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This paper studies the mineralization process and the ore-forming setting of the Kantian fluorite deposit in South China through the zircon U-Pb chronology, quartz Rb-Sr dating, whole rock geochemistry, H-O isotope and fluid inclusions. A mineralization model for the Kantian fluorite deposit is proposed as follows: The subduction of the Pacific plate during the late mid-Jurassic and late Jurassic led to the formation of several fault zones. As the subduction gradually decelerated and eventually ceased, continental extension and lithosphere thinning occurred, accompanied by upwelling of the asthenosphere. This asthenosphere upwelling facilitated melting of the lithospheric mantle, resulting in the ascent of magma into the lower crust. Consequently, the intrusion of magma into the lower crust caused substantial heat, triggering partial melting of the lower crust. The molten material then ascended along faults, generating a significant quantity of granites. During the Early Cretaceous period, the Yanshan cycle witnessed another notable phase of magmatic activity. The residual magmatic hydrothermal fluid from this period served as a source of heating, while the pre-existing fault structures provided favorable pathways and storage space. Atmospheric precipitation infiltrated into the depth along these faults, and the deep-seated residual magmatic hydrothermal fluid heated the infiltrated atmospheric water, inducing cyclic upwelling. The upward migration of hydrothermal fluid continuously extracted Ca and F elements from the granites. Ongoing interaction between the fluid and the surrounding rocks led to changes in pH, coupled with alterations in temperature and pressure, ultimately resulting in the precipitation of fluorite with associated alteration zones in the surrounding rocks. [Display omitted] • Ca and F element in the fluorite were derived through the surrounding rocks. • The ore-forming fluids belong to the NaCl-H 2 O system and exhibit characteristics of medium–low temperature, low salinity, and low density, and were derived from meteoric water. • The intrusion age of surrounding rock in Kantian fluorite deposit was 159.4 ± 2.2 Ma, and the ore-forming of fluorite was 135.6 ± 0.7 Ma. • The tectonic setting responsible for the diagenesis and mineralization processes is believed to be an intracontinental stretching environment associated with the subduction of the Pacific plate. The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H 2 O, with minor C 3 H 6. Isotope analysis indicated δD VSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18O VSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H 2 O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit. [ABSTRACT FROM AUTHOR]

The spatial-temporal extent and influence of the Mongol-Okhotsk and Paleo-Pacific tectonic regimes in northeast (NE) China and adjacent areas during late Mesozoic times have long been controversial. As a superimposed rift system which formed due to extensive intracontinental extension during the Late Jurassic to Early Cretaceous periods, the Hailar-Tamtsag basin is a key area to study the relationship between the Mongol-Okhotsk and Paleo-Pacific tectonic regimes and their superposition. With the aim of constraining the evolution of those two regimes, in this paper, the Tanan depression, which is a second-order structural unit in the western part of the Hailar-Tamtsag basin, has been chosen as the research object. On the basis of structural analysis of three-dimensional (3D) seismic data in the Tanan depression, and taking into account the controlling effect and influence of the pre-existing facies on the basin evolution, the deformation events in the Early Cretaceous can be subdivided into four periods: 1) A NW-SE trending extension during the deposition of the Tongbomiao Formation to the upper part of the second Member of the Nantun Formation; 2) A NW-SE trending compression during the deposition of the upper part of the second Member of the Nantun Formation to the first Member of the Yimin Formation; 3) A near EW trending extension during the deposition of the second Member to the lower part of third Member of the Yimin Formation; 4) A near EW trending compression during the deposition of the upper part of the third Member of the Yimin Formation. Additionally, we identify compressional structures in the basement in the southeast part of the depression, which is a key study that resulted from the Mongol-Okhotsk collisional orogeny during the Late Jurassic. The above five major deformational events make up a relatively complete tectonic deformation sequence of the Hailar-Tamtsag basin. Moreover, the deformation sequence, together with other available information from the literature in NE China and adjacent areas, including petrology, geochemistry and geochronology data, also record the whole process from the orogenic stage after the closure of the Mongol-Okhotsk Ocean, over the post-orogenic collapse of the Mongol-Okhotsk orogen, to the weakening of the influence of the Mongol–Okhotsk regime, and eventually to be replaced by the Paleo-Pacific tectonic regime. Considering that the superposition and transformation of the two tectonic regimes involves almost all the geological process in NE China and adjacent area during the late Mesozoic, the complete geological record in the Tanan depression during this period provides new constraints on the research of regional tectonic evolution, and the model of multiphase deformation is also expected to have useful implications for future studies of complex basin systems. • Subdividing the deformation events within the basin during Late Jurassic to the Early Cretaceous into five periods. • The basin was not continuously extended, and the alternation of extension and shortening occurred through the evolution. • Identifying the late Jurassic thrust fault system in the basement of the Tanan depression for the first time. [ABSTRACT FROM AUTHOR]

• Equal heat contribution from crust and mantle is identified for the system. • Granite pluton with high heat production rate is important part of the crust. • Geothermal fluid recharges from precipitation and mixes with shallow groundwater. • Fractured granite and intersected faults provide excellent circulation conduits. • Reservoir temperature is calculated as 140–143 °C with degassing and mixing correction. Hydrothermal systems occurring in granite reservoir widely exist over the world, but those can continuously supply large quantities of hot water with certain temperature for power generation are rare, e.g., TangKeng geothermal system in South China. It is unclear how the granite reservoir keeps this kind of large natural yield of geothermal water with stable temperature and the genesis study is of great importance to find similar geothermal fields for further exploitation. This paper aims to discuss the formation of TangKeng geothermal system in granite of Cretaceous period, with emphasis on heat sources, geothermal fluid circulation and reservoir temperature. Results show that average regional heat flow of 72.2 mW/m2 is composed by almost equal contribution from heat production of radioactive elements in crust and conductive heat of mantle. Extension and thinning processes of lithosphere and upwelling of magma in the asthenosphere caused the thermal erosion of the upper mantle and lower crust but doesn't induce the formation of magma chamber or partial molten in the upper crust and had very limited influences on the regional thermal state. Heat flow of the crust is mainly composed by intrusive granite pluton with high heat production value in the surface and the felsic upper crust. Geothermal fluid is recharged by the local precipitation from the surrounding mountains through regional developed NE and NW faults system. The crushed fine-middle grained biotite granite or granite with fractures and fissures of Mesozoic period provide excellent reservoir for water circulation. Interactions between regional faults and fractures in granites provide excellent conduits for additional recharge from shallow groundwater which is continuously recharged by the Rong Jiang River water during the ascending process. Reservoir temperature is calculated to be about 140–143 °C with correction of slightly CO 2 degassing and mixing. Missing of caprock for most of the areas and mixing with cold groundwater during ascending process led to the occurrence of geothermal water with lower temperature of 92 °C collected at the surface. Fractured granite reservoir with high heat productivity from radioactive elements, well developed NE and NW oriented faults system and continuous recharge from local precipitation and surface water nearby are essential for the formation of this kind of hydrothermal system. [ABSTRACT FROM AUTHOR]

Through integral studies on cores, seismics, well-logs and laboratory sediment analysis a new sequence stratigraphic framework of the Late Cretaceous first member of the Yaojia Formation in the Songliao Basin, in China's Zh ao y uan- T ai p ing ch uan (Zhy-Tpch) region, has been reconstructed. In this study, the first member of Yaojia Formation is divided into 3 three-order depositional sequences, each composed of three systems tracts, i.e. the lowstand systems tract (LST), the transgressive systems tract (TST) and the highstand systems tract (HST). Using a dense network of cored boreholes data and data acquired from a combination of spontaneous potential and electric resistivity logging methods, the paper studies the characteristics and distribution of sedimentary environments within the cyclic patterns (systems tracts) of the major depositional sequences, and ascertains that deposition of sediments in a predominantly shallow lake delta environment which prevailed in the region during the Late Cretaceous period was responsible for the creation of the first member of the Yaojia Formation. Results show that this formation is mainly composed of three sub-facies namely, the delta plain, delta front and prodelta (the shore shallow lake). Each sub-facies is further subdivided into eleven sedimentary environments including distributary channels, natural levees, crevasse splays, inter-distributary channels, flood plains, subaqueous distributary channels, inter-distributary bays, subaqueous crevasse splays, mouth bars, distal bars and sheet sands. The delta plains and delta fronts are widely developed. Deposited with frequent bifurcations, the distributary channels gradually moved towards the center of the lacustrine basin where prodelta sedimentation had hardly occurred. Meanwhile, subaqueous channels were frequently developed within the shallow water areas of the delta fronts. Sandstone facies in the distributary and subaqueous distributary channels mutually interacted and stacked up to form dendritic-like sands. Distributary channel sands formed the most favorable reservoirs available today and are considered to be the most important exploration targets for the oil industry. Overall, this study is crucial for improving the understanding of the geological and paleo-geographic record in the Zhy-Tpch region including the facies types, relationships and cyclicity in response to changes in depositional environments (i.e. sedimentation and base-level changes) that prevailed in the region during the Late Cretaceous period and hence important for the predictive aspects of the economic petroleum exploration and development in the Songliao Basin. [ABSTRACT FROM AUTHOR]

Abstract: The northwestern edge of the Tarim Basin, which contains the Kalpin Uplift and the north Bachu Uplift, lies between the South Tianshan and Tarim continental block and its tectonic evolution is closely correlated with the Tianshan. The pre-Mesozoic units are widely exposed in the northwestern edge of the Tarim Basin, which allow detailed geological observation and sample collection. In this paper, the apatite (U–Th)/He thermochronology was used to study the tectono-thermal evolution of the northwestern edge of the Tarim Basin. The sandstone samples from the Upper Neoproterozoic, Silurian, Devonian, Carboniferous and Permian units, etc. on the northwestern edge of the Tarim Basin were collected and used to determine apatite (U–Th)/He ages. The apatite He ages in the Kalpin Uplift reveal the tectonic uplift events during the Late Cretaceous (96–70Ma) and the Miocene (22–20Ma). These uplift events are linked to collisions of the Lhasa Block and the India plate with the southern Eurasian continental margin, respectively. However, apatite He ages in the north Bachu Uplift show only the Eocene event at ∼40Ma because the west Kunlun orogenic belt thrust over the southwestern edge of the Tarim Basin during the Eocene. The thermal modeling results reveal four cooling events in the Kalpin Uplift since the Late Neoproterozoic, corresponding to 460–445Ma, 350–320Ma, 220–210Ma and 20–10Ma but only one episode with 220–210Ma in the north Bachu Uplift since the Devonian. Based on the thermal modeling results, the north Bachu Uplift did not experience the cooling events at 460–445Ma, 350–320Ma and 20–10Ma shown in the Kalpin Uplift. This paper provides a new insight into the tectonic evolution of the Tianshan and the northwestern Tarim Basin. [Copyright &y& Elsevier]

In Yangtze block (South China), there is a well-developed Mesozoic thrust system extended through the Xuefeng and Wuling mountains in the southeast to the Sichuan basin in the northwest. We present 11 apatite fission-track (AFT) data and 11 (U–Th–Sm)/He ages to unravel the low temperature thermal history of a part of the system located in the eastern Sichuan basin. The fission-track data are interpreted using a grain-age deconvolution algorithm with inverse thermal modeling of track length, grain ages and mineral composition proxy data. Results suggest that apatite fission-track ages range between 99.3 ± 8.1 and 51.0 ± 4.0 Ma, and the apatite (U–Th–Sm)/He ages between 58.3 ± 3.5 Ma and 14.2 ± 0.9. The spatial distribution of these ages shows a trend decreased from SE to NW gradually, which supports the idea of a prolonged, steady-state rock uplift and erosion process across the eastern Sichuan basin. Thermal history modeling of the combined FT and (U–Th–Sm)/He datasets reveal a common three stage cooling history: (1) initial stage of rapid cooling that younger to the east during pre-Cretaceous, (2) following by a period of relative (but not perfect) thermal stability at ∼65–50 °C, (3) and then a new rapid cooling stage that initiated in all samples between ∼15 and 20 Ma. The first rapid cooling at a rate of ⩾1.5 °C/Ma is associated with coeval tectonism in nearby regions, which result in folds and faults of the eastern Sichuan basin. Early-mid Cenozoic thermal stability is contributed to the extension widely occurring in the eastern China continent at which the average cooling rate decreased to ∼0.16 °C/Ma. Causes for speculative accelerated cooling after ca . 20–15 Ma with a rate of ⩾1.2 °C/Ma may be a far-field effect of upward and eastward growth of the Tibetan Plateau but could also be related to climate effects. In a whole, this paper analyzes the several Mesozoic and Cenozoic tectonic events influence to the patters of regional denudation. [ABSTRACT FROM AUTHOR]

The Mesozoic geology in SE China is characterized by widespread Jurassic–Cretaceous magmatism. There appears, however, an episode of “magmatic quiescence” at ca. 130–110 Ma in terms of increasing high-precision isotopic age data. The causes and regional tectonic significance of this magmatic quiescence are unclear. In this paper, we report integrated in situ U–Pb, Hf and O isotope analyses of zircons from four mica schist samples along Changle–Nan'ao Metamorphic Belt in SE China coast, and use these data to discuss the provenances of these metasedimentary rocks, the timing of the regional metamorphism and their implications for the regional tectonic evolution. The majority of zircons from the mica schists are euhedral to anhedral crystals showing clear concentric zoning under cathodoluminescence (CL) images. Metamorphic zircon rims with bright luminescence are overgrown on the some of the euhedral to anhedral zoned zircons. The zoned zircons from all mica schist samples are homogeneous in U–Pb age zircon ages (between 131 and 148 Ma, peaking at 141 Ma), O isotopes (δ 18 O = 5.6 ± 0.8‰, 2SD, n = 106), and, to the less extent, Hf isotopes (εHf(T) = − 4.7 to − 1.4 for the Dongshan mica schists, and − 1.4 to 2.2 for the Putian mica schists). They are most likely detrital zircons sourced from the regional Early Cretaceous felsic volcanic rocks (the Nanyuan Formation) and/or coeval intrusions in Fujian Province. The sedimentary protoliths of these mica schists were likely deposited in fore-arc basins. The metamorphic zircon overgrowths have relatively low Th/U ratios; they are dated at ~ 130–100 Ma, with two peaks at ~ 125 Ma and ~ 108 Ma. The first metamorphic age of ~ 125 Ma is coincident with the timing of regional Early Cretaceous magmatic quiescence, while the second metamorphic age of ~ 108 Ma is consistent with the timing of reinitiation of regional Cretaceous magmatism. We use a model of collision between the West Philippines and SE China blocks to interpret our new results. According to this model, the intensive Early Cretaceous (ca. 140–130 Ma) magmatism along the coastal region of SE China was attributed to the subduction of the Paleo-Pacific plate beneath SE China. Collision between the West Philippines and SE China blocks at ~ 130–120 Ma resulted in the regional “magmatic quiescence” and formation of the Changle–Nan'ao Metamorphic Belt. Post-collisional extension triggered the reinitiation of magmatism associated with amphibolite-facies metamorphism at ~ 110 Ma. [ABSTRACT FROM AUTHOR]

Abstract: The Cretaceous tectonic evolution of South China is characterized by widespread extensional basin and dome generation, voluminous magma intrusion/eruption and associated polymetallic mineralization, all of which are of world-wide interests that have stimulated the attention of geologists for more than half a century. Due to the lack of a comprehensive understanding of regional tectonic evolution and geodynamics of South China, many controversies regarding the nature and origin of these features remain. This paper attempts to make a review by synthesizing existing structural, petrological, geochronological and geochemical data of the Cretaceous structures and magmas, which guides us to propose a three-stage tectono-thermal evolutionary history of South China during the Cretaceous period. The earliest Cretaceous (145–137Ma) tectonic stage was characterized by syn-orogenic shortening deformation and metamorphism under a NW–SE compressional setting, which generated voluminous porphyry Cu–Au ore-bearing adakitic rocks in the Lower Yangtze River Belt and gneissic granites in the coastal area. Its geodynamic origin was interpreted as combined effects of the Pacific–Izanagi ridge subduction beneath the Lower Yangtze River Belt and the Pacific subduction beneath the Cathaysia Block. This syn-orogenic shortening stage was followed by a post orogenic stage (136–86Ma) comprising two episodes of alternate extensional and shortening events. The extension (136–118Ma) in the earlier episode was dominated by a NW–SE extensional regime, it led to significant taphrogenesis manifested by large-scale extensional basins and voluminous magma intrusion/eruption; this extensional event was associated with a combination of the slab window opening during the ridge subduction and the rollback of the subducted Pacific slab. The subsequent NW–SE transpressional event led to cessation of active marginal magmatism and resulted in tectonic inversion of previous rift basins; this transpression lasted from 117Ma to 108Ma, and its driving mechanism was attributed to the collision between the eastern Asian margin and the West Philippine Block. The extension (107–86Ma) in the later episode was dominated by a WNW–ESE extensional regime, which led to a second phase of basin subsidence and produced numerous A- and I-type granites and bimodal volcanoes. The tectonic regime then changed at ca. 85Ma to WNW–ESE-oriented transpression, causing inversion of the Late Cretaceous rift basins and cessation of extension-related magmatism. The change of stress field from WNW–ESE extension to WNW–ESE transpression was related to the variations of the subducted slab dynamics, i.e., the transition from either the ESE-ward retreat to WNW-ward subduction of the Pacific slab, or the alternate stress during slab break-off. During the latest Cretaceous, a drastic change of regional tectonic stress orientation from WNW–ESE to N–S occurred in South China, the third stage predominated by N–S extension was developed, which caused a new phase of regional crustal subsidence along the youngest E–W trending extensional structures. [Copyright &y& Elsevier]

Abstract: Whether there are terrestrial responses to the Oceanic Anoxic Events (OAEs) remain enigmatic. In this paper, we report a case study in the Lower Cretaceous continental and transitional sequences of coastal southeastern China. It may represent the first late Aptian to Albian terrestrial carbon isotope record from China. Several organic-rich black shale and grayish black mudstone horizons were found to develop widely in the coastal southeastern China during the period from 113±3Ma to 99±3Ma, when the Cretaceous OAEs were recorded primarily in marine sequences. Organic carbon isotope (δ13Corg), total organic carbon (TOC), and total nitrogen (TN) were analyzed for the black shales from two sections, i.e., the Shipu transitional and Chong'an continental sections. Five negative δ13Corg excursions can be recognized for both the sections, termed as SI–SV and CI–CV events for the Shipu (S) and Chong'an (C) sections, respectively. Correlations between δ13Corg, TOC and N/C ratio suggest that the SI–SIII and CI–CIII events might have been caused by global factors, i.e., the OAE1b event based on analogs to typical OAE1b reported in the Tethyan and Pacific basins. They archived the terrestrial carbon isotope response to the OAE1b accompanied with a disturbance of carbon isotope in carbon reservoir of the global ocean–atmosphere system under a warm and humid climate. [Copyright &y& Elsevier]

The Weilasituo vein-type deposit hosted in Hercynian (Middle to Late Paleozoic) quartz diorite and Palaeozoic gneiss occurs on the western slopes of the southern Great Xing'an Range. In this paper, we present results from fluid inclusion and isotope (H, O, S, Pb) investigations on the Weilasituo deposit. We identify three stages during the ore formation: a barren pre-ore stage (stage 1), a main-ore stage with economic grade Cu–Zn–Ag mineralization (stage 2), and a barren post-ore stage (stage 3). Fluid inclusion and mineral thermometry constrain temperature intervals of approximately 243 to 333°C, 192 to 425°C, and 141 to 261°C, for the three stages, respectively. Fluids in the main-ore stage are characterized by complex NaCl–H2O–CH4–CO2 low-salinity (3.55 to 8.68wt.% NaCl equiv.) with isotopic signatures consistent with a magmatic source. These fluids evolved by mixing with local meteoric water (δ18Ofluid =1.15 to 5.15‰, δDfluid =−139.4 to −88.2‰). Measured and calculated sulfur isotope compositions of hydrothermal fluids (δ34Sfluid =−3.0 to 3.4‰) indicate that the ore sulfur was derived mainly from a magmatic source. The lead isotope ratios from the ores show mean values of 18.326, 15.553, and 38.242 for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, respectively, indicating a mantle source. Our study shows that fluid mixing and/or dilution played an important role in copper, zinc, and silver mineralization in the Weilasituo deposit. The Weilasituo and Bairendaba deposits represent a linked ore system genetically related to the late Mesozoic magmatism. The ore-forming fluids associated with the Early Cretaceous mineralization in the southern Great Xing'an Range are of magmatic in origin, and evolved by mixing with local meteoric water. These deposits preserve the signature of a mantle source for lead. However, the deposits formed at ca. 177–160Ma possess a dominantly magmatic signature with less radiogenic lead. [ABSTRACT FROM AUTHOR]

Abstract: Songliao Basin in NE China developed the most productive oilfield in the world sourced from terrestrial rocks. The main source rock of the basin includes member 1 of the Qingshankou (K2qn1) and members 1 and 2 of the Nenjiang Formation (K2nj1–2). However the exact reasons for the formation of the source rock, especially the K2qn1 are still controversial. Former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of K2qn1 but further geochemical evidence is needed. This paper explores the distinct sulfate levels that distinguish marine from fresh waters of the Songliao paleo-lake. We undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the Quantou Formation (K1q4) to top of member 1 of the Qingshankou (K2qn1). The ratio of organic carbon to the pyrite sulfur (TOC/PYS) proved the previously suggested saline conditions during the deposition of K2qn1; and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for K2qn1, but also for top of K1q4. The exact time for the beginning of marine incursion is to be determined. The marine incursion within K2qn1 is not strong and partially controlled by the fluctuation of paleo-lake level. The present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the Songliao paleo-lake, although further studies are still needed. [Copyright &y& Elsevier]

Abstract: In order to define the provenance change across the nonconformable boundary between the second and the third members of the Upper Cretaceous Nenjiang Formation (Campanian) in the north-central area of the Songliao Basin, two sandstone samples above (sample a-1 from the fourth member of the Nenjiang) and below (sample z-1 from the first member of the Yaojia Formation) the nonconformity were collected from core holes. U–Pb dating was performed on detrital zircons separated from the three sandstone samples. Detrital zircons from sample a-1 have dominant age populations of 100–110Ma, 190–220Ma, and ~1800Ma, and sample z-1 has dominant ages of 130–150Ma and ~350Ma. This paper demonstrates that the provenance of the fourth member of the Nenjiang Formation is significantly different from the first member of the Coniacian Yaojia Formation. The provenance above the nonconformity became much more complex and the eastern source increased significantly, while the western source sharply declined. The main source areas of the fourth member of the Nenjiang Formation are mainly the Zhangguangcai Range, the eastern Lesser Xiang'an Range and the southeast of Songliao Basin. The dominant provenance of the first member of the Yaojia Formation is the northern, the central and the southern Great Xing'an Range. According to the depositional ages and combining the latest seismic stratigraphic profiles in the Songliao Basin, the tectonic inversion of the eastern Songliao Basin began between 73Ma and 87Ma, which differs from the previous age of 73Ma. [Copyright &y& Elsevier]

Abstract: As a paradigm of greenhouse climate in Earth's history, the Cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate. The Songliao Basin, among the longest duration (85–90m.y.) of continental sedimentary basins, provides an excellent opportunity to recover a nearly complete Cretaceous terrestrial sedimentary record. Extensive lake deposits, ten-kilometers deep and covering an area of 260,000km2 of the Songliao Basin, provide unique, detailed records that can be tied to the global stratigraphic time scale, thereby improving our understanding of the continental paleoclimate and ecological system. The two coreholes at SKIs and SKIn sites were drilled into this basin and completed with a total length of 2485.89m of recovered core that spanned the complete middle-to-Upper Cretaceous strata in the basin. The unique geological setting of long-term continuous subsidence within the largest Cretaceous landmass in the world — makes the Cretaceous Songliao Basin of northeastern China an ideal place to study Cretaceous climate change on the continent. This paper reviews the literature on the paleogeography and paleoclimate of the northern East Asia and the Songliao Basin during the Cretaceous. Based on the climatologically sensitive deposits, oxygen isotope studies, and paleontology, the climate during the Cretaceous in the Songliao Basin was temperate and humid with relatively abundant rainfall. During the period, significant changes – four cooling, three warming, and three semiarid events – are generally consistent with the oxygen isotope data from East Asia, and the four cooling events, in Berriasian–Valanginian, Aptian–Albian, early Santonian, and Campanian–Maastrichtian, may be related to potential glaciations in Cretaceous. [Copyright &y& Elsevier]

Abstract: The Continental Scientific Drilling Project at the Cretaceous-age Songliao Basin is a drilling initiative under the framework of the International Continental Scientific Drilling Program, to recover a nearly complete Cretaceous terrestrial sedimentary record in the Songliao Basin, northeastern China. The recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the Cretaceous greenhouse world, and provide a documentation of geological events relevant to the carbon cycle during this time period. This drilling project will address significant geological questions, such as the identification of important stratigraphic boundaries and the marine-terrestrial correlations of stratigraphy, the reasons for the biotic response to the terrestrial environmental changes, the terrestrial response to the Cretaceous oceanic anoxic events, the formation of terrestrial petroleum source rocks, and the mechanisms for the Cretaceous magnetic Normal Superchron (CNS). In the first stage of this drilling project, the SKI drilling, rock cores of 2485.89m in total length were recovered and the recovery ratio reached 96.46%. A series of drilling and coring technologies including regular, confined, directional, and sealed coring, were utilized to ensure a higher recovery ratio for the core, and will be described at the end of this paper. Well loggings were conducted right after coring. Core handling and storage were arranged in such a way that the scientific research was conducted on half of each core, whereas the other half of each core was preserved for long-term storage. The upcoming second stage, the SKII drilling, will combine with data from the existing SKI to provide complete high-resolution climate records of the terrestrial environment for the whole Cretaceous time period. [Copyright &y& Elsevier]

Abstract: This paper reports on a rare magmatic suite of adakitic rocks and associated magnesian and potassium-rich magmatic enclaves and dikes, which occur in the Tunchang–Fengmu area, Hainan Island (Southeast China). LA-ICP‐MS zircon U–Pb age data show that they were generated in the late Early Cretaceous (~107Ma). The adakitic rocks, consisting mainly of granodiorites and biotite granites, are high-K calc-alkaline and have low Mg# values (0.27–0.50). They are geochemically similar to slab-derived adakites, e.g., with high SiO2, Al2O3, Sr, Sr/Y and La/Yb values, low Y and Yb contents, and negligible Eu and positive Sr anomalies. They also have relatively uniform (87Sr/86Sr)i (0.7086–0.7096), (206Pb/204Pb)i (18.50–18.61), (207Pb/204Pb)i (15.56–15.64) and (208Pb/204Pb)i (38.17–38.44) isotope ratios, with slightly variable εNd(t) (−3.85 to −6.55) and zircon in situ εHf(t) (−4.7 to +1.7) values. The mafic enclaves and dikes display disequilibrium textures (e.g., multiple-zoned clinopyroxene with low-MgO rims in contact with perthite and quartz microcrystals). They are high-K calc-alkaline and shoshonitic, and all but one sample have high Mg# (0.63–0.72) values. These mafic rocks are characterized by light rare earth element enrichment and heavy rare earth element (REE) depletion, negligible Eu and Sr and positive Pb anomalies, and Nb and Ta depletion. They have slightly more variable initial 87Sr/86Sr isotope ratios (0.7064–0.7086), εNd(t) (−5.1 to +0.1) values, and (206Pb/204Pb)i (18.35–18.50), (207Pb/204Pb)i (15.45–15.59) and (208Pb/204Pb)i (38.18–38.70) ratios. One mafic dike sample has zircon in situ ε Hf(t) values (−4.94 to −2.42) similar to those of adakitic rocks (−4.7 to +1.7) in the area. We suggest that the adakitic rocks were most likely generated by partial melting of newly underplated basaltic lower crust with arc-like geochemical characteristics, and the primitive compositions of the mafic enclaves and dikes likely originated from lithospheric+asthenospheric mantle sources metasomatized by subducted oceanic sediments or a relatively juvenile lithospheric mantle source. Mantle-derived primitive magmas likely underwent mixing at depth with minor crustally-derived felsic magmas before being injected into the adakitic magma chamber. Such injections may have broken up the magma into discrete globules and convective motion distributed the enclaves through the adakitic host. Asthenosphere upwelling due to the roll-back of the subducted Paleo-Pacific plate likely triggered the coeval late Early Cretaceous crust- and mantle-derived magmatism, resulting in the magma hybridization observed on Hainan Island. [Copyright &y& Elsevier]

Abstract: Despite more than 30 years’ studies in the Yarlung Zangbo Suture Zone (YZSZ), southern Tibet is still a region of discovery and the geological evolution of the Neo-Tethys here remains controversial. In this paper we present the new field observation, petrography, zircon U–Pb dating and geochemistry of the Zhongba mafic rocks in the western segment of the YZSZ. Zircon U–Pb analyses from a diabase using SIMS (Secondary Ion Mass Spectrometry) yielded a concordant age of 125.7±0.9Ma. All the Zhongba mafic rocks exhibit LREE enrichment (LaN/YbN =4.7–15.8) without Eu anomalies (δEu=0.97–1.01). Their Primitive-Mantle-normalized trace element patterns are similar to those of the average OIB and Hawaii alkaline basalts, as well as other OIB-type rocks already reported in the central-western YZSZ. These observations lead us to suggest the existence of a series of seamounts within the Neo-Tethys during the Early Cretaceous. These OIB-type rocks could be originated from (1) hotspot mantle; (2) near-ridge seamounts by melting-induced mixing of two distinct mantle sources; (3) late-stage magmatism fed by melts that originated from an asthenospheric window due to slab delamination. Combining literature data from the entire YZSZ, which include studies of the MORB- and IAB-type rocks and mantle peridotites, we prefer the third explanation that the OIB-type rocks represent a late-stage magmatic activity above an intra-oceanic supra-subduction zone within the Neo-Tethys. [Copyright &y& Elsevier]

Abstract: The Tongbai orogen in the middle of the Qinling–Tongbai–Dabie–Sulu orogenic belt is one of the most important portions for understanding the tectonic framework and evolution between the Sino-Korean and Yangtze cratons. In this paper, we report new U–Pb and 40Ar/39Ar age data from the Tongbai complex in order to constrain the extensional processes and late exhumation of HP/UHP terranes. Zircon U–Pb dating of different rock types in the Tongbai complex reveals the intrusion of voluminous granitic magmas at 139±2Ma, contact metamorphism and migmatization of the Triassic metamorphic enclaves at 136±2Ma, and syn-deformational emplacement of pegmatite veins at 131±1Ma. 40Ar/39Ar thermochronology on hornblende, muscovite and biotite coupled with available structural data indicates two episodes of deformation (cooling) at ca.135–120Ma and ca. 100–90Ma. The predominant ductile shearing structures, including regional subhorizontal NWW-SEE stretching lineations in the whole Tongbai complex and sinistral and dextral shear senses along its northern and southern boundaries, were formed during the first deformational episode. Regionally, the Cretaceous magmatism, metamorphism, migmatization, deformation and cooling processes in the Tongbai complex are comparable with those in the Dabie–Sulu region, suggesting the evolution of the Tongbai–Dabie–Sulu orogen within the same extensional tectonic regime during this time. The Cretaceous extensional event is thought to have resulted in the lateral eastward extrusion of the Tongbai–Dabie terrene and exhumation and final exposure of the HP/UHP rocks from mid-upper crustal depths. [Copyright &y& Elsevier]