isolated m1) from the early Early Pleistocene Houhecun fauna found in Dali, Weinan, Shaanxi, China, originally identified as Kowalskia dalinica, is reexamined. Its unique characters, including a high crown, very small degree of division of the anteroconid and relatively large size, is taken as evidence of its attribution to the genus Sinocricetus, instead of Kowalskia (junior synonym of Neocricetodon) suggested by the original author. Therefore, the specific name of the species established based on this m1 should be changed to S. dalinicus (Wang, 1988). S. dalinicus probably has a relatively close affinity with S. major Li, 2010, but there are still some obvious differences of characters between them. The discovery of S. dalinicus in the Houhecun fauna confirms that the genus indeed survived into the Pleistocene. A broken hamster mandible, which was found in Weinan, Shaanxi, China and belongs to the late Pliocene Youhe fauna, is also described here and identified as Tscherskia sp.. This specimen represents the earliest Tscherskia in Asia so far, but fails to refute the hypothesis that the genus originated in Europe during the early Pliocene.

    • On the Validity and Evolution of Assilina Species during the Ypresian–Lutetian: Example from Bir Dakhl, Eastern Desert, Egypt

      2021, 95(4):1080-1085. DOI: 10.1111/1755-6724.14424

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      Abstract:The genus Assilina is a taxon within the Nummulitacea that appeared early in the Ypresian (Early Eocene) and continued until the end of the Lutetian (Middle Eocene). Thus, this taxon could be useful for the chronostratigraphy of this time interval. Lower Eocene rocks in southern Galala, Egypt are exposed at Bir Dakhl. This section includes marl sediments with debris flow shallow-marine facies deposits laid down during early Eocene times and includes fossils of large foraminifera: Assilina placentula Deshayes, 1838 and Nummulites burdigalensis de la Harpe, 1926. These are systematically treated, described and illustrated. Nummulites burdigalensis belongs to the N. burdigalensis group, and Assilina placentula belongs to the group of Assilina exponens. This assumption is based on qualitative morphology and quantitative measurements. Both species, together with Operculina libyca Schwager, 1883, enable the assignment of the Bir Dakhl (D5-40 Section) to the Early Eocene, Ypresian (SBZ10 of Serra- Kiel et al., 1998) supporting an earlier opinion that Assilina placentula belongs to that zone in the calibrated larger foraminiferal biostratigraphic zonation.

    • Geochemistry and Tectonic History of Seamount Remnants in the Xingshuwa Subduction Accretionary Complex of the Xar Moron Area, Eastern Margin of the Central Asian Orogenic Belt

      2021, 95(4):1086-1098. DOI: 10.1111/1755-6724.14646

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      Abstract:This study focuses on the geology, geochemistry, zircon U-Pb geochronology and tectonic settings of the three types of seamount basalts from the Xingshuwa subduction accretionary complex in the Xar Moron area, eastern margin of the Central Asian Orogenic Belt (CAOB). The seamount remnants are composed of carbonate ‘cap’ sediments, large volumes of pillow and massive basalts, carbonate breccia slope facies and radiolarian cherts. Group 1 basalts are characterized by high contents of P2O5 and TiO2 with alkaline affinity and LREE enrichment, indicating that they are derived from intraplate magma. Group 2 basalts display N-MORB LREE depletion patterns, indicating that they were formed at a mid-ocean ridge. Group 3 basalts have shown distinct Nb depletion and high Th/Yb ratios, indicating that they were generated in an island arc tectonic setting. The zircon U-Pb age of Group 1 basalt sample XWT18-131 is 576.4 ± 9.4 Ma, suggesting that the oceanic island seamount was the product of intraplate magmatism related to a mantle plume or ‘hot spot’ in the late Neoproterozoic. The zircon U-Pb age of Group 2 basalt sample XWT18-132 is 483 ± 22 Ma, indicating that the Paleo-Asian Ocean (PAO) was continuously expanding in the Early Ordovician. The zircon U-Pb age of Group 3 basalt sample XWT18-101 is 240.5 ± 8.2 Ma, suggesting that this area underwent the evolutionary path of ocean-continent transition, developing towards continentalization during the Middle Triassic. Thus, we believe that there was both mantle plume-related intraplate magmatism and intraoceanic subduction during the evolution of the PAO, the CAOB possibly being an evolutionary model of an intraoceanic subduction and mantle plume magmatism complex.

    • Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Junggar, NW China

      2021, 95(4):1099-1111. DOI: 10.1111/1755-6724.14420

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      Abstract:Seamount accretion is one of the most significant accretionary orogenic processes in the Central Asian Orogenic Belt, but there are few paleo-seamounts reported from and debate on the tectonic evolution of the Junggar Ocean still exists. In this study, we present geochronological, mineralogical, geochemical and isotopic data for basalts from the Chagantaolegai ophiolitic mélanges in Junggar. Zircon U-Pb dating on one basalt yielded a weighted mean 206Pb/238U age of 469 ± 7 Ma, which suggests that it formed in the Middle Ordovician. All rock samples belong to alkaline basalt and show similar geochemical characteristics, displaying high TiO2 (~3 wt%), (La/Yb)N (17.6–19.0), ΣREE (232–289 ppm) and enrichment in Nb and Ta, which implies an ocean island basalt (OIB) affinity. Based upon positive εNd(t) (+4.16 to +4.23), ΔNb (0.20–0.22) and low initial 87Sr/86Sr (0.70425 to 0.70452) and Zr/Nb (3.35–3.57), we suggest that the Chagantaolegai OIB samples were likely derived from a fertile mantle source related to plume. The OIB rock assemblage, chert and marble in the southern part of the Chagantaolegai ophiolitic mélange indicates that a Middle Ordovician seamount was accreted to the Boshchekul-Chingiz arc due to the northward subduction of the Junggar-Balkhash Ocean.

    • Cenozoic Crustally-derived Carbonate-rich Magmatic Rocks in West Junggar, North Xinjiang, Western China: Geochronology, Geochemistry and Tectonic Implications

      2021, 95(4):1112-1127. DOI: 10.1111/1755-6724.14772

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      Abstract:The carbonate-rich magmatic rocks of West Junggar are distributed in the Baijiantan and Darbut ophiolitic mélanges in the forms of extrusive rocks overlying the mélanges and dykes, either along the margins of the mélange or cross-cutting components of mélanges. Chilled margin and flow structures are present. A SHRIMP zircon U-Pb age of 39.7 ± 1.3 Ma indicates that these carbonate-rich rocks in West Junggar were formed during the Eocene. They have low concentrations in REEs, Th, U, Nb, Ta and are characterized by extremely low εNd(t), high (87Sr/86Sr)i ratios, relatively high δ18OV-SMOW values and high δ13CV-PDB values, which is similar with most sedimentary carbonates. Furthermore, no contemporaneous mantle-derived silicate rocks have yet been found in West Junggar. The carbonate-rich rocks in West Junggar are thus distinct from mantle-derived carbonatites and are interpreted to result from melting of the Carboniferous sedimentary carbonates at crustal levels, these rocks therefore being referred to as ‘crustal carbonatites’. The Eocene crustal carbonatites in West Junggar and other Cenozoic magmatic rocks in North Xinjiang are generally situated along regional strike-slip faults or fault intersections. Therefore, we propose that the reactivation of the Darbut and Baijiantan crustal-scale strike-slip fault zones (ophiolitic mélanges), due to the far-field effects of the Indian-Eurasian collision, enables decompression melting of the underlying continental lithospheric mantle. These resulting melts ascended to the lower crust through the strike-slip faults, causing partial melting of the Carboniferous carbonaceous sediments. The crustal carbonatites in West Junggar provide a new piece of evidence for Cenozoic magmatism in North Xinjiang and are also significant for the investigation of tectono-magmatic relations in North Xinjiang and the Central Asian Orogenic Belt.

    • Petrogenesis of Early Carboniferous Alkaline Basalt from the Wusun Mountain: Implications for Tectonic Evolution of the Western Yining Block, NW China

      2021, 95(4):1128-1138. DOI: 10.1111/1755-6724.14382

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      Abstract:Late Paleozoic volcanic rocks are well exposed in the Yining Block, NW China, and are predominately composed of andesites, rhyolites and volcaniclastics as well as minor basalts. Study of the petrology, whole-rock geochemistry and zircon U-Pb dating for the Early Carboniferous alkaline basalts from Wusun Mountain, western Yining Block, constrains their petrogenesis and tectonic evolution. The alkaline basalts consist mainly of plagioclases, mostly albite and labradorite, as well as clinopyroxenes and olivines; zircon U-Pb dating indicates their formation at ca. 350 Ma. Geochemically, the basaltic samples have low SiO2 contents, and high TiO2, Al2O3 and alkaline contents, coupled with high Na2O/K2O ratios, displaying an alkaline basalt affinity. They show remarkable LILE enrichment and HFSE depletion. Meantime, these samples have relatively high TFe2O3, MgO, and Mg# values as well as Ni and Cr, relatively high Sm/Yb and U/Th, suggesting origination from a mantle source metasomatized by slab fluids. They formed in a transitional tectonic setting from arc to intraplate, showing a typical affinity of back-arc basin basalts. The alkaline basalts were likely generated in a nascent back-arc extension setting resulting from slab rollback of the southern Tianshan oceanic lithosphere. A bi-directional subduction model seems more reasonable for the evolution of the southern Tianshan Ocean. These new data will provide a new tectonic model for Late Paleozoic tectonic evolution of the western Yining Block.

    • Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes

      2021, 95(4):1139-1157. DOI: 10.1111/1755-6724.14688

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      Abstract:Ophiolitic peridotites exposed in the Eastern Desert (ED) of Egypt record multiple stages of evolution, including different degrees of partial melting and melt extraction, serpentinization, carbonatization and metamorphism. The present study deals with metaperidotites at two selected localities in the central and southern ED, namely Wadi El-Nabá and Wadi Ghadir, respectively. They represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano-sedimentary succession that represents island–arc assemblages. The studied metaperidotites are serpentinized, with the development of talc-carbonate and quartz-carbonate rocks, especially along shear and fault planes. Fresh relics of primary minerals (olivine, orthopyroxene and Cr-spinel) are preserved in a few samples of partially-serpentinized peridotite. Most of the Cr-spinel crystals have fresh cores followed by outer zones of ferritchromite and Cr-magnetite, which indicates that melt extraction from the mantle protolith took place under oxidizing conditions. The protoliths of the studied metaperidotites were dominated by harzburgites, which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole-rock chemical compositions. The high Cr# (0.62–0.69; Av. 0.66) and low TiO2 (<0.3 wt%) contents of the fresh Cr-spinels, the higher Fo (89–92; Av. 91) and NiO (0.24–0.54 wt%, Av. 0.40) contents of the primary olivine relics, together with the high Mg# (0.91–0.93; Av. 91) and low CaO, Al2O3 and TiO2 of the orthopyroxene relics, are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone setting. The investigated peridotites have suffered subsequent phases of metasomatism, from ocean-floor hydrothermal alteration (serpentinization) to magmatic hydrothermal alteration. The enrichment of the studied samples in light rare earth elements (LREEs) relative to the heavy ones (HREEs) is attributed to most probably be due to the contamination of their mantle source with granitic source hydrothermal fluids after the obduction of the ophiolite assemblage onto the continental crust. The examined rocks represent mantle residue that experienced different degrees of partial melting (~10% to 25% for W. El-Nabá rocks and ~5% to 23% for W. Ghadir rocks). Variable degrees of partial melting among the two investigated areas suggest mantle heterogeneity beneath the Arabian-Nubian Shield (ANS).

    • Formation of Foliations and their Related Minerals from Diagenetic to Medium-grade Metamorphic Rocks: A Case Study of the Hongyanjing and Liao-Ji Backarc Basins, China

      2021, 95(4):1158-1170. DOI: 10.1111/1755-6724.14790

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      Abstract:Deciphering the relationship between polyphase tectonic foliations and their associated mineral assemblages is significant in understanding the process from diagenesis to low-/medium-/high-grade metamorphism. It can provide information related to strain, metamorphic conditions and overprinting relationships and so help reveal the tectonic evolution of orogenesis. In this study, we predominately focus on the formation of foliations and their related minerals, as developed in two separate basins. First of all, two stages of axial plane cleavages (S1 and S2) were recognized in the Hongyanjing inter-arc basin, the formation of the S1 axial plane cleavage is associated with mica rotation and elongation in mudstones in the local area. The pencil structure of S2 formed during the refolding phase, the minerals in the sedimentary rocks not changing their shape and orientation. Secondly, in the Liao-Ji backarc basin, foliations include diagenetic foliation (bedding parallel foliation), tectonic S1 foliation (secondary foliation or axial plane cleavage of S0 folding) and crenulation cleavage (S2). The formation mechanism of foliation changes from mineral rotation or elongation and mineral solution transfer in S1 to crystal-plastic deformation, dynamic recrystallization and micro-folding in S2. Many index metamorphic minerals formed from low-grade to medium-grade consist of biotites, garnets, staurolite and kyanite, constituting a typical Barrovian metamorphic belt. Accordingly, a new classification of foliation is presented in this study. The foliations can be divided into continuous and disjunctive foliations, based on the existence of microlithons, detectable with the aid of a microscope. Disjunctive foliation can be further sub-divided into spaced foliation and crenulation cleavage, according to whether (or not) crenulation (micro-folding) is present. The size of the mineral grains is also significant for classification of the foliations.

    • Zircon Trace Element Constraints on U-Pb Dating: A Case Study of the Huayuangong A-type Granite in the Lower Yangtze Region, Eastern China

      2021, 95(4):1171-1182. DOI: 10.1111/1755-6724.14736

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      Abstract:For magmatic rocks, it is often found that zircon 206Pb/238U and 207Pb/235U ratios continuously plot on the concordia line with a relatively large age span for the same sample, which gives rise to large dating errors or even unrealistic dating results. As the trace element concentrations of zircon can reflect its equilibrated magma characteristics, they can be used to determine whether all the analytical spots on the zircons selected to calculate the weighted mean age are cogenetic and formed in a single magma chamber. This work utilizes the results of zircon trace element concentrations and U-Pb isotopic analyses to explore the screening of reasonable U-Pb ages, which can be used to determine a more accurate intrusion crystallization age. The late Mesozoic Huayuangong granitic pluton complex, which is located in the Lower Yangtze region, eastern China, was selected for a case study. The Huayuangong pluton comprises the central intrusion and the marginal intrusion. Two samples from the marginal intrusion yielded consistent zircon weighted mean 206Pb/238U ages of 124.6 ± 2.0 Ma and 125.9 ± 1.6 Ma. These analytical spots also exhibit Zr/Hf and Th/U ratios concordant with the evolution of a single magma, from which the dated zircons crystallized. However, for the central intrusion, the analytical spots on zircons from two samples all show a continuous distribution on the concordia line with a relatively large age span. For each sample from the central intrusion, the zircon Zr/Hf ratios do not conform to a single magma evolutionary trend, but rather can be divided into two groups. We propose that zircon Zr/Hf ratios can provide a new constraint on U-Pb zircon dating and zircon Th/U ratios can also be used as a supplementary indicator to constrain zircon dating and determine the origins of the zircons and whether magma mixing has occurred. By screening zircon analytical spots using these two indicators, the two samples from the central intrusion of the Huayuangong pluton produce results of 122.8 ± 4.3 Ma and 122.9 ± 2.2 Ma, which are consistent with the field observations that the central intrusion is slightly younger than the marginal intrusion.

    • Petrogenesis, Geodynamics and Radioactivity of the Granitic Rocks of the Nugrus Weakness Zone, South Eastern Desert, Egypt

      2021, 95(4):1183-1198. DOI: 10.1111/1755-6724.14740

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      Abstract:The studied granitic bodies belong to the south Eastern Desert of Egypt. They extend in a NNW–SSE trend along the same strike of the Nugrus weakness zone by which they are structurally controlled. These rocks are composed of biotite and biotite-muscovite monzogranites to syenogranites. Geochemically, a higher abundance of Ba and Rb in biotite granites with a relatively low abundance in biotite-muscovite granites as well as the diversity of Th, U, Nb, Ta, Zr, and REE reflects their origin from different sources and geodynamic settings. The biotite granites are predominantly metaluminous to low peraluminous whereas the biotite-muscovite granites have a peraluminous nature. Potassium enrichment at the expense of calcium in these rocks reflects a derivation from crustal sources by partial melting in the presence of a volatile system. Radiometric investigation showed high abundances of U (up to 38 ppm) and Th (up to 26 ppm) in biotite-muscovite granites relative to biotite granites (up to 5 ppm U and 18 ppm Th). Radioactive anomalies furthermore have been recorded in parts of biotite-muscovite granites that were affected by the faults (up to 116 ppm eU and 97 ppm eTh). Consequently, biotite-muscovite granites form a potentially fertile source for uranium mineralization.

    • Geochemistry and Zircon U-Pb Dates of Felsic-Intermediate Members of the Late Cretaceous Yüksekova Arc Basin: Constraints on the Evolution of the Bitlis–Zagros Branch of Neotethys (Elazığ, E Turkey)

      2021, 95(4):1199-1216. DOI: 10.1111/1755-6724.14694

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      Abstract:During the Late Cretaceous in the Eastern Mediterranean, the northern branch of the southern Neotethys was closed by multiple northward subductions. Of these, the most northerly located subduction created the Baskil continental arc at around 82–84 Ma. The more southerly and intra-oceanic subduction, on the other hand, produced an arc-basin system, the Yüksekova Complex, as early as the late Cenomanian–early Turonian. The abundant and relatively well-studied basaltic rocks of this complex were intruded by dykes, sills and small stocks of felsic–intermediate rocks, not previously studied in detail. The intrusives collected from five different localities in the Elaz?? region of eastern Turkey are all subalkaline, with low Nb/Y values. Most of them have been chemically classified as rhyodacites/dacites, whereas a small number appear to be andesites. In normal mid-ocean-ridge basalt (N-MORB)-normalised plots, the intrusives are characterised by relative enrichments in Th and La over Nb, Zr, Hf, Ti and high field strength elements (HREEs), indicating their derivation from a subduction-modified source. While their relatively high, positive εNd(i) values (+6.4 and +7.2) might suggest a depleted mantle source for their ultimate origin, somewhat radiogenic Pb values indicate a sedimentary contribution to the source of the rocks. The overall geochemical characteristics indicate their generation in an oceanic arc setting.?The zircon U-Pb Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data obtained from five felsic-intermediate rock samples yielded intrusion dates of 80–88 Ma. This suggests that the Elaz?? oceanic arc-related intrusives are slightly younger than those of the Yüksekova arc-basin system, but coeval with the Baskil continental arc. However, the felsic–intermediate intrusives show different geochemical characteristics (oceanic arc-type, with a lack of crustal contamination) to those of the Baskil continental arc. This indicates that these two igneous systems are unrelated and likely developed in different tectonic settings. This, in turn, supports a geodynamic model in which the northern strand of the southern Neotethys was consumed by multiple northward subductions.

    • Geochemistry of Rhenium and Other Trace Elements in Molybdenite, Sar Cheshmeh Porphyry Cu-Mo Deposit, Iran

      2021, 95(4):1217-1235. DOI: 10.1111/1755-6724.14693

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      Abstract:LA-ICP-MS analysis of molybdenite?from the?Sar Cheshmeh porphyry Cu-Mo deposit (PCD), Iran, shows moderate concentration of Re (average?~207 ppm) and low concentration of chalcogenides?(average of?Pb + Te + Bi, ~31 ppm) as well as?metalloids?(average?of As + Sb + Ge,?~4.5 ppm).?The early-formed quartz–molybdenites associated with potassic alteration are characterized by moderately low concentration of Re (21–215 ppm with an average of 83 ppm), whereas the transitional quartz–molybdenite veins related to the sericitic stage of mineralization contain more Re?(62–465 ppm, with an average of 207 ppm).?In contrast, the late-formed quartz–molybdenite veins associated with phyllic alteration show the highest concentration of Re (up to 1273 ppm with an average of 395 ppm). Gradual?increase?in Re content of molybdenites deposited throughout the evolution of the porphyry system is probably related to elevated ?O2?and acidic conditions of the ore fluids governing the transitional and late stage of mineralization, when compared to the moderately low ?O2?and basic conditions of the ore fluids precipitating the low-Re molybdenites associated with potassic?alteration.?The mixed mantle/crustal source of the ore-related magma and its fractionated composition in Sar Cheshmeh are consistent with magmatic conditions for the formation of Mo-rich and Re-poor PCDs in the world.

    • Re-Os Isotopic Age of Molybdenite of the Jingren Deposit and its Mineralogical Significance of Magnetite, Pyrite and Chalcopyrite

      2021, 95(4):1236-1248. DOI: 10.1111/1755-6724.14718

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      Abstract:The Jingren deposit is part of the Qimantage metallogenic belt within the eastern Kunlun orogenic belt, the largest metallogenic belt in Qinghai Province, northwestern China. Exploration data show that the metal resources of the Jingren deposit are greater than 93000 t in a mining area of 76.15 km2, which indicates significant exploration potential in the near future. Three W–E-trending faults, F1-3, dominate the extension of the mineralization zone, which consists of chalcopyrite, pyrite, magnetite, galena, sphalerite, and molybdenite as well as bismuth-bearing minerals. The deposit contains a large amount of late Triassic intrusive rocks, however, previous research did not reach a consensus on the timing or the origin of the mineralization owing to a lack of geochronological data and poor exposure conditions. In the present study, Re-Os isotopic dating from six molybdenite samples collected from a borehole of the granodiorite in the Jingren deposit using negative thermal ionization mass spectrometry (NTIMS) showed 187Re and 187Os concentrations of 0.26–4.40 ppm and 1.03–16.46 ppb, respectively, with an initial 187Os/188Os value of 0.06 ± 0.19. This proves that the Jingren deposit has a metallogenic age of (225 ± 4) Ma and is the product of united mineralization of the Qimantage metallogenic belt and that the Jingren deposit might actually be an Indosinian metallogeny. In addition, the Re content of these samples, at 0.42 ppm to 7.00 ppm shows that the mineralization was derived mainly from a crustal source. Furthermore, electron probe microanalysis (EPMA) conducted on chalcopyrite obtained from 22 metallic mineral samples revealed (Fe + Cu)/S ratios of 1.801–1.947 with an average of 1.852, which is lower than the ideal value (1.875). Besides, the main ore body formed in a relatively higher temperature environment than the surrounding rocks in the Jingren deposit. These data indicate that the Jingren deposit formed in a metallogenic environment at lower temperature. Moreover, according to the TiO2-Al2O3-(MgO + MnO) and TiO2-Al2O3-MgO genetic classification diagram for magnetite, the Jingren deposit most likely belongs to the skarn family. In addition, the Co-Ni-As genetic classification diagram of the pyrite indicates sedimentary and skarn genetic characteristics.

    • Hydrothermal Zircon Geochronology in the Shangxu Gold Deposit and its Implication for the Early Cretaceous Orogenic Gold Mineralization in the Middle Bangonghu–Nujiang Suture Zone

      2021, 95(4):1249-1259. DOI: 10.1111/1755-6724.14679

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      Abstract:As a typical orogenic gold deposit in Tibet, Shangxu gold deposit is located at the Bangong Lake–Nujiang River Metallogenic Belt in the south of Qinghai–Tibet Plateau. In this paper, zircon U-Pb dating, trace elements and Hf isotopic analysis were performed on Au-bearing quartz veins in the Shangxu gold deposit. Zircons from Au-bearing quartz veins can be divided into three types: detrital, magmatic, and hydrothermal zircons. There are two age peaks in detrital zircons: ca. 1700 Ma and ca. 2400 Ma. There are two groups of concordant ages including 157 ± 4 Ma (MSWD = 0.69) and 120 ± 1 Ma (MSWD = 0.19) in magmatic zircons, in which εHf(t) value of ca. 120 Ma from the magmatic zircons range from +8.24 to +12.9. An age of 119 ± 2 Ma (MSWD = 0.42) was yielded from hydrothermal zircons, and their εHf(t) values vary between +15.7 and +16.4. According to sericite Ar-Ar age, this paper suggests that an age of 119 ± 2 Ma from hydrothermal zircons represent the formation age of the Shangxu gold Deposit, and its mineralization should be related to the collision between Lhasa Block and Qiangtang Block. The metallogenic age is basically the same as the diagenetic age of Mugagangri granite, and εHf(t) value of hydrothermal zircon is significantly higher than that of the contemporaneous magmatic zircon, which indicates that there is a genetic relationship between the gold mineralization and the deep crust-mantle magmatism.

    • Hydrocarbon Generation Characteristics of Source Rocks from Different Saline Environments in the Dongpu Depression, Bohai Bay Basin, China

      2021, 95(4):1260-1278. DOI: 10.1111/1755-6724.14744

      Abstract (1607) HTML (0) PDF 27.48 M (2648) Comment (0) Favorites

      Abstract:The Dongpu Depression is a secondary salt-bearing tectonic unit in the Bohai Bay Basin, eastern China. The depositional environment of this depression regarding its Paleogene strata is clearly different in plane, including the saltwater environment (SE) in the north, the freshwater environment (FE) in the south and the brackish water environment (BE) in the middle. The result of oil and gas exploration in the Dongpu Depression shows that more than 90% of the proven oil reserves are distributed in the northern saltwater environment. Previous studies indicate that the organic geochemistry characteristics and the hydrocarbon generation capacity of the source rocks are very clearly diverse under different environments, which results in the significant differences in the proved reserves between the north and the south. In order to further explore the differences in the hydrocarbon generation capacity of the source rocks under distinct depositional environments and the mechanism of their occurrence, three samples from different depositional environments (W18-5 for SE, H7-18 for BE, CH9 for FE) were used for confined gold tube pyrolysis experiments. The results show that the CH4 yields of W18-5, H7-18 and CH9 increase with increasing temperature, the maximum yields being 405.62 mg/g TOC, 388.56 mg/g TOC and 367.89 mg/g TOC, respectively. The liquid hydrocarbon yields of W18-5, H7-18 and CH9 firstly increase with increasing temperature and then decrease after the critical temperatures. The maximum yields of C6?14 are 149.54 mg/g TOC, 140.18 mg/g TOC and 116.94 mg/g TOC, the maximum yields of C14+ being 852.4 mg/g TOC, 652.6 mg/g TOC and 596.41mg/g TOC, respectively for W18-5, H7-18 and CH9. To summarize, the order of hydrocarbon potential from high to low is W18-5, H7-18 and CH9. On this basis, through analyzing the influencing factors of hydrocarbon differences, this paper reveals that the saltwater environment is characterized by 4 factors: higher salinity, halophilic algae, high paleo-productivity and a strongly reducing environment, which are beneficial to the enrichment of organic matter and lead to the formation of high levels of sapropelite and exinite. According to the variation of oil and gas components in the pyrolysis experiments, the hydrocarbon generation process is divided into three stages: kerogen cracking, oil cracking and C2?5 cracking. Combined with hydrocarbon generation characteristics and stages, the evolutionary model of hydrocarbon generation for source rocks under different environments is established.

    • Distribution of Mid-deeply Buried Sand-bodies and their Hydrocarbon Significance at Basin Margins: Case Study of the Paleogene in the Eastern Liuzan Area of the Nanpu Sag, Bohai Bay Basin, China

      2021, 95(4):1279-1294. DOI: 10.1111/1755-6724.14782

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      Abstract:The current research aims to unlock the temporal and spatial distribution of sand-bodies and their relationship with hydrocarbon accumulation in the mid-deep layer of basin margins, located in the eastern part of the Liuzan area of the Nanpu Sag, Bohai Bay Basin, China. Through this study, the main target interval of the area was divided into two fourth-order sequences. The lean sand mixed sedimentary belt with great importance in controlling hydrocarbon accumulation was identified through the comprehensive use of 3D seismic data, logging data, lithological data and seismic inversion data. A detailed analysis of sand-body development characteristics and their role in controlling hydrocarbon accumulation was conducted. The results reveal that the study area mainly develops two distinct fan-delta lobes from the NE-trending sediment supply direction. Due to the relatively high influence of the lacustrine transgression event, the scale of the lean sand mixed sedimentary belt within the SQ1-1 (the lacustrine transgressive systems tract) is relatively small, showing a relatively continuous distribution of sand bodies in the plane. Conversely, due to the relatively high impact of the lacustrine regression event, the scale of the lean sand mixed sedimentary belt developed within the SQ1-2 (the highstand systems tract) is relatively large, the two east sets of fan-delta sedimentary systems being clearly separated. The lean sand mixed sedimentary belt formed a good lateral occlusion belt in favor of hydrocarbon accumulation. Through composite analysis of structural interpretation results, sand-body distribution and well test data, it is evident that the lean sand mixed sedimentary belt located in the structural high is not a favorable zone for hydrocarbon accumulation. In contrast, the wing of the high part of the structure is the zone of sand-bearing bodies and is a favorable zone of hydrocarbon accumulation.

    • Geochemical Characteristics and Migration Pathways of Ordovician Carbonate Oil Reservoirs in the Tuoputai Area, Tarim Basin, Northwestern China

      2021, 95(4):1295-1309. DOI: 10.1111/1755-6724.14674

      Abstract (1385) HTML (0) PDF 11.13 M (2423) Comment (0) Favorites

      Abstract:Exploration potential is huge and the oil resources are rich in the Ordovician reservoirs of the Tarim Basin. However, the mechanism of hydrocarbon accumulation is complex and not yet fully understood. In the Tuoputai area, the hydrocarbon migration pathways and characteristics of deep hydrocarbon accumulation are revealed through analyses of the physical data of rich oil and gas, the geochemical parameters of oil, and fluid inclusions. The results show that the Ordovician oils in the Tuoputai area have the same geochemical characteristics as the mixed oil from the Lower Cambrian source rock and the Middle–Upper Ordovician source rock. The Ordovician reservoirs have been charged three times: in the late Caledonian, late Hercynian, and Himalayan stages. Oil charging occurred in the Hercynian stage, in particular, as it is the main filling period of hydrocarbon. The north-northeast (NNE)-trending TP12CX major fault, active in in these times and is dominant migration channel of hydrocarbon, but there is segmentation affected by the difference of activities. Oil maturity is higher in the south than in the north and is abnormally high near the major fault. Parameters related to migration indicate that oil migrated northeastward along the NNE-trending TP12CX major fault and adjusted laterally along the secondary faults and weathering crust, forming the present characteristics of oil and gas distribution.

    • Shale Gas Reservoir Evaluation by Geophysical Measurements: A Case Study of the Upper Ordovician–Lower Silurian in the Fenggang Block, Northern Guizhou Province

      2021, 95(4):1310-1321. DOI: 10.1111/1755-6724.14738

      Abstract (1345) HTML (0) PDF 26.18 M (2517) Comment (0) Favorites

      Abstract:With the aid of geophysical measurements, including seventeen two-dimensional (2D) seismic lines and the well logging curves of well FGY1, the structure and reservoir characteristics of the Upper Ordovician–Lower Silurian strata in the Fenggang block, northern Guizhou Province, were analyzed thoroughly to identify desert areas and favorable intervals. The results show that Longmaxi-Wufeng is the most prospect-rich formation, consisting of a thick succession of overmature black shale, this formation remaining partially in the Suiyang, Fenggang and Jianchaxi synclines. The Longmaxi-Wufeng shale, especially the lower member, was deposited in a reducing low-energy environment with relatively high U content and a low Th/U value. In this shale, the organic matter type (sapropelic and humic-sapropelic), total organic carbon (TOC) content, gas content, gas adsorption capacity, vitrinite reflectance and brittle mineral content are profitable for shale gas preservation and development. The fractures of this shale were closed because of its high overburden pressure. The gas adsorption capacity of this shale increases with increasing TOC content and Ro. In the Longmaxi-Wufeng Formation at well FGY1, the most favorable intervals are in the depth ranges of 2312.4–2325.1 m and 2325.8–2331.1 m.

    • Modeling of the Shale Volume in the Hendijan Oil Field Using Seismic Attributes and Artificial Neural Networks

      2021, 95(4):1322-1331. DOI: 10.1111/1755-6724.14739

      Abstract (1326) HTML (0) PDF 7.99 M (2252) Comment (0) Favorites

      Abstract:Petrophysical properties have played an important and definitive role in the study of oil and gas reservoirs, necessitating that diverse kinds of information are used to infer these properties. In this study, the seismic data related to the Hendijan oil field were utilised, along with the available logs of 7 wells of this field, in order to use the extracted relationships between seismic attributes and the values of the shale volume in the wells to estimate the shale volume in wells intervals. After the overall survey of data, a seismic line was selected and seismic inversion methods (model-based, band limited and sparse spike inversion) were applied to it. Amongst all of these techniques, the model-based method presented the better results. By using seismic attributes and artificial neural networks, the shale volume was then estimated using three types of neural networks, namely the probabilistic neural network (PNN), multi-layer feed-forward network (MLFN) and radial basic function network (RBFN).

    • Paleoearthquake Investigation along the Chenghai Fault Zone since ~500 ka, Southeast Margin of the Tibetan Plateau

      2021, 95(4):1332-1345. DOI: 10.1111/1755-6724.14513

      Abstract (1336) HTML (0) PDF 45.93 M (2697) Comment (0) Favorites

      Abstract:The Chenghai fault zone is located in the Sichuan–Yunnan rhombus block, which is surrounded by the Honghe River, Xianshuihe–Xiaojiang, and Jinsha River fault zones. As a mid-continental active fault, it is one of the most important seismogenic fractures in the southeast margin of the Tibetan Plateau. Geological seismic study is an important supplement to the historical seismic record; therefore, identification of paleoearthquake events in this region is of great significance to reveal the pattern and mechanism of earthquake development. In this study, detailed investigation has been carried out on the earthquake traces that formed in the Quaternary sediments in the Jinsha River section of the Chenghai fault zone, and samples for dating chronology testing were also collected. Many paleoearthquake traces were discovered in the field, including earthquake fissions, dammed lake sediments and landslides, earthquake-generated rock falls, seismic faults, and sand liquefaction veins. The collected samples were tested using optically stimulated luminescence, electron-spin resonance, and U-series methods. A total of 68 chronological samples were dated, combined with the results of field investigations, and 10 large paleoearthquake events were discovered in this region since 500 ka, which are at approximately 450, 400, 345, 300, 250, 190, 155, 105, 75, and 25 ka. Ten tectonic activity periods that produced multiple paleoearthquake events were identified since 500 ka. This study identifies paleoearthquake events in longer scales, larger spaces, and more extensive sediments, which provides new perspectives and new ideas for paleoearthquake research.

    • Coordinated Exploration Model and its Application to Coal and Coal-associated Deposits in Coal Basins of China

      2021, 95(4):1346-1356. DOI: 10.1111/1755-6724.14495

      Abstract (1326) HTML (0) PDF 2.55 M (2422) Comment (0) Favorites

      Abstract:China is a top world producer of coal resources with numerous coal-rich basins country-wide that also contain coalbed methane (CBM), an unconventional natural gas resource. Recent exploration of coal and CBM resources has also led to the discovery of rare, precious, and scattered metal minerals, including sandstone-type U and Ga–Ge–Li. High-grade and industrial-value deposits have been discovered in the Ordos, Junggar, and other basins across China during exploration for coal resources. Application of coordinated exploration theories and techniques in multiple energy and coal-associated ore deposits, such as coal and unconventional natural gas in coal, achieves efficient and practical exploration of natural resources. Based on the systematic study of accumulation and occurrence of coal and coal-associated mineral resources in coal basins, the basic idea of coordinated exploration for coal and coal-associated deposits is proposed, and multi-targets and multi-methods based on a coordinated exploration model of coal-associated deposits is developed. Coordinated exploration expands the main exploration objective from coal seams to coal-associated series, extending the exploration target from targeting coal only to coal-associated deposits. Entrance times for exploration are decreased to realize coordinated exploration for coal, unconventional natural gas and syngenetic/associated mineral resources in coal by implementing a ‘one-time approach’ ―one time in and out of a coal seam to minimize disturbance and time needed for extraction. According to the differences of geological background in China’s coal basins, four coordinated exploration model types, including co-exploration of coal and coal-associated unconventional natural gas, coal and solid minerals, coal and metal minerals, and coal with water resources are established. Other models discussed include a multi-target coordinated exploration model for the combination of coal, coal-associated gas, solid minerals, and metal minerals accordingly. The exploration techniques of coal and coal-associated resources include regional geological investigation and research and synthetic application of other techniques including seismic surveys, drilling, logging, and geochemical exploration. Particularly, applying the ‘multi-purpose drill hole’ or reworking coalfield drill holes into parameter wells, adding sample testing and logging wells, determining gas-bearing layers by logging and gas content measurement, jointly measuring multiple logging parameters, sampling, and testing of coal-strata help in the exploration and evaluation of coal resources, coal-associated unconventional natural gas resources, and coal-associated element minerals. Accordingly, a system of integrated Space–Air–Ground exploration techniques for coordinated exploration of coal and coal-associated minerals is established. This includes high-resolution, hyperspectral remote-sensing technique, high-precision geophysical exploration and fast, precise drilling, testing of experimental samples, as well as coordinated exploration and determination methods of multi-target factors, multi-exploration means, multi-parameter configuration and optimization, big data fusions and interpretation techniques. In recent years, the application of this integrated system has brought significant breakthroughs in coal exploration in Inner Mongolia, Xinjiang and other provinces, discovering several large, ten-billion-ton coalfields, such as the Eastern Junggar and Tuha basins, and also in exploration and development of CBM from low-rank coals in Fukang, Xinjiang, discovery the Daying U Deposit in Inner Mongolia, the Junggar Ultralarge Ga Deposit, Lincang, Yunnan, and the Wulantuga, Inner Mongolia, Ge-bearing coal deposits, and the Pingshuo Ultralarge Li–Ge Deposit.

    • Exploratory Data Analysis Applied in Mapping Multi-element Soil Geochemical Anomalies for Drill Target Definition: A Case Study from the Unpha Layered Non-magmatic Hydrothermal Pb-Zn Deposit, DPR Korea

      2021, 95(4):1357-1365. DOI: 10.1111/1755-6724.14404

      Abstract (1310) HTML (0) PDF 3.74 M (2220) Comment (0) Favorites

      Abstract:A factor analysis was applied to soil geochemical data to define anomalies related to buried Pb-Zn mineralization. A favorable main factor with a strong association of the elements Zn, Cu and Pb, related to mineralization, was selected for interpretation. The median + 2MAD (median absolute deviation) method of exploratory data analysis (EDA) and C-A (concentration-area) fractal modeling were then applied to the Mahalanobis distance, as defined by Zn, Cu and Pb from the factor analysis to set the thresholds for defining multi-element anomalies. As a result, the median + 2MAD method more successfully identified the Pb-Zn mineralization than the C-A fractal model. The soil anomaly identified by the median + 2MAD method on the Mahalanobis distances defined by three principal elements (Zn, Cu and Pb) rather than thirteen elements (Co, Zn, Cu, V, Mo, Ni, Cr, Mn, Pb, Ba, Sr, Zr and Ti) was the more favorable reflection of the ore body. The identified soil geochemical anomalies were compared with the in situ economic Pb-Zn ore bodies for validation. The results showed that the median + 2MAD approach is capable of mapping both strong and weak geochemical anomalies related to buried Pb-Zn mineralization, which is therefore useful at the reconnaissance drilling stage.

    • Reviews

      2021, 95(4):1365-1365.

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      Abstract:

    • Neoproterozoic Tectonic Events of Egypt

      2021, 95(4):1366-1405. DOI: 10.1111/1755-6724.14410

      Abstract (1340) HTML (0) PDF 60.67 M (2938) Comment (0) Favorites

      Abstract:The Egyptian Nubian Shield (ENS) represents the northwestern part of the Arabian-Nubian Shield and the northern extension of the East African Orogen. The ENS is regarded as being formed due to northward-directed escape tectonics. It is characterized by mild accretion and suture zones dominated by major strike-slip zones with a commonly sinistral sense of movement; some shear zones display a dextral sense of shear. It is dominated by gneisses and migmatites in the south, arc volcaniclastic metasediments and highly dismembered ophiolites in the central parts, whereas its northern part is dominated by late- to post-tectonic granitoids. In southern Sinai, the Neoproterozoic rocks are grouped into four complexes, namely Feiran–Solaf, Sa’al–Zaghra, Kid and Taba. The ENS ophiolites were formed between 730–750 Ma, mainly in a supra-subduction zone setting. The ENS has undergone a Neoproterozoic deformation history involving three successive phases: (1) Early N–S shortening phase (D1), (2) Syn-accretionary phase (D2) and (3) Post-accretionary phase (D3). The initial island-arc stage (780–730 Ma) is a N–S shortening phase initiated by collision between the Eastern Desert tectonic terrane to the north with both the Gebeit and Gabgaba terranes to the south (830–720 Ma). During the arc-splitting and back-arc spreading stage (730–620), voluminous syn-tectonic granitoids intruded into the ENS (750–610 Ma). The E–W-directed compressional/transpressional phase (620–450 Ma) led to the overall uplift of the central part of the ENS and consequently the development and exhumation of the core complexes in oblique convergent zones. The E–W intense shortening deformation resulted also in the formation of NW- and NE-striking sinistral and dextral strike-slip shear zones, respectively. The latest periods of the E–W-directed compressional/transpressional regime were characterized by deposition of the molasse-type Hammamat Sediments unconformably over the Dokhan Volcanics, or interbedded with them. The combined thrusting, folding and sinistral-reverse shearing structures have been interpreted to resulted from the E–W-directed compressional/transpressional phase in response to the oblique shortening of the Arabian-Nubian Shield between East and West Gondwana.

    • RESEARCH ADVANCES

      2021, 95(4):1405-1405.

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      Abstract:

    • First Report of Osteoglossiform Fish Huashia from the Cretaceous of Eastern Liaoning, China

      2021, 95(4):1406-1408. DOI: 10.1111/1755-6724.14786

      Abstract (1499) HTML (0) PDF 2.57 M (2426) Comment (0) Favorites

      Abstract:

    • First Record of Soft-shelled Turtle (Testudines, Trionychidae) from the Late Pleistocene of Heilongjiang, Northeast China

      2021, 95(4):1409-1410. DOI: 10.1111/1755-6724.14751

      Abstract (1446) HTML (0) PDF 1.46 M (2330) Comment (0) Favorites

      Abstract:

    • New Phenotypes of Limnocythere inopinata from Lakes in Badain Jaran Desert, Northern China

      2021, 95(4):1411-1412. DOI: 10.1111/1755-6724.14785

      Abstract (1420) HTML (0) PDF 1.07 M (2296) Comment (0) Favorites

      Abstract:

    • New Biological Records of Paleoecological Changes Inferred from Pollen Since 2500 cal. a B.P. in the Ebinur Lake Area, North Xinjiang

      2021, 95(4):1413-1414. DOI: 10.1111/1755-6724.14748

      Abstract (1340) HTML (0) PDF 1.56 M (2309) Comment (0) Favorites

      Abstract:

    • New Discovery of Ca. 38 Ma Ultramafic–mafic Dyke Swarms in the Mitizi Area, Northwestern Tibetan Plateau

      2021, 95(4):1415-1417. DOI: 10.1111/1755-6724.14745

      Abstract (1361) HTML (0) PDF 2.41 M (2334) Comment (0) Favorites

      Abstract:

    • New Discovery of ~1866 Ma High-temperature Mylonite in the Helanshan Complex: Marking a Late-stage Ductile Shearing in the Khondalite Belt, North China Craton

      2021, 95(4):1418-1419. DOI: 10.1111/1755-6724.14749

      Abstract (1383) HTML (0) PDF 1.82 M (2425) Comment (0) Favorites

      Abstract:

    • A Quantitative Method for Evaluating Fault Vertical Opening and Sealing Properties during Hydrocarbon-Charging Periods

      2021, 95(4):1420-1422. DOI: 10.1111/1755-6724.14787

      Abstract (1300) HTML (0) PDF 1.00 M (2393) Comment (0) Favorites

      Abstract:

    • 14C Chronology and Circulation of Potassium-rich Brine in Lop Nur Playa, Xinjiang, Northwestern China

      2021, 95(4):1423-1425. DOI: 10.1111/1755-6724.14750

      Abstract (1314) HTML (0) PDF 1.44 M (2269) Comment (0) Favorites

      Abstract:

    • Enrichment Patterns and New Discovery of Deep Lacustrine Shale Oil in the Upper Cretaceous Qingshankou Formation, Songliao Basin, NE China

      2021, 95(4):1426-1428. DOI: 10.1111/1755-6724.14746

      Abstract (1382) HTML (0) PDF 4.07 M (2363) Comment (0) Favorites

      Abstract:

    • The Enormous Potential of Gas Generation from Carboxylic Acid Salts

      2021, 95(4):1429-1430. DOI: 10.1111/1755-6724.14758

      Abstract (1347) HTML (0) PDF 1.03 M (2272) Comment (0) Favorites

      Abstract:

Chief Editor:HOU Zengqian

Governing Body:China Association for Science and Technology

Organizer:Geological Society of China

start publication :1922

ISSN:ISSN 1000-9515

CN:CN 11-2001/P

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