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The zircon-bearing Liushuzhuang Peridotite in the Tongbai Orogen provides insights into the composition and evolution of Paleozoic sub-arc lithospheric mantle between the North China and Yangtze cratons. This orogenic peridotite is dominated by clinopyroxene-free spinel facies harzburgite to dunite. The refractory nature is indicated by high olivine Mg# (up to 92.4), elevated spinel Cr# (74–87), and low orthopyroxene Al2O3 (mostly < 1.0 wt.%). The occurrence of zircon, amphibole, phlogopite, apatite, and LREE-enriched orthopyroxene, with Raman probe analyses showing amphibole and phlogopite inclusions in zircon, testifies to extensive fluid-driven metasomatism of the mantle at ca. 420 Ma (U–Pb zircon). The high spinel TiO2 contents (0.4–1.4 wt.%), the Cl-enriched apatite, and the hydrous secondary phases indicate that the metasomatic agent was volatile- (CO2 + H2O) and TiO2-rich. The elevated oxygen fugacity (∆logfO2 (FMQ) > 2.5) coupled with high spinel Cr# of peridotites suggest that they formed within highly oxidizing supra-subduction zone environment. In-situ87Sr/86Sri amphibole and apatite data indicate that the metasomatic fluids were slightly to moderately radiogenic (0.7032–0.7090) and therefore likely partially derived from the subducted Shangdan oceanic crust that separated the North China and Yangtze cratons. The very low 176Lu/177Hf (mostly < 0.0002) of metasomatic zircon and similar εHf(t) to Tongbai Orogen arc-related magmas implies that zircon grew during modification of sub-arc mantle. Juxtaposition with the host gneisses occurred after 410 Ma and before U–Pb closure during apatite cooling at ~ 340 Ma. The Liushuzhuang Peridotite therefore records intense metasomatism of the Paleozoic sub-arc mantle wedge prior to collision of the North China and Yangtze cratons. [ABSTRACT FROM AUTHOR]

A remarkable characteristic of the Bandar Abbas Hinterland is the frequent presence of oil seepages that can serve as an indicator of probable oilfields in the region. The Seeps A and B are located in the main Zagros Suture Zone, 150 km to the northeast of Bandar Abbas and 30 km to the west of the same city, respectively. The presence of well-known Paleozoic source rocks (e.g., Seyahou, Sarchahan, and Gurpi formations) in the vicinity of the mentioned oil seepages shows that the seeping oil is coming from an oil source. The present research is aimed investigating the petroleum system and determining the source of the mentioned oil seepages. Results of the Rock-Eval analyses showed that the samples of the Seyahou Formation are thermally overmatured, making them exhibit inadequate oil generation potential. These samples contain Type-III kerogen and were found to be in the metagenesis stage. However, compared to other formations, Sarchahan and Gurpi exhibited good hydrocarbon generation potentials. On the other hand, based on the PI - Tmax diagram, the Sarchahan Formation was found to be in the early oil and condensate production window (i.e., catagenesis stage) while the Gurpi Formation was seen to be immature. Biomarker analysis results showed that the samples were deposited in a mixed marine environment and contained Type-II and Type II/III kerogen. The reason behind the occurrence of the oil seepages in an oxidative environment could be the sever impact of the biological degradation. The stable carbon isotope composition of the crude samples supported the biomarker data in general. Therefore, it can be concluded that the studied oil seepages were probably sourced from the Sarchahan Formation. [ABSTRACT FROM AUTHOR]

The formation and evolution of the ancient continental crust are crucial issues in solid-earth geology which are commonly associated with global tectonic events and the formation of economically valuable magmatic-hydrothermal ore deposits. The Cathaysia Block, one of the ancient continents in Southeast Asia, can be subdivided into two parts: the West Cathaysia Block and the East Cathaysia Block. Unlike the East Cathaysia Block, no Precambrian rocks are exposed in the West Cathaysia Block, constraining further understanding of the formation and evolution of this block. In this study, a total of four hundred and thirty-three zircon U-Pb dating analyses and two hundred and eighteen Lu-Hf isotopic analyses on zircon grains from the Jurassic Dengfuxian granites and Ordovician Tanghu granites, Nanling Range, were carried out. LA-ICP-MS zircon U-Pb dating yields mean average 206Pb/238U ages of 152.6 ± 2.2 Ma (MSWD = 1.6) and 442.4 ± 1.7 Ma (MSWD = 3.8), which are regarded as the rock-forming age for the Jurassic Dengfuxian granites and Ordovician Tanghu granites, respectively. The 207Pb/206Pb ages of the inherited zircons from the Jurassic Dengfuxian granites and Ordovician Tanghu granites range from 522 Ma to 3395 Ma, hosting two major peaks at the 0.9–1.0 Ga and 2.4–2.5 Ga. In contrast to the East Cathaysia Block, the West Cathaysia Block lacks the age peak of 1.8–1.9 Ga, indicating that the West Cathaysia Block was not influenced by the assembly of the Columbia supercontinent in the Paleo-Proterozoic. In combination with the Lu-Hf isotopes, we proposed that the crust evolution of the West Cathaysia Block in Archean is dominated by juvenile crustal growth events, and dominated by the crustal reworking since the Proterozoic. The long duration of crustal reworking in the West Cathaysia Block resulted in the enrichment of lithophile elements (e.g., W, Sn, Nb, and Ta) in the crust of that region. Therefore, the Jurassic granites in the Nanling Range, which are mainly derived from the partial melting of Proterozoic basement rocks, became associated with large-scale tungsten polymetallic mineralization. [ABSTRACT FROM AUTHOR]

Copper mineralization in the Lower Paleozoic sedimentary cover of the Anti-Atlas (Morocco) is continually being revised not only to improve its mining capacity, but also to determine its origin, which remains a matter of debate. As evidenced by the various models proposed, the related research is fragmented, localized, and confusing. The origin of the Anti-Atlas Lower Paleozoic copper mineralization is shared between synergistic and epigenetic processes or a superposition of the two processes. Based on new tectono-magmatic data and a reinterpretation of the ore structural arrangement, we propose a link between the last concentration of copper deposits and the Late Triassic–Early Liassic CAMP (Central Atlantic Magmatic Province) tectono-thermal event, as evidenced by the significant concentration of copper mineralization in the three NE–SW corridors affected by extensional faults, some of which are filled with dolerite CAMP magma. The heat flow generated by the mafic dykes within these reactivated corridors causes mineralized fluids to up well into the sedimentary layers, depositing material rich in juvenile or leached copper, or even a mixture of the two. In some cases, these fluids are trapped by fracture systems that accompany passive folds initiated on normal faults. In other cases, these fluids can infiltrate bedding planes, and even karst caves, formed during carbonate exhumation. Notably, extensive NE–SW faults systematically cover the early Hercynian structures, suggesting that they belong to a post-Hercynian extensional episode. During the Late Triassic, the global fragmentation of the Pangaea supercontinent was manifested by the stretching of the continental crust at the margin of northwest Africa, with the simultaneous opening of the Central Atlantic Ocean and emplacement of CAMP magmatism. This last and often overlooked tectonothermal event must be considered in the remobilization and reconcentration of copper mineralization and other mineralization in Morocco. [ABSTRACT FROM AUTHOR]

In this study, twenty-six core shale samples were collected from the marine Lower Paleozoic shale in a well in the northeastern margin of the Yangtze Platform. Analyses of TOC content, mineral composition, major elements, along with trace and rare earth elements were conducted on the samples. The results were used to investigate the depositional conditions and their effects on organic matter accumulation and preservation. Generally, the sedimentation period of Niutitang Formation shale was in a cold and arid climate with anoxic marine environments, while the shale from Wufeng-Longmaxi Formation was formed in a warm and humid climate with oxic marine environments. In addition, the Wufeng-Longmaxi and Niutitang formations are characterized by low paleo-productivity. The organic matter enrichment for shale in this study could be simultaneously controlled by paleo-redox state and paleo-productivity. Organic matter enrichment of the Niutitang shale is mainly driven by preservation rather than productivity, while the dominant driving factor is the opposite for the Wufeng-Longmaxi shale. Additionally, palaeoclimate and terrestrial influx intensity were found to significantly impact the organic matter enrichment in the Wufeng-Longmaxi shale. The findings have implications for the understanding of the sedimentary processes, organic matter enrichment and preservation and shale gas potential of the study area. [ABSTRACT FROM AUTHOR]

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The giant gold deposit Muruntau in most works belongs to the "orogenic type". However, in the description of the geology of the deposit, there is usually no information about the stages (deformation, metamorphism) and the role of regional processes in the formation of host and mineralized rocks of the deposit. Our fieldwork provides unique geological evidence and previously unpublished data that are not reported in any other publications to date. This article presents the results of a detailed structural study of the terrane hosting the Muruntau gold deposit on the example of four sites and the results of deep drilling of two wells. The conducted studies confirm that the lowest Muruntau megaterrane consists of multi-stage metamorphosed Neoproterozoic–Early Paleozoic sedimentary-volcanic rocks and Late Paleozoic carbonate sediments overlain by Late Carboniferous flysch and olistostrome in the top. Two main stages (D1 and D2) of rock deformation in the lower part of the megaterrane associated with the Early Paleozoic accretion and two subsequent stages (D3 and D4) associated with the Late Paleozoic accretion and orogeny are described. Thrust processes D2 and D3 caused the formation of recumbent folds of different orientation and vergence. The normal antiform (D4) extending W–E is an orogenic fold. The Muruntau gold deposit is located in a regional synmetamorphic thrust zone called the Main Muruntau Thrust (MMT), which formed during the Early Paleozoic D2 stage. The MMT is responsible for the formation of secondary rock anisotropy along the cleavage of the D2 recumbent folds and conformal lens-like body of mineralized rocks and gently sloping veins with an area of 7.0 × 2.6 km. The internal structure of the deposit retains fragments of deformed gold quartz veins into recumbent folds. These structural data make it possible to link low-grade gold mineralized zones with Early Paleozoic deformations. We suggest that rock anisotropy within the MMT controlled mineralization twice: in the Early Paleozoic as a synmetamorphic flat high-permeable zone and in the Late Paleozoic as a relatively low-permeable zone for post-magmatic fluids. [ABSTRACT FROM AUTHOR]

[Display omitted] • 432 Ma granites formed in a syn-collisional setting. • 422-411 Ma granites formed in a post-collisional environment. • East Kunlun evolved into a post-collisional stage in the Early Devonian. Middle Paleozoic granitoids in the East Kunlun Orogen of the northern Tibetan Plateau play an important role in deciphering the tectonic evolution of the Proto-Tethys Ocean. This paper presents petrological, whole-rock geochemical, zircon U-Pb geochronological, and Sr-Nd isotopic data for granodiorites, garnet-bearing granites, and syenogranites in the East Kunlun Orogen. These granites have zircon U-Pb ages of 432 Ma, 423 Ma, and 413 Ma, respectively, taken to be their crystallization ages. They have mineralogical and geochemical features of I- (or I-S transition), S-, and A-type granitoids, respectively. Primitive magma of the I-type granodiorite is inferred to be derived from partial melting of a juvenile lower crust, whereas the S-type garnet-bearing granites could be linked to partial melting of greywackes in the middle/lower crust. In contrast, the A-type syenogranite may have been derived from the Neoproterozoic granites at high-temperature and low-pressure conditions. In addition, the 432 Ma I-type granites were likely emplaced in a syn -collisional setting, and the 423–411 Ma S- and A-type granites formed in a post-collisional environment in response to the slab break-off/detachment and asthenosphere upwelling during the Middle Silurian-Early Devonian. These distinct granites suggest that the East Kunlun Orogen evolved into a syn -collisional stage due to the collision between North Kunlun and South Kunlun Terrane during the Middle Silurian (ca. 438 Ma) before experiencing a post-collisional collapse in the Late Silurian to Early-Middle Devonian. These results together with the Silurian orogeny of regional Qilian and Qinling orogens suggest the Proto-Tethys oceans in central China fully closed during Middle Silurian-Early Devonian, and then generated the middle Paleozoic Kunlun-Qilian-Qinling Orogen in East Asia. [ABSTRACT FROM AUTHOR]

The time frame and detailed tectonic processes during the transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean regimes have long been controversial. The Jiamusi Block, which is located in the eastern margin of the Eurasia, is a transitional zone between the Paleo-Asian Ocean and the Paleo-Pacific Ocean regimes. The Jiamusi Block has been considered to be the last unit collaged to the Central Asian Orogenic Belt (CAOB) but also influenced by subsequent westward subduction and accretion of the Paleo-Pacific plate. Abundant geological units in the Jiamusi Block provide key insights into the final amalgamation of the CAOB and the onset of the Paleo-Pacific Ocean regime. This paper presents a review on the tectonic affinity and origin linkage of the Jiamusi Block based on detailed characterization of both the granulite facies basement and the Phanerozoic sedimentary cover, as well as the surrounding Mesozoic accretionary complexes. From these analyses, we develop an integral tectonic model for the Jiamusi Block aiming to better constraining the evolution history from the final amalgamation of the eastern CAOB to the onset of the Paleo-Pacific Ocean regime. We found that the tectonic history of the Jiamusi Block can be divided into at least four stages: (1) prior to the Early Paleozoic, the Jiamusi Block was conterminous with the other mirco-continents in NE China as a large combined block, which originated from the Sayang–Baikal orogenic belt within the Siberia Craton and experienced the Pan-African metamorphism (ca. 500 Ma); (2) along the tectonic evolution of the CAOB, those blocks in NE China drifted south to the eastern CAOB in some time after ca. 500 Ma; (3) during the Late Paleozoic, the subduction of the Mongol-Okhotsk Ocean or the Panthalassa induced back-arc extension and eventually the opening of the Heilongjiang Ocean, which ripped off the Jiamusi Block and drove it eastward away from the CAOB; (4) during the period from the Late Triassic to the Early Jurassic, following the closure of the Heilongjiang Ocean and the subduction of the Paleo-Pacific Ocean in the east, the Jiamusi Block was reunited with the contiguous CAOB, marking the final amalgamation of the CAOB and tectonic shift to a dominance by the Paleo-Pacific Ocean tectonic regime in the region. • Jiamusi Block is a hinge of tectonic transition between the Paleo-Asian Ocean and the Paleo-Pacific Ocean regimes. • Jiamusi Block together with the other parts of NE China was more likely originated from the Sayang–Baikal orogenic belt. • Jiamusi Block experienced eastward rift away during the Early Permian and reunion to the CAOB during the Late Triassic. [ABSTRACT FROM AUTHOR]

The presence and evolution of a late Paleozoic mountain chain with a paleogeographic disposition similar to the present-day Andean Cordillera is analyzed in this paper. This mountain range, here named Ancestral Andes, was formed during the Gondwanan orogeny (Permian) and separated the Paleopacific Sea from the eastern retroarc basins in this part of South America. Three basement types are involved in the roots of the Ancestral Andes: 1. poorly exposed Mesoproterozoic-Neoproterozoic high-grade metamorphic rocks probably remains of the Chi-Cu terrane, 2. Cambrian-Silurian sedimentary and metamorphic rocks formed during the Famatinian orogeny, and 3. Neoproterozoic to early Carboniferous sedimentary and metamorphic rocks originated during the Chanic orogenic cycle. According to tectonic activity, sedimentary facies, and magmatic record, the Gondwanan cycle comprises seven tectosedimentary stages: 1) Late Mississippian-Early Pennsylvanian (post-Chanic orogeny marine sedimentation), 2) late Early Pennsylvanian (sea-level fall and progradation of sandy wedges in an extensional pre-orogenic period), 3) Middle-Late Pennsylvanian (sea level fluctuations at the end of the pre-orogenic phase), 4) latest Pennsylvanian-early Cisuralian (active tectonism during the beginning of the uplift of the Ancestral Andes, 5) middle Cisuralian (continental and shallow marine sedimentation during the main phase of the Ancestral Andes uplift), 6) late Cisuralian-Guadalupian (continental sedimentation and beginning of the post-orogenic volcanism), 7) late Guadalupian-Lopingian (most active post-orogenic volcanism). The stages 1, 2, and 3 correspond to the pre-orogenic phase of the Gondwanan cycle recorded in the Agua Negra Formation, which is mainly marine with thin continental intercalations. Stages 4 and 5 represent the orogenic conditions that promoted the uplift of the Ancestral Andes and a sudden change from mainly marine (Agua Negra Formation) to continental (San Ignacio Formation) facies. Finally, stages 6 and 7 show the intense magmatic activity developed during the Guadalupian-Lopingian and probably early Triassic times (Choiyoi Group, anaorogenic conditions). The late Paleozoic paleofloras recovered from different stratigraphic intervals into the Ancestral Andes allow establishing that stages 1, and 2, bear remains of the Nothorhacopteris-Botrychiopsis-Ginkgophyllum (NBG) Biozone (latest Mississippian-Early Pennsylvanian). Stage 3 yielded Late Pennsylvanian plant remains and invertebrates while the Stage 5 provided silicified trunks of Cuyoxylon (San Ignacio Formation) and palynofloras characterized by Lueckisporites (La Puerta Formation) of Cisuralian age. • A mountain chain, the Ancestral Andes, was formed during the Gondwanan orogeny. • Ancestral Andes separated the Paleopacific Sea from the eastern retroarc basins. • The Gondwanan cycle (Ancestral Andes) is divided into seven tectosedimentary stages. • The uplift of the Ancestral Andes had a crucial effect in the retroarc basins. • The Atacama phase produced the onset of the uplift of the Ancestral Andes. [ABSTRACT FROM AUTHOR]

The Paleozoic volcano-sedimentary rocks within the structural basement of the horst-and-graben system of the Catalan Coastal Ranges (CCR) are composed of black shale, volcaniclastic sediments, lava flows, sills and lithocrystalloclastic tuffs. Paleozoic sediments are depleted in high-field strength elements (HFSE) such as Nb, Ta, Zr, Hf and Ti, suggesting their accumulation within the Andean-type active continental margin environment. Volcanic rocks within the Paleozoic CCR sequence belong to shoshonitic and high-K volcanic series and are enriched in Cs, Rb and Ba and depleted in HFSE, which is consistent with their derivation from metasomatized (possibly through deep recycling of pelagic sediments) subduction-related mantle source. The presence of sills (sill-sediment complex) suggests that Paleozoic basement of the CCR was formed within the rifted active continental margin or an arc-back-arc basin system akin to the modern Western Pacific subduction configuration. This complex volcanic terroir hosts world-class wines of the Priorat DOQ region. The presence of framboidal pyrite and magnetite, siderite, sphalerite xenotime, (La–Ce–Nd)-monazite, zircon and baddeleyite, as well as cuprite, tenorite and cupriferous and native silver in volcanic-derived black shale (and consequently in the world-famous "llicorella" soil overlying it) may have had dramatic effects on wine quality and sensory characteristics. These mineral features, together with strong enrichment of Priorat shale in Au, Ag and, to a lesser extent, Pt could have pronounced effects on (1) rates and specific types of chemical reactions; (2) plant metabolism; (3) response to nutrient components and (4) determination of grape flavor. Volcanic wine terroirs, such as the Priorat DOQ region, are special geologic environments for wine growth, capable of producing unique wine aromatic and gustatory characteristics. [ABSTRACT FROM AUTHOR]

The southern Sanandaj-Sirjan Zone (SSZ) forms the core of the Zagros orogen and consists of a stack of four major tectonic units, all of which were thrust southwestward over the Neyriz ophiolites. Precambrian and early Paleozoic rocks were affected by high-grade metamorphism, whilst the late Paleozoic (Carboniferous and Permian) and Mesozoic rocks are of low grade to unmetamorphosed. Geothermobarometric results indicate that the investigated area experienced peak temperature–pressure conditions of ~ 650 °C and 8–9 kbar, before being partly overprinted by greenschist facies conditions. We identified two main deformational phases (D2, D3) and some relics of an older one (D1) in the southern SSZ. D1 is inferred based on local evidence of tight D2 folds that fold a pre-existing schistosity (S1), associated with prograde- and peak metamorphism. D2 shows large-scale, tight-to isoclinal F2 folds and a penetrative S2 foliation, forming the dominant foliation in our study area. The P–T path is clockwise and associated with a geothermal gradient of ~ 20 °C/km, suggesting a collision-related geodynamic setting, preceding D2, and possibly linked to an early stage of D1. D3 is characterized by open folds (F3) and thrusts developed after greenschist facies metamorphism. Based on the metamorphic grade and stratigraphic age of folded units, D2 is inferred to be Eo-Cimmerian, and D3 post-Cretaceous, coeval to the Zagros orogeny. Concerning the oldest phase (D1), for which only circumstantial structural evidence exists, we discuss whether its age is pre-Cimmerian, possibly Variscan, or Eo-Cimmerian as suggested in previous literature. This study uses metamorphic assemblages and structures of the southern SSZ, to retrace its geodynamic evolution, which started with burial associated with high-temperature metamorphism, followed by Eo-Cimmerian shortening, and finally terminated with additional shortening related to the Zagros collisional event. [ABSTRACT FROM AUTHOR]

The North Qaidam subduction-collision zone is a typical Alpine-type ultra-high pressure (UHP) metamorphic zone due to the Early Palaeozoic subduction of the Qaidam Block beneath the Oulongbuluke Block, with an integrated record of oceanic subduction, continental subduction, collision, and exhumation to post-collisional extensional collapse. In this study, systemic petrology, zircon U-Pb geochronology, Hf isotopic data and whole-rock geochemical analyses have been carried out for granitoids in the North Qaidam UHP metamorphic units to determine their petrogenesis and further reveal the tectonic evolution of the continental collision orogen. Zircon U-Pb dating yields weighted mean ages of 433 ± 2 Ma, 351 ± 8 Ma, 416 ± 4 Ma, 389 ± 3 Ma and 383 ± 1 Ma, with the εHf(t) values of the latter three ages ranging from −2.4 to 3.3, −5.9 to 1.1 and −3.3 to 2.4, respectively. Based on field relationship, petrological, geochronological, and geochemical results, these granitoids could be divided three groups. The early group granodiorites (~433 Ma) show a marked chemical resemblance to adakites: (1) high La/Yb and Sr/Y ratios, with low Y and HREE values; (2) high Al2O3 and low Mg#, Cr, and Ni values with obvious positive Eu anomalies. Petrological and geochemical characters indicate that the early group adaktic granodiorites may be derived from partial melting of metabasite in a thickened mafic lower crust. The middle group granites (~416 Ma) have an affinity to I-type granitoids, characterized by high Na2O contents (>4.18 wt.%) and low A/CNK values, which were probably generated by partial melting of felsic gneiss of subducted continental crust. The late group granites (389 ~ 351 Ma) are also I-type granitoids, which were originated from partial melting of Mesoproterozoic crust, with minor mantle material input. According to a comprehensive study of these granitoids, along with regional geological background and HP-UHP metamorphism, a four-stage evolutionary process of the North Qaidam UHP metamorphic belt from oceanic subduction, continental subduction, collision to extensional collapse is proposed. After the final closure of the Proto-Tethys Ocean, the subducted continental crust experienced HP-UHP eclogite-faces metamorphism (460 ~ 430 Ma), and thickening of the lower crust lead to generation of adakites and S-type granites. Following break-off of the subducting oceanic slab (425 ~ 400 Ma), the reduction in negative buoyancy caused the exhumation of deeply subducted continental crust accompanied by associated anataxis and syn-collisional I-type granitoids, representing the transition in tectonic regime from compression to extension. Due to the tectonic transition, mantle-derived intrusions and post-collisional granitoids were emplaced during 400 ~ 350 Ma. Simultaneously, the pronounced decreasing in La/Yb and Sr/Y ratios of magmatic rocks (age of 460 ~ 350 Ma) suggested that the crustal thickness decreased gradually from syn-collisional to post-collisional stage. [ABSTRACT FROM AUTHOR]

The platycerate gastropods Orthonychia yutaroi Ebbestad, sp. nov. (Ordovician, Boda Limestone, Sweden), O. enorme (Silurian, Sweden, Gotland), O. parva (Pennsylvanian, Finis Shale Member, USA), and Orthonychia sp. (Mississippian, Imo Formation, USA) are studied including their protoconch morphology. Orthonychia yutaroi is the oldest known species in Orthonychia. Platycerates contain species with both, openly and tightly coiled protoconchs. This is the first report that tightly coiled protoconchs occur in Orthonychia. This and previously published observations blur the diagnostic difference between orders Cyrtoneritimorpha (openly coiled protoconch) and Cycloneritimorpha (tightly coiled protoconch). We suggest to treat Cyrtoneritimorpha and Cycloneritimorpha as synonyms of Neritimorpha. The monotypic Devonian genus Pragoserpulina is morphological so close to the Orthonychia species reported herein that synonymy of both genera seems to be possible (and thus of the families Pragoserpulinidae and Orthonychiidae). Protoconch morphology and dimensions suggest that the studied platycerate species had planktotrophic larval development. By contrast, two studied Carboniferous euomphaloid species (one with an openly and the other with tightly coiled protoconch) have paucispiral, large protoconchs indicating non-planktotrophic larval development. We assume that openly and tightly coiled protoconchs were present in various Paleozoic gastropod clades and that selection acted against the openly coiled protoconch morphology. It has previously been proposed that increasing predation pressure in the plankton was the reason for the demise of openly coiled protoconchs (Paleozoic plankton revolution). The presence of larval planktotrophy in platycerates excludes the possibility that they belong to extant basal gastropod clades such as Patellogastropoda, Cocculiniformia, and Vetigastropoda. However, a previously proposed close relationship to Neritimorpha is corroborated. [ABSTRACT FROM AUTHOR]

The mechanism of Caledonian orogeny in South China is still controversial. The main argument focuses on the issue that whether there existed oceanic subduction. To answer this question, the complex Puyang pluton in the central part of Wuyi orogenic belt was selected for zircon U–Pb dating, in‐situ Lu–Hf isotopic analysis and geochemical testing. The Puyang pluton is mainly composed of granodiorite and diorite. The results of geochronology indicate that the granodiorite and diorite emplaced at 450 ± 3.9 Ma and 443 ± 4.0 Ma. Their emplacement time were well corresponding to the subduction stage of the Yunkai orogeny in the southwestern part of Cathaysia block during the Early Paleozoic (460–440 Ma). The Puyang adakite‐like granodiorite shows enrichments in Sr, but depletions in Y and Yb contents, high in Na2O, K2O and Al2O3, with εHf(t) values range from −10.5 to −7.4 (mean of −9.0) and two‐stage Hf model ages range from 1.91 to 2.10 Ga. These characteristics indicate that the magmas were generated by partial melting of subducted oceanic crust mixed with melts from the above wedgy mantle peridotite. The Puyang high‐Mg diorite shows enrichments in Sr and Ba, depletions in Rb, Y and Yb contents, and strongly high in MgO and Al2O3 contents, with εHf(t) values of −2.9 to 0 (mean of −1.4) and two‐stage Hf model ages of 1.43 to 1.61 Ga. These indicate that the magmas were mainly generated by partial melting of the wedgy mantle peridotite, mixed by adakitic melts from subducted oceanic slab. Comprehensive analysis shows that Puyang adakite‐like granodiorite and high‐Mg diorite were formed in fore‐arc setting, where the mantle and crustal magmas mixed during the oceanic subduction initiation period. By extension, this study offered important evidences to support the point that the Caledonian orogeny in South China was related to oceanic subduction which initiated prior to ~450 Ma. [ABSTRACT FROM AUTHOR]

The Aqishan-Yamansu belt in Eastern Tianshan (NW China) hosts several important Fe and Fe-Cu deposits, the origin of which is the subject of considerable debate. The coexistence of various types of ore-forming fluids makes it difficult to distinguish the genesis of the Fe-Cu deposits. We present detailed textural and compositional data on magnetite from the Paleozoic Shuanglong Fe-Cu deposit to constrain the formation of iron oxides and the evolution of the ore-forming fluids and thus define the genesis of the Fe-Cu ores. Based on the mineral assemblages and crosscutting relationships of veins, two mineralization stages were established, including the early Fe mineralization and late Cu mineralization stage. Three types of magnetite, i.e., platy (MA), massive (MB), and granular (MC) magnetite occur in the Fe mineralization. Backscattered electron (BSE) images identified display oscillatory zoning in an early hematite and transformational mushketovite phase (MA-I), characterized by abundant porosity and inclusions, as well as two later generations, including an early dark (MA-II, MB-I, and MC-I) and later light magnetite (MA-III, MB-II, and MC-II). The MA-I has extremely high W contents and mostly displays as micro-and invisible scheelite inclusions, which were probably caused by the W expulsion during mushketovitization. The texture and composition of magnetite suggest that the later light magnetite formed via dissolution and reprecipitation of the precursor dark magnetite, and the temperature and oxygen fugacity of fluids decreased over time. Our study also shows the MB-II magnetite and coexisting chlorite display synchronous oscillatory zoning, with the calculated temperature from 444 to 212 °C. Such variations could indicate the incursion of external low-temperature fluids with high salinity, which can dissolve the primary dark magnetite. This study provides a good example of using magnetite to trace the complex evolution and multiple sources of ore-forming fluids. [ABSTRACT FROM AUTHOR]

The Lower Carboniferous is represented in southwestern Virginia and northeastern Tennessee as a narrow band of mostly marine sedimentary rocks approximately 135 km long and represents a series of transgressive and regressive sea-level episodes. Only one vertebrate has been recorded from these strata (a now lost specimen of "Cladodus" collected from Hancock County, east Tennessee in the mid-Twentieth Century) prior to the current report. Saivodus striatus (Chondrichthyes, Ctenacanthiformes) is herein described for the first time from the state of Virginia, more than 350 km from its closest known occurrence. These chondrichthyans are some of the latest records of marine vertebrates from the Rheic Ocean during its closure in advance of the Alleghenian Orogeny and subsequent uplift of Paleozoic strata in the southern Appalachians. [ABSTRACT FROM AUTHOR]

The Late Paleozoic is an important epoch of coal-bed accumulation in the North China, particularly in its western segment, where a world-class coal field has been found and exploited for three decades. Coal-bearing layers recorded rapid Late Carboniferous to Early Permian sea-level rise that led to the evolution of the shallow marine tidal flat basin, followed by regression that resulted in the formation of deltaic facies. However, little attention has been paid to the tectonic factors that assisted in the coal accumulation processes, which have been demonstrated worldwide to be pivotal. In this study, we evaluate the significant influence of southward subduction of the middle segment of the Paleo-Asian Ocean (PAO) during Carboniferous to Early Permian deposition of coal-bearing neritic to deltaic successions in the western North China Block (NCB). We pinpoint a direct link between basin-filling evolution of the northwestern Ordos Basin and the progressive uplift of the Inner Mongolia continental arc triggered by the south-dipping subduction of the Solonker ocean plate. Sedimentary facies variation and paleocurrent reconstruction indicate sedimentary routing from the north to northeast. The petrology and detrital zircon geochronology of sampled sandstones indicate evolving provenances from a dominated cratonic basement to a mixed orogen and continental arc. The Carboniferous samples are generally quartz arenites and contain a large number of Archean to Paleoproterozoic zircons with small amounts of Paleozoic arc pluton components, indicating sediment supply dominated by the western NCB Precambrian basement. In contrast, the youngest sample of the Shanxi Formation is sub-litharenite, the age spectrum of which is characterized by the dominance of ca. 450 and 270 Ma ages, indicative of a high influx of Paleozoic arc detritus. This shift in sandstone petrology, detrital zircon distribution, and depositional setting allows us to link the shoaling of the Ordos Basin with mountain building and the unroofing of the continental arc, which enhances our understanding of both the subduction of the PAO and coal accumulation in the NCB. [ABSTRACT FROM AUTHOR]

The Bogda Range (hereafter referred to as the Bogda) is located in the Eastern Tianshan. Interpreting its tectono-thermal history is critical to understanding the intra-continental evolution of the Tianshan. In this study, we report new apatite fission track data from the late Paleozoic–Mesozoic sedimentary rocks in the northern Bogda and the Late Paleozoic granites in the southern Bogda to investigate the exhumation history of the Bogda. Apatite fission track ages dominantly range from the Jurassic to earliest Cenozoic (~143–61 Ma), except for one siliciclastic sample from the Early Permian strata with an older age of ~251 Ma. Thermal history modeling, together with detrital apatite fission track age peaks, reveal that the Bogda underwent three episodes of cooling during the Late Triassic, the Late Cretaceous, and the Late Miocene. The Late Triassic rapid cooling may represent the initial building of the Bogda, which is probably related to the final closure of the Paleo-Asian Ocean. During the Late Cretaceous, the Bogda may have experienced a moderate exhumation, which was possibly triggered by the extensive tectonic extension in the central–eastern Asian regime during the Cretaceous. The Late Miocene rapid cooling may be a response to the rapid uplift of the whole Tianshan, due to the far-field effect of the continuous India–Eurasia collision since the beginning of the Cenozoic. [ABSTRACT FROM AUTHOR]

Eclogites in the Acatlán Complex, southern Mexico, record the subduction history of the complex. Previous studies indicate that the proto-Acatlán Complex reached < 50 km depth during subduction. Yet, a recent study reported higher pressures for a single eclogite, questioning the maximum depth reached by the complex during subduction. In this work, I re-calculate eclogite pressure and temperature (P–T) conditions using thermobarometric methods applicable to eclogite-facies mafic rocks to a set of eclogites cropping out throughout the high-pressure belt of the Acatlán Complex—the Piaxtla Suite. I find that Acatlán eclogites record substantially—and systematically—greater pressures than previously reported. Calculations show that eclogites from the central part of the Piaxtla Suite (in the Piaxtla area) record consistent pressures of ~ 2.0 GPa and temperatures ranging between 460 and 675 °C. Eclogites from the northern part of the Piaxtla Suite (Mimilulco and Santa Cruz Organal areas) lack phengite, thus pressures were not calculated; temperatures calculated for these rocks at a fixed pressure (2.0 GPa) yield contrasting temperatures (511 °C and 870 °C, respectively). Mimilulco eclogite likely records similar pressures (~ 2.0 GPa) to other Piaxtla eclogites, whereas the pressures of Santa Cruz Organal eclogites might have been different, and likely experiencing a different thermal history compared to the rest of the eclogites from the Piaxtla Suite. Overall, these results indicate that the Acatlán Complex subducted to greater depths than previously thought implying a faster burial—exhumation cycle of the proto-Acatlán Complex. [ABSTRACT FROM AUTHOR]

The results of biostratigraphic studies of the Devonian–Lower Carboniferous deposits of the Bambuysko–Olingda Subzone of the Vitimkan–Tsipa Zone of the Baikal–Vitim fold system are presented. These deposits are isolated from the composition of the Riphean and Vendian–Cambrian formations. Their age was revised on the basis of numerous findings of fossil fauna and flora. The Bambuiskaya carbonate and Chulegminskaya terrigenous suites and the Kadala terrigenous-carbonate stratum are assigned to the Devonian. The Uendect volcanogenic-terrigenous sequence is dated as Late Devonian (Famennian)–Early Carboniferous (Tournaisian), while the terrigenous Ognenskaya and Amatkan suites are dated as Early Carboniferous (Tournaisian and Visean), respectively. Significant changes have been made to the Paleozoic stratigraphic scheme of the subzone. Paleolandscape reconstructions for the Bambuysko–Olingda basin and coastal land areas in the Devonian–Early Carboniferous are proposed. The Devonian carbonate complex was formed under calm conditions of a shallow warm shelf sea. A change in the paleolandscape environment occurred at the Devonian–Carboniferous boundary. The accumulation of thick strata continued under the conditions of a deepening open shelf-slope paleobasin adjacent to the volcanic zone. [ABSTRACT FROM AUTHOR]

The lack of preserved basement results in uncertain placements of many terranes in Southeast Asia. Here, we flag the first evidence of the oldest basement in Indonesian Borneo, which can help locate terranes in Borneo on the northern margin of Gondwana in the early Paleozoic and explain the regional tectonic setting of the island. Two schist samples from the Embuoi Complex in the Semitau Block, Northwest Kalimantan yielded zircon U‐Pb dates of 453.3 ± 1.9 Ma and 462.4 ± 2.6 Ma, respectively, representing the formation time of the protolith. Petrographic, internal structural and high Th/U ratios of zircons indicate that the protolith of schists is of magmatic origin. The zircons have εHf(t) values of –4.1 to +1.1 and Hf model ages of 1.37–1.69 Ga, indicating they were derived from a mixed source of juvenile crust with old components. By comparison of zircon age distribution, two‐stage Hf model ages and εHf(t) variations of the early Paleozoic igneous rocks from Semitau with those of South China, Tengchong–Baoshan, and Indochina, the Semitau Block was most likely a part of or placed next to the Indochina Block of northern Gondwana during the early Paleozoic. Such a similar tectono‐magmatic pattern on northern Gondwana formed a prolonged early Paleozoic arc‐related belt associated with subduction of the Proto‐Tethyan Ocean. [ABSTRACT FROM AUTHOR]

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A new collection of papers spanning the breadth of the Arctic provides new insight into the region's geodynamic evolution. New results pertain to lithospheric structure, the link between magmatic and extension-related tectonic processes, variations in the composition and velocity structure of the lower crust in the Amerasia Basin, and provenance and paleogeography of Paleozoic to Triassic successions across the Arctic. Elucidation of geodynamic processes in the Eurasia Basin suggests new hypotheses for future research in the complex and poorly understood Amerasia Basin. New results from detrital zircon provenance studies as well as from stratigraphic facies compilations constrain the Late Paleozoic to Triassic paleogeography of the Arctic realm. [ABSTRACT FROM AUTHOR]

In their comment, Smith et al. (2016) discount the astronomical cycle identifications made from Middle Permian cyclostratigraphy in our recent paper (Fang et al. 2015), declaring that we presented defective null models and improper hypothesis tests, and greatly overestimated the statistical significance of cycles. Here we respond in detail to clarify the decisions that were made in our work, and to correct errors and omissions and other misunderstandings arising in their comment. We also discuss the advent of objective methodologies that promise to improve research in cyclostratigraphy in the near future. [ABSTRACT FROM AUTHOR]

Research on tight gas enrichment in coal measure strata is contentious worldwide. Gas logging anomalies are very common in the upper Paleozoic coal-bearing strata in the Southern Qinshui Basin of eastern China. The distribution characteristics of these free gases are closely related to the degree of fracture development. The rock pore aspect ratio ( α ) can reflect the morphology of rock pores and fractures. In this paper, we use full wave logging data to propose a new logging assessment method for tight clastic rock reservoir fractures via the extraction of effective pore aspect ratios. The basic concept is as follows: (1) we extract the rock matrix mineral modulus and dry rock modulus of the rocks using an optimized algorithm, and (2) we invert the effective pore aspect ratio of coal measure strata using the theoretical model of a differential equivalent medium. The research results show that the studied clastic rocks in coal measure strata are very tight, with porosity levels that are generally less than 5%, and sections in which fractures have formed often correspond to relatively low α values of less than 0.1. The microfracture-bearing sections identified based on α inversions correspond well to the sections with fractures at the core scale. Thus, this method can be used to identify fractured sections at the core scale. For sandy mudstone, microfractures mainly exist in sandy intervals, and α is negatively related to rock porosity and positively related to shale content. Regardless of lithology, i.e., sandstone, mudstone or coal, the communication and transport capacity of fracture systems are greater than those of the pore system, and coal-derived gas reservoirs form when there are good gas sources, transportation systems, fracture systems and preservation conditions. Similar to the formation mechanism of fractures in rocks, α is also derived from mechanical mechanisms, and this study shows that the inversion process is effective in characterizing the degree of fracture development in tight clastic rocks in coal measure strata based on elastic rock properties. [ABSTRACT FROM AUTHOR]

This paper presents new zircon U–Pb, Hf isotope, and whole-rock major and trace element data for early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China, in order to constrain the early Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt (CAOB). Zircon U–Pb dating indicates that early Paleozoic magmatic events within the northern Songnen–Zhangguangcai Range Massif (SZM) can be subdivided into four stages: Middle Cambrian (~ 505 Ma), Late Cambrian (~ 490 Ma), Early–Middle Ordovician (~ 470 Ma), and Late Ordovician (460–450 Ma). The Middle Cambrian monzogranites are K-rich, weakly to strongly peraluminous, and characterized by pronounced heavy rare earth element (HREE) depletions, high Sr/Y ratios, low Y concentrations, low primary zircon ε Hf (t) values (− 6.79 to − 1.09), and ancient two-stage model (T DM2 ) ages (1901–1534 Ma). These results indicate derivation from partial melting of thickened ancient crustal materials that formed during the amalgamation of the northern SZM and the northern Jiamusi Massif (JM). The Late Cambrian monzonite, quartz monzonite, and monzogranite units are chemically similar to A-type granites, and contain zircons with ε Hf (t) values of − 2.59 to + 1.78 and T DM2 ages of 1625–1348 Ma. We infer that these rocks formed from primary magmas generated by partial melting of Mesoproterozoic accreted lower crustal materials in a post-collisional extensional environment. The Early–Middle Ordovician quartz monzodiorite, quartz monzonite, monzogranite, and rhyolite units are calc-alkaline, relatively enriched in light REEs (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), depleted in HREEs and high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), and contain zircons with ε Hf (t) values of − 7.33 to + 4.98, indicative of formation in an active continental margin setting. The Late Ordovician alkali-feldspar granite and rhyolite units have A-type granite affinities that suggest they formed in an extensional environment. A comparison of early Paleozoic magmatic events and Hf isotopic model ages between the northern SZM and the JM indicates that these two massifs have similar histories of Mesoproterozoic and early Paleozoic crustal accretion and reworking, although the SZM contains much older crustal materials than the JM. [ABSTRACT FROM AUTHOR]

In the southernmost part of the Parana Basin, records of the late Paleozoic glaciation occur in a discontinuous form preserved in paleovalley systems excavated in the crystalline basement. This paper addresses one of these paleovalleys, the Mariana Pimentel, which extends over 60 km with NW-SE valley direction and a constant width of 2.5 km. With the objective of demonstrating that the paleovalley worked as a fjord during the glaciation period, its origin as well as sedimentary fill and morphology were analyzed. The paleovalley morphology was obtained through electrical resistivity (electrical sounding and lateral mapping) and mathematical modeling in four transverse sections. The morphology of the paleovalley documented by the U-shape, steady width, and high depth reaching up to 400 m are typical features of modern glacial valleys. The sedimentary facies that fill the base of the paleovalley, such as rhythmites and dropstones with thickness up to 70 m and diamictites with faceted pebbles (up to 5 m thick) are signs of its glacial origin. During the glaciation period, the paleovalley had a connection to the epicontinental sea located to the northwest, extended toward Namibia, and was excavated by glaciers from the highlands of this region. Thus, the evidence attests that the Mariana Pimentel paleovalley was a fjord during the late Paleozoic glaciation. The duration of the late Paleozoic glaciation (which is longer than the Quaternary glaciation), the apatite fission track that suggests erosion up to 4 km thick in the study area, and the lack of preserved hanging valleys in the Mariana Pimentel indicate that the paleovalley once featured a higher dimension. Furthermore, the existence of paleofjords excavated in the border of the basement corroborates the idea of small ice centers controlled by topography during the late Paleozoic glaciation. [ABSTRACT FROM AUTHOR]

The ophiolites that occur as inliers among the Late Paleozoic formations in the Middle Gobi area are crucial for understanding the tectonic evolution of South Mongolia. In this paper, we conducted detailed studies on the Namdain hundy ophiolite to provide some constraints on the Early Paleozoic evolution of the Middle Gobi region in Mongolia. The ophiolite mainly consists of ultramafic rocks (carbonatation), plagiogranite, metagabbro, basalt and chert. The metagabbro and plagiogranite from Namdain hundy ophiolite yielded SHRIMP zircon U-Pb ages of 528 ± 7 Ma and 519 ± 5 Ma, respectively. Though most of the volcanic rocks of this ophiolite show supra-subduction zone (SSZ) affinity, samples with OIB and N-MORB geochemical features were also identified, indicating genesis in a forearc setting. The granodiorite intruding into the Namdain hundy ophiolite yielded a SHRIMP zircon U-Pb age of 491 ± 3 Ma, which constrained the upper age limit of ophiolite emplacement. This granodiorite shows adakitic geochemical affinity, attesting to the existence of Cambrian paleo - subduction in South Mongolia. Based on the available data so far, we suggest the Middle Gobi area comprises of the Manlay accretion complex, the island arc and the Biluutiin ovoo back-arc basin. The spatial configuration of these three tectonic belts suggests that the polarity of the paleo-ocean subduction was from south to north in the Early Paleozoic, forming a trench-arc-basin system south of the Central Mongolia microcontinent. [ABSTRACT FROM AUTHOR]

This paper presents the results of U–Pb dating of detrital zircons from six metasedimentary rocks in the Taowan and Kuanping groups in the northern margin of the North Qinling Orogenic Belt (NQB), Central China, for constraining the tectonic affinity of the NQB, the existence time and tectonic features of the Kuanping Ocean and the accurate northern boundary of the NQB. Zircon U–Pb dating indicates that the protoliths of the two metasedimentary rocks from the upper and lower parts of the Taowan Group were deposited later than ∼1111 and ∼871 Ma respectively. However, the protoliths of the four metasedimentary rocks from different layers of the Kuanping Group were deposited later than ∼781, ∼668, ∼515 and ∼477 Ma, respectively, suggesting that the Taowan Group and the Kuanping Group both have an abnormal or non-Smithian stratigraphic sequence. The age populations and predominant peak ages of detrital zircon grains from the Mesoproterozoic–middle Neoproterozoic metasedimentary rocks in the Taowan and Kuanping groups indicate that their provenances were mainly attributed to the NQB and subordinately from the Yangtze Craton (YZC), suggesting that the two groups both belong to the NQB and the northern boundary of the NQB should be placed to the north of the Taowan Group, which can be called the Paleo-Luonan–Luanchuan Fault. However, the Nd–Pb whole-rock isotopes, zircon Hf isotopes and trace element compositions of the Precambrian basement rocks and the Neoproterozoic granitic magmatic events in the NQB are significantly different from those in the YZC, suggesting that the NQB was more likely to be an independent microcontinent adjacent to the YZC from the Mesoproterozoic to the Neoproterozoic, and experienced a unique geological history. On the other hand, together with the record of the oldest MORB-type basalt with an age of 1445 Ma in the Kuanping Group, the first late Mesoproterozoic sedimentary record (∼1111 Ma) in the Taowan Group, to be reported using precise geochronological data in this study, it indicates that the Kuanping Ocean separated the NQB from the NCC that had already existed to the north of the NQB before the Mesoproterozoic, and was a major ocean basin which had lasted for a long time, rather than as a back-arc basin. [ABSTRACT FROM AUTHOR]

The Paleozoic tectonic framework of the eastern Hexi Corridor Belt is ambiguous. However, thick Paleozoic sediments from the eastern Hexi Corridor Belt can provide clues to this problem. In this paper, we deal with the detrital zircon provenance of Middle Ordovician to Late Devonian strata using LA-ICP-MS U–Pb dating, documenting the temporal and spatial changes of provenance. Detrital zircon U–Pb ages indicate that the primary provenance was the Qilian Orogenic Belt and the Alxa Block. However, two samples from Late Devonian strata show different provenance characteristics, from the North Qilian Orogenic Belt, and the Alxa Block and the North China Block, respectively. Different age distributions through time reflect provenance changes due to continuous convergence of the Central Qilian Block and the Alxa Block from the Middle Ordovician to Late Devonian. A significant age cluster ranging from 2000 to 1800 Ma, which is a detrital zircon signature of the North China Block, appeared in the Late Devonian Zhongning Formation. Our preferred interpretation is that the amalgamation of the Alxa Block and the North China Block likely occurred at that time. Moreover, similar Paleozoic fossils, paleolatitudes and detrital zircon distribution indicate that the Hexi Corridor Belt has an affinity to eastern Gondwana. [ABSTRACT FROM AUTHOR]

In this paper, we utilize large igneous intrusions as a key to a detailed analysis and understanding of the late Paleozoic evolution of the Ringkøbing-Fyn High, an important structural element in the North West European Craton. The study takes advantage of high-quality 3D seismic data and boreholes to map the geometry and lateral distribution of intrusive sills cross-cutting the sedimentary strata at a low angle (transgressive sills). Our analysis shows that the transgressive sills most likely sourced the vast extrusion of volcanics, which covered most of the Early Permian Northern Basin and which is associated to the Skagerak-Centered Large Igneous Province (SCLIP). Furthermore, a geometrical analysis of the sills demonstrates that the magmatic source for the sills was located SE of the studied area, suggesting a correlation with geophysically inferred lower crust intrusions. Hence, we are in this study able to constrain the full magmatic system from the lower crust intrusions to the surface volcanics. Intrusion of the sills occurred prior to an Early Permian faulting event, which created rotated fault blocks outlining the present Ringkøbing-Fyn High. The sills exposed for erosion at the crest of the footwall in turn controlled the Late Permian paleo-topography and the distribution of the Zechstein evaporites due to the fact that they are harder to erode. Hence, we are able to demonstrate a topography controlled thickness variation of the Zechstein evaporites. The study furthermore emphasizes that an understanding of the deepest parts of the North Sea Basin is crucial when evaluating the potential for yet unrecognized hydrocarbon plays. [ABSTRACT FROM AUTHOR]

Terrestrialization probably began more than one billion years ago and irreversibly altered biogeochemical processes at planetary scale. In this paper, we focus on the terrestrialization process of the Streptophyta, the division that includes charophytes and land plants (embryophytes) and whose members are today ecologically dominant in all terrestrial environments. The timing and the phylogenetic context of the early evolution of land plants are reviewed. The available information on the relationships within embryophytes and related organisms is compiled in two informal consensus trees based either on morphological/anatomical or on molecular data. We also consider the algal/embryophyte transition through the analysis of the evidence provided by microfossils (cryptospores and spores). The ongoing debate about the definition of the term cryptospores, but more importantly about the biological affinities of these microfossils that are possibly derived from early land plants, is discussed. All important clades of embryophytes, with a focus on their Palaeozoic representatives, are described; the significance of several embryophyte key characters is evaluated. The terrestrialization of land plants evolved in different steps. The new term “proembryophytic phase” is introduced to define the very long period of time during which the green algae ancestor of land plants acquired all the evolutionary characters that ultimately allowed their terrestrialization since the late Precambrian. An “eoembryophytic phase”, spanning the Middle-Upper Ordovician, is defined based on the occurrence of the earliest evidence of liverwort-like plants. The inception of the trilete spores in Late Ordovician times is then taken to define the start of the eo/eutracheophytic phase, which lasts until the first occurrence of vascular plant macrofossils in the Silurian. [ABSTRACT FROM AUTHOR]

The Lower Silurian Qusaiba Hot Shales (QHS) are proven source rocks for oil within the Paleozoic, and possibly some of the Mesozoic, reservoirs in Saudi Arabia. Moreover, these shales have oil shale potential where they are immature and shallow enough for mining, as well as unconventional shale oil and shale gas potential, in areas where they are within oil-maturity and gas-maturity levels, respectively. The QHS were deposited in relatively shallow marine environments under anoxic water conditions, resulting in accumulation of amorphous kerogen, organic-walled graptolites and acritarchs. Across the Arabian Basin, organic matter quality does not show much variation for the QHS, but the maturity varies greatly as a result of varying burial history. Thermal maturity assessment of shale source rocks that lack vitrinite, such as the Qusaiba Hot shales, continues to be challenging, especially where conflicting measurements are obtained from different sources. This paper presents an integrated assessment of QHS thermal maturity parameters, based on cores from 13 carefully selected boreholes that – based on regional basin models – are believed to cover a wide maturity range (ca. 0.5 to 2.0% Ro). We conducted some analyses on kerogen (maceral petrography, graptolite reflectance, UV-fluorescence, whole rock pyrolysis, Raman spectroscopy of graptolite) and other analyses on bitumen extracts (GC and GC–MS of saturate and aromatic fractions, and FTIR spectroscopy of the asphaltene fraction). We show that using many thermal maturity parameters reduces uncertainty significantly, and we therefore recommend that graptolite reflectance analyses should be conducted in support of other maturity indicators. Proper reflectivity measurements of the graptolites set the reference for comparison of other maturity parameters obtained from petrographic, geochemical, and spectroscopic techniques. Our work provides a template by which Qusaiba thermal maturity can be more accurately estimated when only a limited set of maturity parameters is available. [ABSTRACT FROM AUTHOR]

Detailed qualitative and quantitative studies using the X-ray computed microtomography proved to be a reliable source of information about the pore space properties of clastic and carbonate reservoir rocks. X-ray computed tomography with higher resolution (nano) allows improving and completion of porous rocks analysis in aspects of new parameters determination. In this paper, results of the X-ray computed microtomography analysis were presented for core samples probed from the Palaeozoic carbonate intervals (Modryn formation) from the selected wells located in the Central-Eastern Poland. Several parameters were calculated on the basis of microtomographic images (total porosity, tortuosity, homogeneity parameter, mean chord length, Euler number), which allowed to parameterize pore space structure of tight carbonates. In the case of rock hydrocarbon potential determination, e.g. filtration properties, computed X-ray microtomography turned out as an alternative method in rock characterization. It appeared that the Modryn formation consists of rocks with poorly developed pore space with limited filtration abilities. [ABSTRACT FROM AUTHOR]

Metasedimentary rocks of the Pyeongan Supergroup, which occur as roof pendants on the northeastern margin of the Yeongnam massif, South Korea, preserve a record of the impact of the Late Permian–Triassic Songrim (Indosinian) orogeny in the eastern Eurasia margin. Metamorphic results of this paper have revealed that the metasedimentary rocks were affected by three metamorphic events during the Middle Permian to Middle Mesozoic. Representative mineral assemblages from three metamorphic zones I, II and III are Cld + And ± Ky ± St, Grt + St + Ky + Bt ± And, and And + Sill + Bt ± Grt ± St, respectively. Kyanite and sillimanite paramorphs after andalusite occur in zones I and III, respectively. Metamorphic P–T conditions and paths were determined from conventional geothermobarometers and compositional isopleths of chloritoid, staurolite, and garnet on P–T pseudosections in the MnO–Na 2 O–CaO–K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O (MnNCKFMASH) and KFMASH–T (TiO 2 )–O (Fe 2 O 3 ) systems. In the study area, the Pyeongan Supergroup experienced medium pressure regional metamorphism (M1 and M2) belonging to greenschist to amphibolite facies followed by thermal metamorphism (M3). The M1 metamorphism occurred at 450–500 °C and 2–4 kbar and produced the kyanite paramorph after andalusite. The M2 metamorphism occurred at 520–600 °C and 4–6 kbar, and was associated with the growth of garnet, staurolite, and kyanite. The later thermal metamorphism occurred at ca. 580 °C and ca. 4 kbar, and was caused by intrusion of Jurassic granitoids. The medium pressure regional metamorphism (M1 and M2) have occurred around 270 Ma during the Songrim orogeny based on the SHRIMP U–Pb zircon ages. [ABSTRACT FROM AUTHOR]

Once situated between the Central Tianshan and Junggar terranes during Paleozoic time, the Junggar Ocean was a major southern branch of the Paleo-Asian Ocean. Thus, when and how it was closed are essential in understanding the final assembly of the Central Asian Orogenic Belt. However, the exact closure time of the Junggar Ocean remains unresolved due to the lack of reliable timing of collision-related regional metamorphism. This paper reports whole-rock geochemical and zircon U–Pb and Lu–Hf isotopic data for granitic gneisses from the northern margin of the Central Tianshan block, which can provide crucial constraints on the final closure of the Junggar Ocean. Mineral assemblages and geochemical suggest that the protoliths of the Central Tianshan gneisses are weakly peraluminous high-K calc-alkaline I-type granites, possessing typical subduction-related features such as strong enrichment in LREE and LILE and depletion in HFSE. Negative Eu anomalies (δEu = 0.46–0.81) and highly variable zircon Hf isotope compositions indicate various amounts of residual plagioclase in the source and crustal contamination during magma formation. LA-ICPMS U–Pb dating on magmatic-type zircons (72%), characterized by euhedral to subhedral shapes, concentric oscillatory zoning, high Th/U ratios (0.30–2.05) and large ranges of ε Hf (t) values (− 3.4 to + 8.7; up to 6 epsilon units in each sample), yields consistent weighted mean 206 Pb/ 238 U ages of ca. 325–320 Ma, interpreted as the crystallization ages of the granitic protoliths. Geochemical signatures and dominantly positive zircon ε Hf (t) values reveal that the protoliths were emplaced in a continental arc setting, pinpointing the development of a late Early to early Late Carboniferous continental arc system on the northern margin of the Central Tianshan block, probably related to the southward subduction of the Junggar oceanic plate. Meanwhile, younger ages at ca. 303–301 Ma were obtained on recrystallized zircon-rims and unzoned/homogeneous zircons (25%) with narrow ranges of ε Hf (t) values (− 1.8 to + 7.2; < 3 epsilon units in each sample), considered as the timing of a later tectonothermal event, which was associated with strong deformation that formed the gneissosity of the granitic gneisses. Combined with previous studies, we suggest that this event most likely resulted from the arc–continent collision/accretion between the island arcs (e.g. Bogda, Dananhu) in the Junggar Ocean and the Central Tianshan block during the final closure of the Junggar Ocean, which led to the final assembly of the Eastern Tianshan during the latest Carboniferous time. [ABSTRACT FROM AUTHOR]

Abstract The paper "Enrichment of Bi-Be-Mo-Cd-Pb-Nb-Ga, REEs and Y in the Permian coals of the Huainan Coalfield, Anhui, China" by Munir et al. (2018) provides new data on the geochemical compositions of the late Paleozoic coals from five different mines in the Huainan Coalfield, China, as well as proximate analyses, vitrinite reflectance measurements, maceral contents, and mineralogical constituents. A critical examination, however, suggests that a large proportion of the reported data are questionable, and also that references cited at a number of points are either improper or incomplete. [ABSTRACT FROM AUTHOR]

The noble gases He and Ar are trace components in natural gas. Although their genesis is significantly different from that of hydrocarbon gases, they can provide key information on the accumulation and preservation of natural gas. In this paper, the relative and absolute abundances of He and Ar in lower Paleozoic shale gas samples from different areas of southern China were systematically analyzed, and the relationships between the concentrations of noble gases and the accumulation and expulsion of shale gas were evaluated. The evolution of He and Ar concentrations in shale gas system can be divided into three phases: the early accumulation stage, the hydrocarbon dilution stage and the preservation and enrichment stage. The generation of a large amounts of methane in the shale leads to the lowest relative concentrations of He and Ar in the hydrocarbon dilution stage. After that, the tectonic uplift causes the partial loss of the shale gas, and methane is no longer generated, but He and Ar are still produced. The concentrations of He and Ar present in shale gas are mainly controlled by the conditions of the preservation and enrichment stage. Tectonic uplift is the main reason for the loss of shale gas, and later uplift often results in higher gas content, which also leads to relatively low concentrations of He and Ar. The absolute abundance of residual Ar atm and the He/Ar ratio of a shale gas can indirectly reflect the preservation conditions of that shale gas. • No evidence was found of external sources of He or Ar in the shale gas systems. • The relative abundances of He and Ar can reflect the accumulation and expulsion process of the shale gas. • The He/Ar ratio is related to the time available for diffusion and the sealing capabilities of the shale system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Subashi ophiolite in West Kunlun Orogenic Belt was formed at ca. 455–446 Ma. • Geochemical features indicate the Subashi ophiolite formed in a MOR setting. • Mazha-Kangxiwa mélange zone with Subashi ophiolite marks a Proto-Tethys suture. The West Kunlun Orogenic Belt (W-KOB) in the northwestern Tibetan Plateau retains critical information about the tectonic evolution of the Proto- and Paleo-Tethys during the Early Paleozoic to Mesozoic. Although a trench-arc-back arc basin model was used to address the tectonic evolution of Proto-Tethys, records about the evolution of this ocean basin remain ambiguous, particularly no studies about ages and tectonic affinities of ophiolites in the W-KOB are available. In this paper, we present new results on whole-rock elemental and Sr-Nd isotopic composition of basalts, and U-Pb zircon ages of gabbro, diabase and basalt from the Subashi ophiolite. The basalts are characterized by low REE concentrations, depleted LREEs in the chondrite normalized REE patterns, and unfractionated HFSEs in the primitive mantle normalized trace element spider diagrams, resembling normal mid-ocean ridge basalts. They have constant 87Sr/86Sr(i) values of 0.70472–0.70590 and positive ε Nd values of +7.5 to +7.9. Accordingly, it can be concluded that the Subashi ophiolite was derived from a depleted spinel lherzolite mantle source in a mid-ocean ridge setting. Zircon grains separated from basalt, diabase and gabbro have 206Pb/238U ages of 455 ± 4 Ma, 451 ± 6 Ma, and 446 ± 6 Ma, respectively, which are taken to be the crystallization ages of these rocks. Together with previously published data, our new data propose that the Mazha-Kangxiwa-Subashi ophiolitic mélange zone marks the existence of the Proto-Tethys ocean basin during the Early Paleozoic. [ABSTRACT FROM AUTHOR]

Exploration campaigns focusing on Paleozoic plays in the Egyptian north Western Desert Sallum and Faghur basins have been limited to date, and little has been done to investigate their hydrocarbon generation potential. A total of 284 shale, calcareous shale, coaly shale and siltstone side-wall core and cuttings samples, covering the rock succession that ranges from the Silurian Kohla Formation to the Turonian Abu Roash Formation were analyzed for source rock potential. In addition, eight reservoired Paleozoic–Mesozoic oil samples were geochemically analyzed. This paper systematically investigates (1) organic enrichment, hydrocarbon generation potential, and thermal maturity of Mesozoic as well as possible Paleozoic source rocks, and (2) composition and biomarker characteristics of crude oil samples in the study area from the far north Western Desert basins of Egypt. The Silurian Kohla and Basur and the Carboniferous Desouqy and Dhiffah siltstone and shale rock samples show overall poor and fair to good source rock potential for the Lower and Upper Cretaceous rock units, respectively. In contrast, high TOC (up to 4.83 wt%) and Rock-Eval S 2 (up to 6.57 mg HC/g rock) for the Devonian Zeitoun Formation samples indicates fair to very good source potential. The Middle Jurassic Khatatba Formation samples, compared with the Devonian Zeitoun Formation or other rock units in the stratigraphic column of the study area, have the highest TOC (30.1 wt%) and the highest S 2 (26.9 mg HC/g rock), indicating fair to excellent source rock potential. These high values of the Khatatba Formation are locally related to organic-rich coaly shales and calcareous shale intervals. The Rock-Eval results indicate an overall dominance of Type-III kerogen with strongly varying OI values. This highly gas-prone character for most samples was confirmed petrographically by abundant vitrinite phytoclasts and recycled organic matter. Coals and coaly shale facies from the Alam El Bueib and Khatatba formations that contain liptinitic materials may represent Type-III kerogens that are capable of generating gas with minor oil. Based on Rock-Eval T max and HI results, the Zeitoun and Khatatba samples range from early to peak oil window. This is consistent with the Ro measurements of the Paleozoic Zeitoun samples (0.65–1.02%) and the Middle Jurassic Khatatba samples (0.59–1.01%). The Faghur oils are light (35°–46° API gravity), belong to a single genetic family and are non-biodegraded based on wide-ranging n -alkanes. Abundant tricyclic diterpanes, C 24 tetracyclic terpane, C 27 Ts trisnorneohopane, diahopane, cyclohexanes, C 29 steranes and rearranged steranes and low to very low gammacerane and extended hopanes are common molecular signatures of the analyzed light oil and condensate samples. These findings indicate a relatively oxic fluvio-deltaic environment for the corresponding clay-rich coaly shale and calcareous shale source rocks that contain predominantly higher land-plants with negligible algal/bacterial organic materials. Based on saturated- and aromatic-maturity parameters, the analyzed oils were inherited from peak–late mature source rock. • The Silurian–Turonian rock succession was analyzed for source rock possibilities. • The Khatatba and Zeitoun formations are organic-rich and have reasonable hydrocarbon potential compared to the organic-lean Paleozoic and Cretaceous rock units. • Results show an overall dominance of a highly gas-prone Type-III kerogen with varying OI values. • The Faghur oils belong to a single genetic family and were derived from humic-rich source rocks. • Oil signatures indicate a single source of terrigenous coaly shale and calcareous shale deposited within fluvial–deltaic environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grenville-age terrane is identified in the Qilian orogen. • The Precambrian basement of the Qilian orogen is divided into four distinct mega-sequences. • ∼475 Ma metamorphism was related to the subduction of the Proto-Tethys Ocean. The Qilian orogen at the northeastern margin of the Tibetan Plateau records a complete history from continental breakup to oceanic basin evolution and back to continental collision during the Neoproterozoic to Paleozoic interval. The Qilian Ocean, as a branch of the Proto-Tethys Ocean, was connected to the Iapetus Ocean but is lesser known than its two more famous counterparts. This paper presents zircon U-Pb and biotite-muscovite 40Ar/39Ar isotope data from the Yemananshan Complex in the western Central Qilian belt to assess the age and provenance of late Mesoproterozoic-early Paleozoic successions in the Qilian orogen. The results indicate the Central Qilian belt is characterized by Late Mesoproterozoic-early Neoproterozoic orogenesis with magmatism from 1200 Ma to 900 Ma and clastic metasedimentary rocks deposited between 1050 and 920 Ma. Statistical analysis of detrital zircon data and auxiliary temporal information from the Qilian orogen affirms the notion that sedimentation occurred in four distinct megasequences: (1) 1950–1850 Ma, the oldest known strata, (2) 1250–920 Ma, during Grenvillian-Sveconorwegian orogenesis, (3) 840–760 Ma, the disintegration of Rodinia, and (4) 650–550 Ma, which is typical of the orogenic belts that sutured the Gondwana continental blocks. Metamorphic zircon and 40Ar/39Ar isotope data indicate early Paleozoic metamorphism at ca. 475 Ma, which overlaps with magmatic activity associated with arc-back-arc basin development in the Central Qilian belt, which was associated with subduction of the Proto-Tethys in eastern Gondwana. [ABSTRACT FROM AUTHOR]

The soaring domestic energy consumption in the Kingdom of Saudi Arabia (KSA) continues to create a demand and supply gap. Paleozoic tight sand and shale reservoirs in KSA are considered potential sources of natural gas that could meet the growing domestic demand. To enhance the exploration and exploitation of these unconventional systems, research focusing on their reservoir quality has tremendously increased in the past few decades. A challenging aspect of these Paleozoic reservoirs is that they have similar lithologies and are poorly constrained biostratigraphically. Therefore, facies analysis, stratigraphic correlation, and geosteering are problematic. This paper describes how chemostratigraphic markers are used to identify and separate individual lithologies. Three hundred and twenty (320) data points were acquired by scanning both end caps of 165 core plug samples from continuously cored sections of three Paleozoic formations. Raw elemental spectral data were acquired using a high-resolution tabletop μXRF system. Multivariate statistical analysis including principal component analysis (PCA), pairwise correlation, and hierarchical clustering of principal components (HCPC) were used to characterize the acquired geochemical values. Eleven (11) chemofacies, within three lithofacies with clearly defined boundaries, were identified. Stratigraphic distribution patterns of the geochemical signatures (e.g., Si, Ca, Mn, Al, K, and Fe), such as sharp truncation at the upper and lower bounds, clearly defined each lithofacies. Thus, key marker elements for each lithofacies and chemozones were identified, even where the lithologies appeared homogeneous. The overall results indicate sediment deposition under varied depositional settings, from fluvial to shallow-marine environments. The results demonstrate that elemental compositional analysis can be used as a discriminating tool for resolving stratigraphic uncertainties. Such data can document subtle variations among samples that appear homogeneous using other techniques. • Key marker elements were used to establish chemostratigraphy within Paleozoic sequences, Saudi Arabia. • Chemofacies and chemozones provide insight into depositional environments and alterations within lithofacies. • The approach presented will provide support for geosteering operations, in addition to reservoir characterization. [ABSTRACT FROM AUTHOR]

The Taebaeksan Basin comprises the lower Paleozoic Joseon Supergroup and the upper Paleozoic Pyeongan Supergroup, which are separated by a disconformity representing a 140 myr‐long hiatus. This paper deals mainly with the late Paleozoic paleogeographical and tectonic evolution of the Taebaeksan Basin on the basis of updated stratigraphy, sedimentation, and geochronology of the Pyeongan Supergroup. Late Paleozoic sedimentation in the Taebaeksan Basin recommenced at ~ 320 Ma and formed a thick siliciclastic succession of marginal marine and non‐marine alluvial deposits, the Pyeongan Supergroup. The Pyeongan Supergroup was deposited in a retroarc foreland basin formed by build‐up of a magmatic arc along the northern margin of the Sino‐Korean Craton. The formation of sedimentary deposits ceased at ~ 250 Ma due to the collision of the Sino‐Korean Craton and South China Craton that generated the Triassic Songnim orogeny in Korea. Diverse tectonic models have been proposed for assembly of the proto‐Korean Peninsula, but the indented wedge model is considered to best explain the geological features of the peninsula. The indented wedge model entails northward subduction of the central block of the Korean Peninsula (part of the South China Craton) beneath the northern block of the Korean Peninsula (part of the Sino‐Korean Craton) along the Sulu‐Imjingang Belt. The Taebaeksan Basin is the site for the Paleozoic strata in Korea and was tectonically a part of the Sino‐Korean Craton. The upper Paleozoic strata of the Sino‐Korean Craton were deposited in a retroarc foreland basin formed by build‐up of a magmatic arc along the northern margin of the Sino‐Korean Craton. Late Paleozoic sedimentation ceased at ~ 250 Ma due to the collision of the Sino‐Korean Craton and South China Craton that generated the Triassic Songnim orogeny in Korea. [ABSTRACT FROM AUTHOR]

The Taebaeksan Basin is located in the mid‐eastern part of the southern Korean Peninsula and tectonically belonged to the Sino‐Korean Craton (SKC). It comprises largely the lower Paleozoic Joseon Supergroup and the upper Paleozoic Pyeongan Supergroup which are separated by a disconformity representing a 140 myr−long hiatus. This paper explores the early Paleozoic paleogeographical and tectonic evolution of the Taebaeksan Basin on the basis of updated stratigraphy, trilobite faunal assemblages, and detrital zircon U–Pb ages of the Joseon Supergroup. The Joseon Supergroup is a shallow marine siliciclastic‐carbonate succession ranging in age from the Cambrian Series 2 to Middle Ordovician. The Ongnyeobong Formation is the sole Upper Ordovician volcanic succession documented in the Taebaeksan Basin. It is suggested that in the early Paleozoic the Taebaeksan Basin was a part of an epeiric sea, the Joseon Sea, in east Gondwana. The Joseon Sea was the depositional site for lower Paleozoic successions of the SKC. Early Paleozoic sedimentation in the Joseon Sea commenced during the Cambrian Stage 3 (∼ 520 Ma) and ceased by the end of the Darriwilian (∼ 460 Ma). In the early Paleozoic, the SKC was located at the margin of east Gondwana and was separated from the South China Craton by an oceanic basin with incipient oceanic ridges, the Helan Trough. The spreading oceanic ridges and associated transform faults possibly promoted the uplift of the Joseon Sea, which resulted in cessation of sedimentation and break‐up of the SKC from core Gondwana by the end of the Ordovician. The Taebaeksan Basin is the site for the Paleozoic strata in Korea and was tectonically a part of the Sino‐Korean Craton. The lower Paleozoic strata of the Sino‐Korean Craton were deposited in an epeiric sea located at the margin of east Gondwana and was separated from the South China Craton by an oceanic basin with incipient oceanic ridges. The spreading oceanic ridges and associated transform faults may have played a major role in the cessation of early Paleozoic sedimentation and break‐up of the Sino‐Korean Craton from core Gondwana by the end of the Ordovician. [ABSTRACT FROM AUTHOR]

A late Mesoproterozoic detrital zircon (DZ) age population, which was previously considered diagnostic of a link between the Lhasa terrane and northwest Australia, occurs in other Gondwanan components, thus obscuring the paleogeographic position of the Lhasa terrane in Gondwana. Here we compiled large‐n (n ≥ 300) DZ U‐Pb data from the Lhasa terrane and potential source regions in various proposed reconstructions, and attempted to synthesize the Lhasa DZ age spectra through DZ mixing modeling. Our modeling results support the Permo‐Carboniferous Lhasa terrane having received sediment from NW Australia (mainly the Perth basin) rather than India or Africa. This, in combination with stratigraphic and paleontological evidence from the northern margin of eastern Gondwana positions the Paleozoic Lhasa terrane adjacent to the boundary between Australia and India. This study suggests that the DZ mixing modeling method based on large‐n DZ data can be used effectively for constraining paleogeographic reconstruction of continents. Plain Language Summary: Present‐day eastern Asia is Earth's only major craton that has been constructed within the last 550 Ma by the successive aggregation of peripheral microcontinents that rifted from Gondwana, and thus offers special insights into how continental accretion occurs. Accurate paleogeographic reconstruction of these continental fragments is crucial for understanding the complex history of assembly of eastern Asia. As a major continental sliver, the origin of the Lhasa terrane remains highly controversial. The radiometric ages of detrital zircon (DZ) grains have been used extensively to constrain its paleogeographic position. However, a notable ca. 1,250–1,050 Ma DZ age population, once thought diagnostic of association with Australia, occurs in many other Gondwanan continents. This results in three competing models that position the Paleozoic Lhasa terrane adjacent to NW Australia, northern India or eastern Africa. We compiled large sample (n ≥ 300 grains) DZ U‐Pb data from these potential source regions, and synthesized the Lhasa DZ age spectra using these age data from each proposed reconstruction. Our results show that the Lhasa Permo‐Carboniferous sediments were sourced from NW Australia (mainly the Perth Basin) rather than India or Africa. Our findings locate the Paleozoic Lhasa terrane outboard of the boundary between Australia and India. Key Points: Detrital zircon mixing modeling indicates that the Lhasa Permo‐Carboniferous sediments came mainly from the Perth basin, AustraliaThe Paleozoic Lhasa terrane spanned the boundary interval between Australian Gondwana and Indian GondwanaThe inverse Monte Carlo modeling method based on large‐n detrital zircon data can be used in paleogeographic reconstructions of continents [ABSTRACT FROM AUTHOR]

As the largest Phanerozoic accretionary orogenic belt in the world, the Central Asian Orogenic Belt (CAOB) experienced multiple episodes of tectonic and magmatic activities in association with extensive gold mineralization during the early Paleozoic. The newly discovered Baiyinha'er gold deposit in the southwestern CAOB exemplifies a typical structure-controlled gold mineralization due tectonic compression related to oceanic–continental subduction during the closure of the Paleo-Asian Ocean. A sequence of gold-bearing quartz veins and diorite porphyry dykes are emplaced along faults and fractures in a deformed quartz diorite batholith and its host rocks. Gold mineralization is closely associated with the emplacement of quartz veins that were formed in the same stress as the diorite porphyry dykes. They are the results of continued N–S compression. Zircon U–Pb dating yielded identical ages of 433–432 Ma for the diorite porphyry dykes and their host quartz diorite batholith. Furthermore, geochemical analysis reveals that the dioritic rocks (both the batholith and the dykes) belong to a magmatic arc related to the closure of the Paleo-Asian Ocean. The tectonic–magmatic–mineralization processes in the Baiyinha'er and contiguous areas are ascribed to the prolonged oceanic-continental subduction during the closure of the Paleo-Asian Ocean in the early Silurian. Oceanic subduction beneath the Bainaimiao arc led to generation of arc magmatism, forming the quartz diorite pluton in the Baiyinha'er and contiguous areas. Subduction-related tectonic compression resulted in faulting and fracturing of the solidified diorite intrusion and subsequent emplacement of the dioritic magmas along the faults and fractures. Continued and co-axial N–S compression induced new faults and fractures that host the gold-bearing quartz veins. [ABSTRACT FROM AUTHOR]

The early Paleozoic accretionary architecture of the Alxa and Bainaimiao regions in southern Central Asian Orogenic Belt (CAOB) is still ambiguous. In particular, the subduction polarity and tectonic origin of the Bainaimiao Arc are intensely controversial. The Ganqimaodu area in Inner Mongolia provides an excellent window to address this issue. This study presents field and detrital zircon U–Pb–Hf isotopic data of Paleozoic (meta)sedimentary rocks from Ganqimaodu to investigate their provenance and tectonic settings. New field observations show that both the Ondor sum and Hadahushu groups are composed of slightly metamorphosed flysch deposits with pervasive occurrence of "block-in-matrix" structure and isoclinal folds. Two chlorite–quartz schists from the Ondor sum Group yield age peaks at ~ 425, ~ 966, ~ 1590, ~ 1930 and ~ 2564 Ma, and three sandstones from the Hadahushu Group display similar age spectrums with peaks at ~ 443, ~ 586, ~ 960, ~ 1473, ~ 1765 and ~ 2480 Ma. New detrital zircon ages constrain the maximum depositional ages of the Ondor sum and Hadahushu groups to Early Devonian. The Ondor sum and Hadahushu groups are here interpreted as an accretionary complex due to northward subduction of the South Bainaimiao Ocean based on field data and provenance analyses. Our new results combined with previous data suggest bidirectional subduction for the western segment of the South Bainaimiao Ocean during Late Cambrian to Early Devonian. We advocate an archipelago with accretionary complexes, continental fragments, and magmatic arcs for the architecture of the southern CAOB during early Paleozoic, an analogous to modern southwest Pacific accretionary system. [ABSTRACT FROM AUTHOR]

The paleogeographic position of the Xilinhot–Songliao Block (XSB) is crucial to understand the spatiotemporal relationship between the Paleo‐Asian Ocean (PAO) and East Paleo‐Tethys Ocean (EPTO) tectonic domains. However, the lack of robust early Permian paleomagnetic data in the XSB has led to uncertainty in its paleogeographic position. Here, we report a well‐dated (286.1–281.25 Ma) paleomagnetic pole (38.4°N/17.6°E, A95 = 4.0°) from andesites of the Dashizhai Formation in the XSB. We combined our paleomagnetic data with available geological and paleontological data to reconstruct the paleogeographic relationship between the PAO and EPTO. The XSB was located on the northern margin of the EPTO at ∼285 Ma, suggesting that the northern boundary of the EPTO tectonic domain extended to the southern margin of the XSB, the Hegenshan Ocean (between the XSB and the Mongolia Block) corresponds to the eastern PAO, and the XSB separated the eastern PAO and EPTO at ∼285 Ma. Plain Language Summary: The evolution of the Paleo‐Asian Ocean (PAO) and the East Paleo‐Tethys Ocean (EPTO) tectonic domains constructed the late Paleozoic paleogeographic pattern of Central and East Asia. Due to contradictions between the tectonic paleogeography and paleobiogeography of the Xilinhot–Songliao Block (XSB) during the early Permian, the spatiotemporal relationship between the two tectonic domains has been unclear. In this study, we present well‐dated paleomagnetic constraints on the paleogeographic position of the XSB at ca. 285 Ma. We provide a new reconstruction for the Northeast Asian block, which suggests that the XSB was located between the eastern PAO and the EPTO during that time and was the intermediate unit that separated the two tectonic domains. Key Points: The Xilinhot–Songliao Block (XSB) was located at ∼19.3°N on the northern margin of the East Paleo‐Tethys Ocean (EPTO) at 285 MaThe northern boundary of the EPTO tectonic domain extended to the southern margin of the XSBThe Hegenshan Ocean between the XSB and Mongolia Block was the main ocean basin of the eastern Paleo‐Asian Ocean at 285 Ma [ABSTRACT FROM AUTHOR]