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摘要:We report a new genus and species of Paleonisciformes–Cretolepis dongbeiensis gen. et sp. nov., from the Early Cretaceous Longjiang Formation in Qiqihar City, Heilongjiang Province. The new materials can be distinguished from other Paleonisciformes genera by possessing the following characteristics: a sclerotic ring composed of more than five small bones; three pieces of suborbitals; one dermohyomandibular; a jaw hanging apparently inclined anteriorly; long and tall horizontal branch of the preopercular, a short vertical branch, with the angle formed by the two branches slightly higher than 90°; a triangular dorsal fin in the middle point between the pelvic and anal fins. The discovery of Mesozoic Paleonisciformes in northeastern China adds to the biodiversity and geographic distribution of Paleonisciformes.

摘要:A new ootype collected from the Upper Cretaceous Lijiacun Formation in the Shangdan Basin, Shaanxi Province is described in this paper. Based on general external shape, size, eggshell thickness and honeycomb-like eggshell microstructure, eggs are referable to the oofamily Faveoloolithidae. Compared with other members of Faveoloolithidae, specimens described in this paper show special characteristics: adjacent pores are usually separated by two eggshell units between which often develop interspaces; columnar eggshell units are relatively closely arranged in radial view. According to these characteristics, we erect a new oogenus and a new oospecies: Duovallumoolithus shangdanensis oogen. et oosp. nov. The new discovery expands the diversity of Faveoloolithidae.

摘要:Coniopteris was a ubiquitous plant of the Jurassic and Cretaceous periods and played an important role in the flora of the time. However, its anatomical structure is relatively poorly known. The specimens of Coniopteris hymenophylloides (Brongniart) Seward described here were collected from the Yaojie Formation in Gansu Province, northwestern China. The sterile fronds are characterized as being at least bipinnate with alternate arranged linear pinnae covered by thin cuticles. Fertile fronds are linear-lanceolate, with single sorus at the margin of each fertile pinnule. In situ spores are typically trilete, triangle to subcircular in polar view, cap-shaped in equatorial view, and 37 μm in average diameter. The trilete marking is straight and narrow, generally extends to 4/5 of the spore radius. The spore surface is smooth, and parts of the exine are granulated. The epidermal cells of cuticles are irregular in shape, approximately 40–60 μm long and 10–20 μm wide. The elliptical stomatal complexes are paracytic, approximately 30 μm long and 19 μm wide, and irregularly distributed. On the basis of its epidermal structures and comparisons with extant ferns, we consider that Coniopteris displays combined features of the related extant genera.

摘要:The regular variations in magmatic activities along the Northwest Pacific plate have been little studied in spite of their importance. In this contribution, systematic analyses were conducted on tholeiitic basalts from three Ocean Drilling Program sites (Sites 304, 1149, and 801), including the petrographic features, major and trace elements, Nd isotopic compositions, and mineral structure and compositions of whole rocks. Volcanic rocks from Sites 304, 1149, and 801 belong to tholeiites and exhibit depleted light rare earth elements (LREE), large ion lithophile elemental contents (LILE), and relatively depleted Nd isotopic ratios (143Nd/144Nd=0.513139–0.513211), similar to those of normal mid-ocean ridge basalts (N-MORB). Comprehensive data on mineral compositions, whole-rock geochemistry, and geochronology demonstrate that a regular variation trend exists in the north-south direction along the Northwest Pacific plate. The 143Nd/144Nd values (0.513139–0.513211) and trace-element ratios for whole rocks (Sm/Th=15.35–30.00; Zr/Hf=28.53–35.76; Zr/Y=2.58–3.67; Th/La=0.04–0.06; Th/Y=0.33–0.70), as well as the trace-element ratios (Zr/Hf, La/Yb, Ti/Zr) of clinopyroxenes from Sites 1149 and 801 tholeiites show larger variations compared to those from Site 304 tholeiites (143Nd/144Nd=0.513185–0.513195; Sm/Th=18.19–20.58; Zr/Hf=31.07–33.26; Zr/Y=2.62–3.03; Th/La=0.05–0.06; Th/Y=0.48–0.57). Mineral zoning textures were obvious in tholeiites from Sites 1149 and 801 but were rarely observed in Site 304. These regular features were likely attributed to the differences in the heterogeneity of the magma source, the process of magmatic evolution, the plate-spreading rate, and the effective and ineffective mixing.

摘要:The Jiangaidarina granitic mass (JM) is an important part of the magmatic belt in Longmu Co–Shuanghu Suture Zone (LSSZ) in the central Tibetan Plateau. An integrated research involving whole–rock geochemistry, zircon LA–ICP–MS U–Pb ages and Hf isotopic compositions was carried out to define the timing, genesis and tectonic setting of the JM. Zircon LA–ICP–MS U–Pb ages have been obtained ranging from 210 to 215 Ma, rather than the Early Jurassic as previously thought. Fifteen granite samples contain hornblendes and show a negative correlation between P2O5 and SiO2, indicating that the JM is an I–type granite. All the granites are enriched in LREE relative to HREE, with negative Eu anomalies (Eu/Eu*=0.56–0.81), and have similar trace elements patterns, with depletion of Ba, Nb, Sr and P. These suggest that the JM was fractionated, and this is also proved by the characteristic of negative correlations between oxide elements (TiO2, MgO, FeOt, MnO, CaO) and SiO2. Almost all εHf(t) values of the granites are between –10.3 and –5.8, implying that the JM has a crustal source intimately related with the South Qiangtang Block (SQB), except for one (+10.2), showing a minor contribution from mantle source. Moreover, relatively low Na2O/K2O ratios (0.42–0.93) and high A/CNK values (0.91–1.50) reflect that the JM was predominately derived from the medium–high potassium basaltic crust, interacted with greywacke. Our new geochemical data and geochronological results imply that the Late Triassic magmas were generated in a post–collisional tectonic setting, probably caused by slab break–off of the Longmu Co–Shuanghu Tethyan Ocean (LSTO). This mechanism caused the asthenosphere upwelling, formed extension setting, offered an enormous amount of heat, and provided favorable conditions for emplacement of voluminous felsic magmas. Furthermore, the LSTO could be completely closed during the Middle Triassic, succeed by continental collision and later the slab broke off in the Late Triassic.

摘要:The Sidingheishan mafic–ultramafic intrusion is located in the eastern part of the Northern Tianshan Mountain, along the southern margin of the Central Asian Orogenic Belt in northern Xinjiang autonomous region of China. The Sidingheishan intrusion is mainly composed of wehrlite, olivine websterite, olivine gabbro, gabbro and hornblende gabbro. At least two pulses of magma were involved in the formation of the intrusion. The first pulse of magma produced an olivine-free unit and the second pulse produced an olivine–bearing unit. The magmas intruded the Devonian granites and granodiorites. An age of 351.4±5.8 Ma (Early Carboniferous) for the Sidingheishan intrusion has been determined by U-Pb SHRIMP analysis of zircon grains separated from the olivine gabbro unit. A U-Pb age of 359.2±6.4 Ma from the gabbro unit has been obtained by LA-ICP-MS. Olivine of the Sidingheishan intrusion reaches 82.52 mole% Fo and 1414 ppm Ni. On the basis of olivine-liquid equilibria, it has been calculated that the MgO and FeO included in the parental magma of a wehrlite sample were approximately 10.43wt% and 13.14wt%, respectively. The Sidingheishan intrusive rocks are characterized by moderate enrichments in Th and Sm, slight enrichments in light REE, and depletions in Nb, Ta, Zr and Hf. The εNd(t) values in the rock units vary from +6.70 to +9.64, and initial 87Sr/86Sr ratios range between 0.7035 and 0.7042. Initial 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values fall in the ranges of 17.23–17.91, 15.45–15.54 and 37.54–38.09 respectively. These characteristics are collectively similar to the Heishan intrusion and the Early Carboniferous subduction related volcanic rocks in the Santanghu Basin, North Tianshan and Beishan area. The low (La/Gd)PM values between 0.26 and 1.77 indicate that the magma of the Sidingheishan intrusion was most likely derived from a depleted spinel–peridotite mantle. (Th/Nb)PM ratios from 0.59 to 20.25 indicate contamination of the parental magma in the upper crust. Crystallization modeling methods suggest that the parental magma of the Sidingheishan intrusion was generated by flush melting of the asthenosphere and subsequently there was about 10vol% contamination from a granitic melt. This was followed by about 5vol% assimilation of upper crustal rocks. Thus, the high-Mg basaltic parental magma of Sidingheishan intrusion is interpreted to have formed from partial melting of the asthenosphere during the break-off of a subducted slab.

摘要:The north trending rifts in southern Tibet represent the E–W extension of the plateau and confirming the initial rifting age is key to the study of mechanics of these rifts. Pagri–Duoqing Co graben is located at southern end of Yadong–Gulu rift, where the late Cenozoic sediments is predominately composed of fluvio-lacustrine and moraine. Based on the sedimentary composition and structures, the fluvio-lacustrine could be divided into three facies, namely, lacustrine, lacustrine fan delta and alluvial fan. The presence of paleo-currents and conglomerate components and the provenance of the strata around the graben indicate that it was Tethys Himalaya and High Himalaya. Electron spin resonance (ESR) dating and paleo-magnetic dating suggest that the age of the strata ranges from ca. 1.2 Ma to ca. 8 Ma. Optically stimulated luminescence (OSL) dating showed that moraine in the graben mainly developed from around 181–109 ka (late Middle Pleistocene). Combining previous data about the Late Cenozoic strata in other basins, it is suggested that 8–15 Ma may be the initial rifting time. Together with sediment distribution and drainage system, the sedimentary evolution of Pagri could be divided into four stages. The graben rifted at around 15–8 Ma due to the eastern graben-boundary fault resulting in the appearance of a paleolake. Following by a geologically quiet period about 8–2.5 Ma, the paleolake expanded from east to west at around 8–6 Ma reaching its maximum at ca. 6 Ma. Then, the graben was broken at about 2.5 Ma. At last, the development of the glacier separated the graben into two parts that were Pagri and Duoqing Co since the later stages of the Middle Pleistocene. The evolution process suggested that the former three stages were related to the tectonic movement, which determined the basement of the graben, while the last stage may have been influenced by glacial activity caused by climate change.

摘要:We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying the Late Paleozoic tectonic evolution of the Xing’an Mongolian Orogenic Belt (XMOB). The rock type of the A-type granite in the Hongol area is alkali-feldspar granite, and it constitutes a western part of the Baiyinwula–Dongujimqin A-type granite belt. Zircon U–Pb geochronology yields 206Pb/238U ages ranging from 293 to 286 Ma for the alkali-feldspar granite, indicating this granitic pluton formed in the Early Permian. The alkali-feldspar granite is high in silica (SiO2=75.13wt%–80.17wt%), aluminum (Al2O3=10.59wt%–13.17wt%) and alkali (Na2O+K2O=7.33wt%–9.11wt%), and low in MgO (0.08wt%–0.39wt%) and CaO (0.19wt%–0.70wt%). It is obviously enriched in LILEs such as Rb, Th and K, depleted in HFSEs such as Nb, Ti, La and Ce, with pronounced negative anomalies of Nb, Ti, P, Eu, Sr and Ba. Its Sr–Nd–Pb isotopic compositions show positive εNd(t) (+0.72–+3.08), low TDM2 (805–997 Ma), and high radioactive Pb with (206Pb/204Pb)i of 18.710–19.304, (207Pb/204Pb)i of 15.557–15.604 and (208Pb/204Pb)i of 37.887–38.330. Petrological characteristics and geochemical data suggest that the alkali-feldspar granite in the Hongol area belongs to aluminous A-type granite. This A-type granite formed in a post-collisional extensional setting and was generated by the partial melting of felsic rocks in the middle-lower crust resulting from post-collisional slab breakoff. It is suggested that the Paleo-Asian Ocean was closed before the Permian in central Inner Mongolia.

摘要:Mesozoic magmatism is widespread in the eastern South China Block and has a close genetic relationship with intensive polymetallic mineralization. However, proper tectonic driver remains elusive to reconcile the broad intracontinental magmatic province. This study presents integrated zircon U–Pb dating, Hf isotopes and whole-rock geochemistry of the Xiwan dioritic porphyry in the NE Jiangxi ophiolitic mélange. Zircon U–Pb dating by SIMS and LA-ICP-MS methods yielded an emplacement age of ~160 Ma for the Xiwan diorite, confirming its inclusion into the Mesozoic magmatic province in SE China, instead of a component of the Neoproterozoic ophiolitic mélange genetically. The dioritic rocks have low SiO2 (58.08wt%–59.15wt%), and high Na2O (5.00wt%–5.21wt%) and MgO (4.60wt%–5.24wt%) contents with low TFeO/MgO ratios (1.02–1.09). They show an adakitic geochemical affinity but exhibit relatively low Sr/Y ratios (24.8–31.1) and high Y contents (14.6–18.3 ppm) compared to the Dexing adakitic porphyries. In addition, the Xiwan diorites have moderately evolved zircon Hf isotopic compositions (?Hf(t)=?6.1–?0.1; TDM2=1597–1219 Ma). These elemental and isotopic signatures suggest that the Xiwan diorite formed through partial melting of a remnant arc lower crust (i.e., early Neoproterozoic mafic arc-related rocks) in response to the underplating of coeval mafic magmas. In conjunction with the temporal-spatial distribution and complex geochemical characteristics of the Mesozoic magmatism, our case study attests to the feasibility of a flat-slab subduction model in developing the broad intracontinental magmatic province in SE China. The flat-slab delamination tends to trigger an asthenospheric upwelling and thus results in extensive partial melting of the overlying lithospheric mantle and lower crustal materials in an extensional setting during the Mesozoic.

摘要:Abundant mafic-ultramafic blocks and dikes occur in the area north of Zunhua City, eastern Hebei Province, and were previously suggested to be part of a late Archean ophiolitic assemblage. We employed SHRIMP zircon dating and a geochemical study on these mafic and surrounding rocks to test the ophiolite hypothesis. The SHRIMP data suggest that three metagabbro samples were metamorphosed at ~1.8 Ga. Numerous ~2.5 Ga zircons display strong oscillatory zoning, characteristic of zircons from granitoid rocks but not from gabbro, so we suggest that these are xenocrystic grains. The age of these xenocrystic zircons and their metamorphic rims suggests that these mafic blocks formed in Paleoproterozoic. The surrounding gneiss of intermediate composition also contains 2.5 Ga zircons with oscillatory zoning and 1.8 Ga metamorphic rims. Fractionated REE patterns and Nb, Ta, Zr, Hf negative anomalies to variable extent were observed in the mafic blocks and surrounding rocks, also supporting a significant difference in the chemistry of ophiolitic rocks. Our data suggest that many mafic blocks in northern Zunhua are not part of a late Archean ophiolite complex but part of a tectonically dismembered Paleoproterozoic intrusive gabbro complex. This study shows that late Paleoproterozoic metamorphism occurred in the western part of eastern Hebei Province.

摘要:The Port Island Formation (PIF), a typical Cretaceous red bed in Hong Kong, is dominated by non-fossiliferous, reddish clastic rocks, making it difficult to determine the sedimentary age of PIF precisely. Previous studies assigned the PIF to Late Cretaceous provisionally only on the basis of its stratigraphic sequence and lithology. This study identified a tuffite interlayer in the PIF and a zircon U-Pb age of 128.2±2.7 Ma by LA-ICP-MS method was obtained. It’s the first time to date the depositional age of the PIF with a reliable chronological constraint. With the support of stratigraphic evidence, we concluded that the geological age of PIF should be Early Cretaceous rather than Late Cretaceous. Based on the volcanic history of Hong Kong and Southeast China and the distribution of the PIF in Mirs Bay, it is believed that there was no volcanic activity in Hong Kong in ca. 128 Ma. The tuffite interlayer discovered in PIF was formed by the deposition of volcanic ash, which might originate from remote region outside Hong Kong, in an aquatic environment on Port Island. The identification of the tuffite interlayer, as the response to a volcanic event, has great significance not only to the studies of establishment and regional correlation of the strata system and the geological evolution in Hong Kong, but also to the study of volcanic activities in Southeast China.

摘要:The metamorphic conditions of the Upper Permian Yangjiagou Formation in eastern Changchun, China, were evaluated based on the mineral assemblage, illite crystallinity, illite polytypism, the b dimension of illite, and the chemical composition of chlorite. The pelitic rocks in the Yangjiagou Formation are characterized by illite + kaolinite + chlorite ± mixed-layer chlorite/smectite and detrital quartz + plagioclase. Illite in the formation has a crystallinity of 0.38–0.55 and comprises mixed 2M1 and 1Md polytypes, indicating a metamorphic temperature of >200°C. Based on the chemical composition of chlorite and the chlorite geothermometer, we estimated diagenetic to very low-grade metamorphic conditions with temperatures of 185°C–204°C. The b dimension of illite varies from 8.992? to 9.005?. We used a mathematical algorithm to extend Guidotti and Sassi’s (1986) diagram relating illite b dimension with temperature and pressure, and used this diagram, together with illite crystallinity and chlorite chemical composition, to semi-quantitatively estimate the formation pressure at<1.2 kbar. These reveal that the Yangjiagou Formation has experienced very low-grade metamorphism.

摘要:The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone (SSZ). However, economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone (MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr# values (100Cr/(Cr+Al)) (47.7–55.1 and 46.5–51.7, respectively) than those in the high-Cr chromitites (78.2–80.4), harzburgites (72.6–77.9) and mantle dunites (79.4–84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements (PGE). The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10–0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO2-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.

摘要:The Liziyuan gold deposit, situated on the south side of the Shangdan suture zone, West Qinling Orogen, occurs in metamorphic volcanic rocks (greenschist facies) of the early Paleozoic Liziyuan Group and in Indosinian Tianzishan monzogranite. Orebodies in the Liziyuan gold field are controlled by the ductile-brittle shear zone, and by thrusting nappe faults related to the Indosinian orogeny. In detail, this paper analyzed the geological characteristics of the Liziyuan gold field, and the Pb isotopes of the Lziyuan host rocks, granitoids (Tianzishan monzogranite and Jiancaowan syenite porphyry), sulfides, and auriferous quartz veins by multiple-collector inductively coupled plasma mass spectrometry (MC–ICP–MS). In addition, previous data on the sulfur, hydrogen, and oxygen isotopes were employed to discuss the possible sources of the ore-forming fluids and materials, and to further understand the tectonic setting of the Liziyuan gold deposit. The sulfides and their host rocks (Lziyuan Group), Tianzishan monzogranite and Jiancaowan syenite porphyry, and auriferous quartz veins have similar Pb isotopic compositions. Zartman’s plumbotectonic model diagram shows that most of the data for the deposit fall near the orogenic Pb evolutionary curve or within the area between the orogenic and mantle Pb evolutionary curves. In the Δβ–Δγ diagram, which genetically classifies the lead isotopes, most of the data fall within the range of the subduction-zone lead mixed with upper crust and mantle. This indicates that a complex source of the ore lead formed in the orogenic environment. The δ34S values of the sulfides range from 3.90 to 8.50‰ (average 6.80‰), with a pronounced mode at 5.00‰–8.00‰. These values are consistent with that of orogenic gold deposits worldwide, indicating that the sulfur sourced mainly from reduced metamorphic fluids. The isotopic hydrogen and oxygen compositions support a predominantly metamorphic origin of the ore-forming fluids, with possible mixing of minor magmatic fluids, but the late stage was dominated by meteoric water. The characteristics of the Liziyuan gold deposit formed in the Indosinian orogenic environment of the Qinling Orogen are consistent with those of orogenic gold deposits found worldwide.

摘要:The Weiquan Ag–polymetallic deposit is located on the southern margin of the Central Asian Orogenic Belt and in the western segment of the Aqishan–Yamansu arc belt in East Tianshan, northwestern China. Its orebodies, controlled by faults, occur in the lower Carboniferous volcano-sedimentary rocks of the Yamansu Formation as irregular veins and lenses. Four stages of mineralization have been recognized on the basis of mineral assemblages, ore fabrics, and crosscutting relationships among the ore veins. Stage I is the skarn stage (garnet + pyroxene), Stage II is the retrograde alteration stage (epidote + chlorite + magnetite ± hematite ± actinolite ± quartz), Stage III is the sulfide stage (Ag and Bi minerals + pyrite + chalcopyrite + galena + sphalerite + quartz ± calcite ± tetrahedrite), and Stage IV is the carbonate stage (quartz + calcite ± pyrite). Skarnization, silicification, carbonatization, epidotization, chloritization, sericitization, and actinolitization are the principal types of hydrothermal alteration. LA–ICP–MS U–Pb dating yielded ages of 326.5±4.5 and 298.5±1.5 Ma for zircons from the tuff and diorite porphyry, respectively. Given that the tuff is wall rock and that the orebodies are cut by a late diorite porphyry dike, the ages of the tuff and the diorite porphyry provide lower and upper time limits on the age of ore formation. The δ13C values of the calcite samples range from ?2.5‰ to 2.3‰, the δ18OH2O and δDV-SMOW values of the sulfide stage (Stage III) vary from 1.1‰ to 5.2‰ and ?111.7‰ to ?66.1‰, respectively, and the δ13C, δ18OH2O and δDV-SMOW values of calcite in one Stage IV sample are 1.5‰, ?0.3‰, and ?115.6‰, respectively. Carbon, hydrogen, and oxygen isotopic compositions indicate that the ore-forming fluids evolved gradually from magmatic to meteoric sources. The δ34SV-CDT values of the sulfides have a large range from ?6.9‰ to 1.4‰, with an average of ?2.2‰, indicating a magmatic source, possibly with sedimentary contributions. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the sulfides are 17.9848–18.2785, 15.5188–15.6536, and 37.8125–38.4650, respectively, and one whole-rock sample at Weiquan yields 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.2060, 15.5674, and 38.0511, respectively. Lead isotopic systems suggest that the ore-forming materials of the Weiquan deposit were derived from a mixed source involving mantle and crustal components. Based on geological features, zircon U–Pb dating, and C–H–O–S–Pb isotopic data, it can be concluded that the Weiquan polymetallic deposit is a skarn type that formed in a tectonic setting spanning a period from subduction to post-collision. The ore materials were sourced from magmatic ore-forming fluids that mixed with components derived from host rocks during their ascent, and a gradual mixing with meteoric water took place in the later stages.

摘要:Electron probe micro-analysis (EPMA) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS) have been used to investigate the principal ore minerals and coexisting metallic mineral inclusions in polished thin sections from the Tiegelongnan deposit, which consists of a high-sulfidation epithermal system (HSES) and a porphyry system (PS). Molybdenite, chalcopyrite, bornite, tennantite, enargite, digenite, anilite, covellite, and tetrahedrite have been identified by EPMA. Intergrowth, cross-cutting and replacement relationships between the metallic minerals suggest that molybdenite formed first (stage 1), followed by chalcopyrite ± bornite ± hematite (stage 2), then bornite ± Cu-sulfides ± Cu-Fe-sulfoarsenides (stage 3), and lastly Cu-Fe- sulfoarsenides ± Cu- sulfides (stage 4). Pyrite is developed throughout all the stages. Droplet-like inclusions of Au-Te minerals commonly occur in tennantite but not in the other major sulfides (molybdenite, chalcopyrite and bornite), implying that tennantite is the most important Au telluride carrier. The pervasive binary equilibrium phases of calaverite and altaite constrain fTe2 in the range from ~?6.5 to ~?8 and fS2 < ?11. The intergrowth of bornite and chalcopyrite and the conversion from bornite to digenite suggest fluctuated and relatively low precipitation temperature conditions in the HSES relative to the PS. Contrastingly, the dominance of chalcopyrite in the PS, with minor bornite, suggests relatively high temperature conditions. These new results are important for further understanding the mineral formation processes superimposed by HSES and PS systems.

摘要:The Khur metallogenic district is located in a volcanic–plutonic belt in the central Lut Block (central eastern Iran). Mineralization occurs in Middle Eocene andesitic tuff and along four main vein systems trending northwest–southeast (Shurk, Mir-e-Khash, Shikasteh Sabz and Ghar-e-Kaftar veins). Microscopic studies reveal that the veins contain bornite, chalcocite, pyrite, tennantite together with minor sphalerite and chalcopyrite as hypogene minerals and chalcocite, digenite, covellite, valleriite, malachite, azurite, atacamite, hematite, and goethite as supergene minerals. The ore bodies are accompanied by narrow but intensely developed wall rock alterations of argillization, carbonatization and silicification. Copper content reaches 6.5, 2.4, 4.2 and 5% in Mir-e-Khash, Shikasteh Sabz, Ghar-e-Kaftar and Shurk, respectively. Microthermometric measurements of quartz- and calcite-hosted fluid inclusions indicate that the mineralization might be derived from a moderately saline hydrothermal fluid at temperatures between 175–316°C. Calculated δ18O values of water in equilibrium with quartz and calcite for Khur veins suggest that the fluid might have had a magmatic source, but the 18O-depletion was developed through mixing with meteoric water. Copper deposition in Khur veins is believed to have been largely caused by mixing, although wall rock reactions may also have occurred. The Khur veins are classified as volcanic-subvolcanic hydrothermal-related vein deposits.

摘要:This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase, uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectono–thermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY Ro% model, which is constrained by vitrinite reflectance (Ro) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a. 105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43–45°C/km. The main hydrocarbon generation period ensued around 105.59–80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo–temperature was over 180°C. Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation (K1b) occurred primarily around 105.59–103.50 Ma with temperatures of 125–150°C. The second accumulation period observed in the Suhongtu Formation (K1s) occurred primarily around 84.00–80.00 Ma with temperatures of 120–130°C. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono–thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation, which is the key reason for hydrocarbon filling and accumulation.

摘要:This work investigated the pore structure characteristics and reservoir features of the fine-grained tight reservoirs in the lower member of the Xinhe Formation (J2x1) in the Xiaohu subsag, Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy (SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine-grained rocks range from 1 nm to 1.55 μm, mainly concentrated between 5 and 300 nm by low pressure N2 adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution-related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine-grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores (mostly <0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine-grained tight reservoirs and can be applicable to fine-grained reservoirs in a similar setting.

摘要:Shale gas has been the exploration focus for future energy supply in South Africa in recent time. Specifically, the Permian black shales of the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations are considered to be most prospective rocks for shale gas exploration. In this study, outcrop and core samples from the Ecca Group were analyzed to assess their total organic carbon (TOC), organic matter type, thermal maturity and hydrocarbon generation potential. These rocks have TOC ranging from 0.11 to 7.35 wt%. The genetic potential values vary from 0.09 to 0.53 mg HC/g, suggesting poor hydrocarbon generative potential. Most of the samples have Hydrogen Index (HI) values of less than 50 mg HC/g TOC, thus suggesting Type-IV kerogen. Tmax values range from 318oC to 601oC, perhaps indicating immature to over-maturity of the samples. The vitrinite reflectance values range from 2.22% to 3.93%, indicating over-maturity of samples. Binary plots of HI against Oxygen Index (OI), and HI versus Tmax show that the shales are of Type II and mixed Type II–III kerogen. Based on the geochemical data, the potential source rocks are inferred as immature to over-matured and having present-day potential to produce gas.

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摘要:Coal-based graphene quantum dots (GQDs) were successfully produced via a one-step chemical synthesis from six different?coal ranks, from which two superhigh organic sulfur (SHOS) coals were selected as natural S-doped carbon sources for the preparation of S-doped GQDs. The effects of coal properties on coal-based GQDs were?analyzed?by?means?of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit blue-green and blue fluorescence under ultraviolet?light. Anthracite-based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the high-rank bituminous coal-based GQDs are?relatively?reduced in size, with their hexagonal crystal structure being only faintly visible; the low-rank?bituminous coal-based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield (QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high-rank SHOS coal (high-rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high-rank bituminous coal with SHOS content can?be used?as a natural S-doped carbon source to prepare S-doped GQDs,?extending the?clean?utilization of?low-grade?coal.

摘要:Beijing, the capital city of China, has suffered from acute water shortage, with only 300 m3/a of water resources available per capita. In addition, Beijing has experienced a prolonged period of consecutive droughts from 1999 to 2010. Water crisis has constrained the socio-economic development of Beijing. Meanwhile, the national “South-to-North Water Transfer” (STNWT) project, which is expected to provide some relief to the water crisis in Beijing, is still under development. In order to ensure the security of water supply in Beijing before the completion of the STNWT project, several measures have been implemented to cope with droughts, including pumping groundwater from emergency well fields, water saving, recycling of water, rain and flood water harvesting, and the diversion of water from neighboring rivers and groundwater basins. Groundwater from four emergency well fields contributes the most to the public and domestic water supplies in Beijing, supplying a total volume of 1.8×109 m3. The water crisis is supposed to be mitigated by the completion of the STNWT project. After the completion of this project, more sustainable management of water resources will be implemented, including the use of aquifers as groundwater reservoirs and conjunctive use of surface water and groundwater resources.

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