Search

The Aolunhua Mo deposit is a typical porphyry deposit, which is located in the middle southern section of the Da Hinggan Range metallogenic belt. Here, we report LA-ICP-MS zircon U-Pb age data from the Mo-associated granitoid, together with the element geochemistry of the zircons, discussing the source material of the ore-forming rock of the deposit. The zircon data constrain the crystallization age of the granite porphyry as 135.0 ± 1.0 Ma, correlating it with the widespread Yanshanian intermediate–felsic magmatic activity. The Th/U ratio of the zircon is greater than 0.1, with a significant positive Ce anomaly (Ce* = 1.72–188.71) and a negative Eu anomaly (Eu* = 0.05–0.57). The zircons show depleted LREE and enriched HREE patterns, as well as low La and Pr contents, suggesting crystallization from crust-derived magmas. Based on the geology of the ore deposit and the age data, in combination with the regional geodynamic evolution, we infer that the Aolunhua Mo deposit was formed near the peak stage of Sn poly-metallic metallogenesis in the Da Hinggan Range region at around 140 Ma, associated with a tectonic setting, characterized by the transition from compression to extension. Based on a comparison with the newly found Mo deposits along the banks of the Xilamulun River, we propose that the Tianshan–Linxi is an important Mo-metallogenic belt. It also suggests an increased likelihood for the occurrence of Mo along the north bank of the Xilamulun River. [ABSTRACT FROM AUTHOR]

In this paper, we present new U-Pb zircon ages, Hf isotope data and major and trace elements for Early Mesozoic granitic rocks in Mohe area in the Erguna Massif of northeast China to elucidate the southward subduction of the eastern Mongol-Okhotsk Oceanic plate in Early Mesozoic. Zircons from two representative intrusions, syenogranites and monzogranites, in the Mohe area are euhedral-subhedral in shape, display oscillatory growth zoning in cathodoluminescence (CL) images, and have Th/U ratios of 0.10-0.72, and in combination these features indicating that the zircons are of igneous origin. U-Pb zircon dating results demonstrate that the syenogranites formed at 245.1 ± 1.4 Ma and monzogranites formed at 212.2 ± 1.7 Ma. These granitic rocks are characterized by high SiO2, Al2O3 and (Na2O + K2O), low TFeO, MgO, TiO2 and P2O5 concentrations, belonging to the high-K calc-alkaline series. They are enriched in LREE and large ion lithophile elements (e.g., Rb, K, and Sr), depleted in HREE and high field strength elements (e.g., Nb, Ta, Th, and Ti), as well as very weak negative Eu anomalies (Eu/Eu* = 0.48 ~ 1.01). Their zircon εHf(t) values range from −7.9 to −2.0 and range from 0.20 to 0.49, in response to their two-stage Hf model ages (TDM2) range from 1.40 Ga to 1.77 Ga range from 0.94 Ga to 1.24 Ga, respectively, indicating that primary magmas of syenogranites were derived from partial melting of newly accreted juvenile crustal material that formed from the enriched mantle during the Mesoproterozoic, monzogranites are generated by partial melting of newly accreted juvenile crustal material that formed from the depleted mantle during the Meso- to Neoproterozoic. We conclude, therefore, that the early Mesozoic granitic rocks of the Mohe area are associated with the continuous southward subduction of the Mongol-Okhotsk oceanic plate rather than the Paleo-Asian and circum-Pacific tectonic regimes. [ABSTRACT FROM AUTHOR]

Southern Hunan Province, located in the Cathaysia Block where the Shi–Hang zone and Nanling belt meet, is characterized by extensive Mesozoic magmatism and coeval polymetallic mineralization. The Huangshaping W–Mo–Pb–Zn–(Cu) deposit is representative in this area. However, the petrogenesis of the granitoids associated with the Huangshaping deposit, and their relationships with mineralization, remain undetermined. In this paper we focus on zircon U–Pb dating, whole-rock geochemistry, and Sr–Nd–Pb–Hf isotopic compositions in order to further our understanding of these issues, as well as their regional implications. The Huangshaping granitoids are characterized by two pulses of intrusive activity: a first-stage quartz porphyry and a second-stage felsite and granite porphyry, our new data show that the quartz porphyry and felsite formed at 160.5 ± 1.3 and 156.6 ± 1.4 Ma, respectively, representing a period of Late Jurassic magmatism. Granitic enclaves within the quartz porphyry crystallized at 160.2 ± 1.6 Ma, and zircons and apatites from the enclaves exhibit Hf isotopic and geochemical compositions that suggest a Palaeoproterozoic lower crustal melt as one end-member of the magma that formed the quartz porphyry, whereas another likely end-member was coeval mantle-derived magma, as indicated by the geochemistry and Sr–Nd–Pb–Hf isotopes. However, both the felsite and granite porphyry were probably derived from the melting of metamorphic basement rocks in the upper crust. The felsite clearly formed as a result of the rapid ascent and cooling of magma, whereas the granite porphyry underwent fractional crystallization. The magma sources and evolution of the granitoids, as well as their association with the Huangshaping mineralization, suggest that melting of upper crustal components controlled the W–Mo and Pb–Zn mineralization, whereas dehydration of a subducted slab provided the Cu mineralization in southern Hunan Province. [ABSTRACT FROM PUBLISHER]

Silicic, mafic and alkali intra-seam tonsteins have been known from SW China for a number of years. This paper reports on the geochemical compositions of coals and tonsteins from three seam sections of the Songzao Coalfield, SW China, and evaluates the geological factors responsible for the chemical characteristics of the coal seams, with emphasis on the influence from different types of volcanic ashes. The roof and floor samples of the Songzao coal seams mostly have high TiO2 contents, consistent with a high TiO2 content in the detrital sediment input from the source region, namely mafic basalts from the Kangdian Upland on the western margin of the coal basin. The coals from the Songzao Coalfield generally have high ash yields and are highly enriched in trace elements including Nb, Ta, Zr, Hf, rare earth elements (REE), Y, Hg and Se; some variation occurs among different seam sections due to input of geochemically different volcanic ash materials. The geochemistry of the Songzao coals has also been affected by the adjacent tonstein/K-bentonite bands. The relatively immobile elements that are enriched in the altered volcanic ashes also tend to be enriched in the adjacent coal plies, possibly due to leaching by groundwaters. The coals near the alkali tonstein bands in the Tonghua and Yuyang sections of the Songzao Coalfield are mostly high in Nb, Ta, Zr, Hf, Th, U, REE and Y. Coal samples overlying the mafic K-bentonite in the Tonghua section are high in V, Cr, Zn and Cu. The Datong coal, which has neither visible tonstein layers nor obvious volcanogenic minerals, has high TiO2, V, Cr, Ni, Cu and Zn concentrations in the intervals between the coal plies affected by mafic and alkaline volcanic ashes. This is consistent with the suggestion that a common source material was supplied to the coal basin, derived from the erosion of mafic basaltic rocks of the Kangdian Upland. Although the Songzao coal is generally a high-sulfur coal, most of the chalcophile trace elements show either poor or negative correlations with total iron sulfide contents. The absence of traditional pyrite-metal associations may reflect wide variations in the concentrations of these elements in individual pyrite/marcasite components, or simply poor retention of these elements in the pyrite/marcasite of the relevant coals. [ABSTRACT FROM AUTHOR]

This paper reports the mineralogy and geochemistry of the Early Permian No. 5 coal from the Chuancaogedan Mine, Junger Coalfield, China, using optical microscopy, scanning electron microscopy (SEM), Low-temperature ashing X-ray diffraction (LTA-XRD) in combination with Siroquant software, X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). The minerals in the No. 5 coal from the Chuancaogedan Mine dominantly consist of kaolinite, with minor amounts of quartz, pyrite, magnetite, gypsum, calcite, jarosite and mixed-layer illite/smectite (I/S). The most abundant species within high-temperature plasma-derived coals were SiO2 (averaging 16.90%), Al2O3 (13.87%), TiO2 (0.55%) and P2O5 (0.05%). Notable minor and trace elements of the coal include Zr (245.89 mg/kg), Li (78.54 mg/kg), Hg (65.42 mg/kg), Pb (38.95 mg/kg), U (7.85 mg/kg) and Se (6.69 mg/kg). The coal has an ultra-low sulfur content (0.40%). Lithium, Ga, Se, Zr and Hf present strongly positive correlation with ash yield, Si and Al, suggesting they are associated with aluminosilicate minerals in the No. 5 coal. Arsenic is only weakly associated with mineral matter and Ge in the No. 5 coals might be of organic and/or sulfide affinity. [ABSTRACT FROM AUTHOR]

The Qinling orogen is a typical composite orogen for understanding multi-stages of magmatism and orogenic processes. Many studies have been carried out on the magmatic rocks in the Qinling orogen but their petrogenesis is still controversial. This paper presents a review of all granitoid rocks based on previous and new studies of geochronology and geochemistry. Four distinct periods of granitoid magmatism, Neoproterozoic (979-711 Ma), Paleozoic (507-400 Ma), Early Mesozoic (250-185 Ma) and Late Mesozoic (160-100 Ma), have been recognized from the Qinling orogen according to zircon U-Pb ages, intrusion associations and deformation, as well as regional geology. The Neoproterozoic granitic rocks consist of three stages at 979-911, 894-815 and 759-711 Ma, respectively, corresponding to strongly deformed S-type, weakly deformed I-type and A-type granitoids. They can be interpreted as magmatic occurrences in syn-collisional, post-collisional and extensional settings, respectively, in response to old continental terranes of the Neoproterozoic tectonomagmatic events in the old continents of China, such as South China and Tarim cratons. Although this continental terrane would be involved in the Phanerozoic Qinling orogeny, the Neoproterozoic magmatic rocks are not the products of the Qinling orogenic processes. The Paleozoic magmatic rocks can be classified into three stages at 507-470, 460-422 and 415-400 Ma, respectively. The first-stage magmatism is temporally associated with ultra-high pressure metamorphism in the North Qinling terrane. These magmatic rocks are interpreted as magmatic occurrences in subductional, syn-collisional and post-collisional settings, respectively. The Early Mesozoic magmatic rocks occur in two stages at 252-185 and 225-200 Ma, respectively. The first-stage granitoids are mainly represented by I-type quartz diorites and granodiorites, and the second stage by granodiorites and monzogranites with the I-to A-type characteristics and some with rapakivi textures. Their emplacement ages and geochemical parameters such as A/CNK, KO/NaO ratios and εNd( t) values do not show any polarity change in perpendicular to subduction/collision zone. Therefore, all these Early Mesozoic granitoids are unlikely the product of continental subduction as some researchers suggested. Instead, they are plausibly related to the subduction of the Mianlue Ocean and the subsequent collision between the South China Craton and the South Qinling terrane. The Late Mesozoic granitoids were emplaced mainly at two stages of 160-130 and 120-100 Ma, and characterized by the evolution from I- to I-A- and A-type granitoids. These characteristics are consistent with the granitoid magmatic evolution from contractional to extensional settings during the Jurassic/Cretaceous in eastern China. Accordingly, the Late Mesozoic granitoid rocks in the Qinling orogen probably have a similar petrogenetic mechanism to those of the huge magmatic belt along the western Pacific margin, i.e., intra-continent magmatism related to a far-field effect of the subduction of Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

The supercontinent Rodinia existed as a coherent large landmass from 900 to 750 Ma and is now dispersed over all current major continents. Controversy has long surrounded the reconstructions of the East Asian blocks in Rodinia, especially the South China craton and nearby microcontinents. The Central Qilian block is a Precambrian microcontinent in the early Paleozoic Qilian orogenic belt, which is located in the northeastern part of the Qinghai-Xizang (Tibet) Plateau and marks the junction of the North China, South China and Tarim cratons. The formation and tectonic affinity of the Precambrian basement in the Central Qilian block is unclear, which affects our understanding of the assembly of Rodinia. The Huangyuan Group and the Maxianshan Group crop out in the eastern part of the block and represent the lower part of the basement. In this paper, we present a systematic study of the petrology, whole-rock geochemistry, and geochronology of amphibolites and orthogneisses from the Huangyuan and Maxianshan Groups. The protolith of the amphibolites was tholeiitic and calc-alkaline gabbro or gabbroic diorite formed in a continental arc environment, with laser ablation-inductively coupled plasma mass spectrometry (LAICPMS) zircon U-Pb ages of 967-957 Ma, a wide range of eHf(t) values of -3.74 to +5.06 and TDM1 model ages peaking at 1470 Ma and 1607 Ma. Minor inherited zircon grains with older ages of 1207-1515 Ma were collected from the amphibolites. The primitive magma was derived from partial melting of a spinelfacies fertile (lherzolite) lithospheric mantle that was modified by fluids and melts from a subducted slab. Fractionation of olivine, Fe-Ti oxides and plagioclase played a dominant role in the magma differentiation for gabbroic rocks in the Huangyuan Group, while fractionation of olivine and clinopyroxene controlled differentiation to form Maxianshan Group gabbros. The protolith of orthogneisses includes weakly peraluminous I-type and A2-type granites with consistent LA-ICPMS zircon U-Pb ages of 963-936 Ma, a wide range of eHf(t) values of -3.86 to +6.15 and TDM2 model age peaks at 2001 Ma and 1772 Ma. A few inherited zircon grains yield ages of 1033-2558 Ma. The peraluminous I-type granites resulted from a low-pressure partial melting process and the peraluminous A-type granites were derived from a charnockite source heated by largescale magmatic underplating. Fractionation of plagioclase, biotite, and K-feldspar from the magma played the main role during the generation of the granitoids. The intrusion of these granites is related to a back-arc extension. It is inferred that the lower part of Precambrian basement of the Central Qilian block is composed mainly of early Neoproterozoic rock assemblages formed in a trench-arc-basin system during the assembly of the Rodinia supercontinent, with probable existence of late Paleoproterozoic to Mesoproterozoic continental nuclei. Combining our results with existing data, we identify a sequence of initial intra-oceanic subduction (ca. 1121-967 Ma) in front of a continental nucleus, continuous subduction of oceanic crust beneath the continental mass with formation of a mature continental arc and a back-arc basin (ca. 967-896 Ma) and continental rifting (

[Display omitted] • The genesis of Jurassic igneous rocks in the Yanbian area was related to the subduction of the Paleo-Pacific Plate. • The Paleo-Pacific Plate started subduction beneath the Eurasian continent at the Early Jurassic. • Slab tear occurred at the Late Jurassic and this was followed by oblique subduction of the Paleo-Pacific Plate. It is widely accepted that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began during the early Mesozoic; however, the details of the subduction process remain uncertain. This paper presents new zircon U–Pb–Hf and whole-rock geochemical data for Jurassic intrusive rocks from the Yanbian area of NE China to provide a better understanding of the subduction history of the Paleo-Pacific Plate. Zircon U–Pb dating results reveal that three stages of Jurassic magmatism are recorded in the Yanbian area, namely, Early Jurassic (188–179 Ma), Middle Jurassic (172–163 Ma), and Late Jurassic (158–156 Ma). Early Jurassic intrusive rocks from the Yanbian area are predominantly calc-alkaline gabbro, gabbro-diorite, quartz monzonite, granodiorite, and syenogranite. These geochemical features and rock associations are indicative of formation in an active continental margin setting related to the initial subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The Early Jurassic granitoids were formed mainly by the partial melting of heterogeneous lower crust. The Middle Jurassic granitoids are geochemically similar to adakites and have ε Hf (t) values of + 2.0 to + 10.1. These rocks are inferred to have been derived from magmas generated by the partial melting of thickened juvenile lower-crustal material. Their formation was related to the subduction of the Paleo-Pacific Plate. Late Jurassic adakites in the Yanbian area formed in a compressional tectonic setting. Their negative ε Hf (t) values (−17.2 to − 8.6) and T DM2 ages (2025–1552 Ma) indicate that the primary magma was derived from the partial melting of ancient continental crust. Combining our data with the distribution of Late Jurassic igneous rocks in the NE Asian continental margin and the northward migration of Jurassic accretionary complexes along the margin, we conclude that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent during the Late Jurassic–earliest Early Cretaceous had a low angle of obliquity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Middle Permian adakite, arc granitoids and high fractionated granite in the northern Qaidam Block have been identified. • Various magma sources contributed to the occurrence of these granitoids in the northern Qaidam Block. • The northern Qaidam Block was an active continental arc during the Middle Permian. • A five-stage model of subduction slab roll-back and subduction zone retreat for late Late Paleozoic to Early Mesozoic tectonic evolution of the northern Qaidam Block. Origin and tectonic setting of late Late Paleozoic to Early Mesozoic igneous rocks in the northern Qaidam Block (NQ) have long been a matter of debate. In this paper, we report new zircon U-Pb ages and Hf isotopic compositions and bulk rock major and trace elemental compositions for granitoids of the Yanchangbeishan area in the NQ. The granodiorite, tonalite, granodiorite, and syenogranite yielded zircon U-Pb ages of 271.9 Ma, 262.0 Ma, 272.4 Ma and 261.3 Ma, respectively, corresponding to ε Hf (t) values are 13.04–14.32, 8.14–10.77, 8.66–11.88, and 8.22–10.43, respectively. These granitoids are compositionally I-type granites and exhibit varying degrees of enrichment in Rb, Th, U, and K, and depletion in Nb, Ta, and Ti. According to field relationships, petrology, geochronology, and geochemistry, the granitoid types can be divided into three groups: (1) ca. 272 Ma granodiorites, which are formed through partial melting of metagreywackes and amphibolites derived from depleted mantle; (2) ca. 262 Ma tonalite, which represents a typical high-silica adakite derived from partial melting of subducted oceanic crust during the evolution of depleted mantle; and (3) ca. 261 Ma syenogranite, which is formed by the partial melting and high-degree fractional crystallization of mixed crustal materials. Considering our findings and the regional geological background, we propose a five-stage tectonic evolution model of subduction slab roll-back and subduction zone retreat for the late Late Paleozoic to Early Mesozoic of NQ. [ABSTRACT FROM AUTHOR]

Scheelite, one kind of common REE-rich and U-bearing hydrothermal mineral, is extensively developed in various types of gold deposits, which can be used to record nature and timing of metallogenesis. The Zhaishang Carlin-like gold deposit in the Qinling Orogen is a giant Au deposit, hosting 127t of Au @ 2.67 g/t with economic concentrations of tungsten and antimony. The study reports two types of scheelite based on the characteristics of petrography and geochemistry. Sch A shows significant oscillatory zoning with dark gray cathodoluminescence (CL) response, whereas Sch B displays patchy textures with brighter CL response. Systematic LA-ICP-MS U–Pb dating of Sch A and Sch B yields ages of 227.1 ± 3.2 Ma and 226.2 ± 6.9 Ma, respectively. The new dates, constraining the Zhaishang Au–W mineralization to ~ 227Ma, coincide well with the western Qinling magmatism, metallogenic and tectonic events. There are significant variations in concentration, the Sch A has low REE content (mean = 41.3 ppm), negative Eu-anomaly with slightly positive Ce-anomaly, whereas Sch B, with small negative or positive Eu-anomaly, has higher REE content (mean = 247 ppm) and higher positive Ce-anomaly. The positive correlation of EuN and EuN* records oxidizing condition during the whole W mineralization event. Additionally, Sch B intergrown with selenides with an increase in the Ce-anomaly supports that the latter has higher oxygen fugacity environment. The Sr isotope signature for scheelite supports that ore-forming metals mostly inherited the host rock component, while the proportion of magma-derived Sr increased in the Sch B. Fluid–rock interactions co-precipitated Au and W caused by the release of Fe and Ca cations and the increase of pH. The study highlights that scheelite as a recorder can help in deciphering the nature and timing of metallogenesis of the studied Au–Sb–W deposit, and thus other similar Au–W deposits. [ABSTRACT FROM AUTHOR]

The Huaduoshan Cu–Mo prospect is in the Duobaoshan orefield, northeast China. The Cu–Mo mineralization occurs in the granodiorites as veinlet-disseminated. The ore-forming process can be divided into four mineralization stages: (I) quartz–pyrite–magnetite; (II) quartz–pyrite–chalcopyrite ± molybdenite; (III) quartz–pyrite–molybdenite–chalcopyrite–sphalerite; and (IV) quartz–calcite–minor pyrite. Liquid-rich two-phase aqueous (L-type), vapour-rich aqueous (V-type) and daughter-minerals three-phase (S-type) fluid inclusions (FIs) were identified at Huaduoshan. The last two types of FIs are absent in stages III and IV. The homogenization temperatures of FIs from stages I to IV are 375–438, 335–378, 283–335, and 223–267 ℃, with corresponding salinities of 2.4–50.4, 2.1–44.9, 2.7–10.1, and 1.7–7.3 wt. % NaCl eqv., respectively. The H–O isotope data of quartz in stages I (δ18OH2O = 6.1–8.0‰, δDH2O = −102.4–−94.6‰) show a magmatic origin of ore-forming fluid; the decreasing δ18OH2O (−6.8–3.2‰) and δDH2O (−117.1–−98.5‰) values of quartz in stage II–IV show the fluid mixing with meteoric water. The S–Pb isotopic values (δ34S = −2.7–0.8; 206Pb/204Pb = 18.236–18.599; 207Pb/204 Pb = 15.504–15.557; 208Pb/204Pb = 37.816–38.629) of pyrites indicate that the ore-forming materials are of magmatic origin. Fluid boiling and mixing may be the major mechanisms of ore precipitation. Zircon U–Pb age (172.1 ± 0.5 Ma) and geochemical data indicate that the ore-related granodiorites are I-type rocks formed in the subduction setting of the Paleo-Pacific Ocean Plate in the Early–Middle Jurassic. In conclusion, we propose that the Huaduoshan Cu–Mo prospect is a porphyry deposit and has potential for further exploration of porphyry Cu–Mo prospecting. [ABSTRACT FROM AUTHOR]

The paleolake level, which is controlled by the moisture balance (precipitation minus evaporation) within the lake basin, is a significant factor in determining the deposition of lacustrine organic-rich shale (LORS) across geological time, and hence influences shale oil enrichment. However, the impact of lake-level-fluctuations on shale oil enrichment of LORS is not well understood. Based on an integration of bulk geochemistry, organic petrography, pyrolysis gas chromatography, and element compositions, we address this issue using the Paleogene Biyang Depression in East China as an example. High lake levels, combined with anoxic–suboxic conditions, brackish–saline water, high productivity, and low detrital influx, are favorable for LORS deposition, which is characterized by a large distribution area and thickness, a high potential for oil generation and emplacement, and a high free shale oil content. In contrast, LORS deposited during low lake levels, with suboxic–dysoxic conditions, fresh–brackish water, low productivity, and high detrital influx, has a small distribution area and thickness, a low potential for oil generation and emplacement, and a low free shale oil content (a comparable maturity was present in all the studied LORS). Our data suggests that the elevated lake level led to higher salinity, stronger reduction conditions, higher productivity, and lower clastic inflow in the paleolake, forming LORS with higher shale oil potential. It has a positive effect on shale oil enrichment of LORS. The findings are also applicable to regional shale oil exploration. [ABSTRACT FROM AUTHOR]

Rock weathering, an important geological process on the earth's surface, plays a key role in shaping surface morphology, providing nutrients needed by the ecosystem, and regulating the global climate. However, the regimes for controlling rock weathering in different regions are still controversial. In this respect, the heavy minerals, elements, Sr-Nd isotope, magnetic susceptibility, and chromaticity of the granite weathering profile in Harbin, a high latitude area of China, were analyzed for understanding the weathering characteristics and mechanisms of the granite weathering profile in the cold area. The results indicate that the profile underwent strengthened physical weathering (large volumes of cracks in the granite parent rock) and low–moderate chemical weathering (CIA = 56~68). However, the chemical weathering does not clearly affect the composition of the weathering products, making the weathering products a good inheritance from the parent rocks, as evidenced by the binary diagram (e.g., TiO2-Zr, and La/Sc-Co/Th) and geochemical genes (LG01 and LG03). The development process of the weathering profile has been affected by the input of external materials and biological activities, as evidenced by the Sr-Nd isotopic composition, Th/Zr values, chemical depletion fractions, ΔAl/Ti ratios, χfd%, and geochemical genes (LG03). Notably, a progressively decreasing weathering degree with a reduced depth is observed in the profile, which is likely to be related to an addition of external materials and/or effects of biological activities. In addition, the weathering regime of the profile does not vary in geology time, characterized by a kinetic-limited weathering regime with a limited supply. [ABSTRACT FROM AUTHOR]

The Jian forsterite jade, so named because of its enrichment in end-member forsterite, is a new type of jade found in Ji'an County (Jilin Province, Northeast China). Tourmaline is discovered in Jian forsterite jade deposits and is characterized by magnesium enrichment. In this study, three types of magnesium tourmaline were identified from the pegmatite veins (type 1), the contact zone (type 2), and the tourmaline veins in jade (type 3). The results are shown by the main test methods, such as EPMA, Micro-XRF, and LA-ICP-MS. The substitutions of Fe2+−1Mg2+−1, (□Al3+)−1 (Na+Mg2+)−1, (□Al3+2)−1 (Ca2+R2+2)−1, etc. are inferred by the variations in the major element compositions. From type 1 to type 2 tourmaline, the content of Mg, Sr, and Sn gradually increases, the content of Fe, Zn, K, Mn, Sc, Ga, and Co gradually decreases, the content of Ca initially decreases and then increases, and the content of Na initially increases and then decreases. Type 3 tourmaline has significantly higher Si and Al than the first two types, and the content of the remaining elements lies between the above two types. We propose that tourmalines in Jian forsterite jade deposits are typically of hydrothermal origins and are mainly constrained by magnesium, which is related to the contact metasomatic metamorphism of pegmatite-related hydrothermal fluid with the Jian forsterite jade, and the chemical composition of tourmaline indicates the fluid characteristics of gradual serpentinization of Jian forsterite jade. [ABSTRACT FROM AUTHOR]

Geogas-carried metal prospecting, an integral part of deep-penetrating geochemistry, is potentially effective in the geochemical exploration of concealed ore deposits. However, its principles and applicability remain controversial. This study summarizes and discusses the progress in geogas-carried metal prospecting in China. The method comprises three constituents: geogas, nanoparticles, and their vertical transportation. Researchers have failed to determine the exact contributions of different sources of geogas. Studies on Pb isotopes, rare earth element patterns of geogas, the comparisons between metals in soil, geogas, and ore geochemistry, and characteristics of nanoscale metals in earthgas (NAMEG), confirmed the relationship between NAMEG and concealed ore deposits. A statistical analysis of field experiments and applications showed that geogas-carried metal prospecting is applicable for the geochemical exploration of magmatic and hydrothermal Cu, Au, Zn, Pb, U, Sn, and Ag deposits and is suitable for most geochemical landscapes except deserts and cold swamps. Finally, genetic models of NAMEG anomalies were constructed. High-permeability migration channels are critical in the formation of NAMEG anomalies over concealed ore deposits. Future work entails applying geogas-carried metal prospecting to certain types of ore deposits and geochemical landscapes and studying NAMEG to provide quantitative information for targeting concealed ore deposits. [ABSTRACT FROM AUTHOR]

Abstract: Geochemical data used in this paper to identify geochemical signatures associated with Fe mineralization in eastern Tianshan mineral district, China are compositional data. In order to eliminate the spurious relationships between compositions, isometric logratio (ilr) transformation is currently employed to deal with the closure effects. The opened geochemical data are further analyzed by principal component analysis. By back-transforming to the clr space, PCA results of ilr transformed data with geological meanings of their counterparts assist in recognition of spatial distributions of both intermediate-felsic igneous rocks and fault systems in the study area. In comparison with log-transformed geochemical data, the ilr transformed ones are theoretically reasonable to apply standard statistics. In addition, multivariate outliers are identified to investigate their associations with the formation of these two geological features. At the end, this paper suggests that the ilr transformation is necessary to be applied routinely before applying statistical treatments to raw geochemical data. [Copyright &y& Elsevier]

Overgrazing has been the primary cause of grassland degradation in the semi-arid grasslands of the agro-pastoral transition zone in northern China. However, there has been little evidence regarding grazing intensity impacts on vegetation change and soil C and N dynamics in this region. This paper reports the effects of four grazing intensities namely un-grazed (UG), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG) on vegetation characteristics and soil properties of grasslands in the Guyuan county in the agro-pastoral transition region, Hebei province, northern China. Our study showed that the vegetation height, canopy cover, plant species abundance and aboveground biomass decreased significantly with increased grazing intensity. Similarly, soil organic carbon (SOC) and total nitrogen (STN) in the 0–50 cm were highest under UG (13.3 kg C m−2 and 1.69 kg N m−2) and lowest under HG (9.8 kg C m−2 and 1.22 kg N m−2). Soil available nitrogen (SAN) was significantly lower under HG (644 kg N hm−2) than under other treatments (725–731 kg N hm−2) in the 0–50 cm. Our results indicate that the pasture management of “take half-leave half” has potential benefits for primary production and livestock grazing in this region. However, grazing exclusion was perhaps the most effective choice for restoring degraded grasslands in this region. Therefore, flexible rangeland management should be adopted in this region. [ABSTRACT FROM AUTHOR]

The paper presents new U–Pb zircon ages and geochemical data from early Carboniferous volcanic rocks of the Wuerkashier Mountains in the northern West Junggar region, NW China, and of the Char suture–shear zone in East Kazakhstan. The study included analysis of geological setting, major and trace elements, and rock petrogenesis. Both localities host early Carboniferous volcanic units dominated by plagioclase-porphyry andesites and dacites. A West Junggar dacite yielded a206Pb/238U age of 331 ± 3 Ma. The Junggar volcanic rocks are tholeiitic, and the Char samples are intermediate between tholeiitic and calc-alkaline. Both the Junggar and Char volcanic units are characterized by LREE enriched rare-earth spectra (La/Smn = 1.1–2.4) with Eu negative anomalies (Eu/Eu* = 0.12–1.0) and Nb-Ta minimums (Nb/Thpm = 0.15–0.35; Nb/Lapm = 0.3–0.7) on multi-element spectra. The Junggar andesites and dacites have higher REE and HFSE (Ti, Nb, Zr, Y, and Th) compared with the Char rocks, suggesting their derivation from a different mantle source. The melting modelling in the Nb-Yb system showed that the Junggar volcanic rocks formed by low- to medium- (2–5%) degree melting of depleted mantle harzburgite and spinel lherzolite. The Char volcanic rocks formed by high-degree melting (15–20%) of spinel lherzolite and garnet-bearing peridotite. The regional geology of West Junggar and East Kazakhstan and the geochemical features of the rocks under study (i.e. depletion in Nb, Ta, and Ti and enrichment in Th, and combination of LREE enrichment and HFSE depletion) all suggest a subduction-related origin of both Junggar and Char volcanic rocks. The early Carboniferous volcanic rocks of West Junggar possibly formed by subduction of the Junggar-Balkhash ocean beneath an active margin of the Kazakhstan continent, whereas those of East Kazakhstan formed by subduction of the Irtysh-Zaisan Ocean beneath an intra-oceanic arc at the active margin of the Siberian continent. [ABSTRACT FROM AUTHOR]

The conversion of farmland to forestland not only changes the ecological environment but also enriches the soil with organic matter and affects the global carbon cycle. This paper reviews the influence of land use changes on the soil organic carbon sink to determine whether the Chinese “Grain-for-Green” (conversion of farmland to forestland) project increased the rate of SOC content during its implementation between 1999 and 2010 in the hilly and gully areas of the Loess Plateau in north-central China. The carbon sink was quantified, and the effects of the main species were assessed. The carbon sink increased from 2.26×106 kg in 1999 to 8.32×106 kg in 2010 with the sustainable growth of the converted areas. The black locust (Robinia pseudoacacia L.) and alfalfa (Medicago sativa L.) soil increased SOC content in the top soil (0–100 cm) in the initial 7-yr period, while the sequestration occurred later (>7 yr) in the 100–120 cm layer after the “Grain-for-Green” project was implemented. The carbon sink function measured for the afforested land provides evidence that the Grain-for-Green project has successfully excavated the carbon sink potential of the Shaanxi province and served as an important milestone for establishing an effective organic carbon management program. [ABSTRACT FROM AUTHOR]

The Nanling metallogenic belt in South China is characterized by well-developed tungsten-tin mineralization related to multiple-aged granitoids. This belt is one of the 5 key prospecting and exploration areas among the 19 important metallogenic targets in China. Important progress has been made in recent years in understanding the Nanling granitoids and associated mineralization, and this paper introduces the latest major findings as follows: (1) there exists a series of Caledonian, Indosinian, and Yanshanian W-Sn-bearing granites; (2) the Sn-bearing Yanshanian granites in the Nanling Range form an NE-SW trending aluminous A-type granite belt that stretches over 350 km. The granites typically belong to the magnetite series, and dioritic micro-granular enclaves with mingling features are very common; (3) the Early Yanshanian Sn- and W-bearing granites possess different petrological and geochemical features to each other: most Sn-bearing granites are metaluminous to weakly peraluminous biotite (hornblende) granites, with zircon ɛ Hf( t) values of ca. −2 to −8, whereas most W-bearing granites are peraluminous two-mica granites or muscovite granites with ɛ Hf( t) values of ca. −8 to −12; (4) based on the petrology and geochemistry of the W-Sn-bearing granites, mineralogical studies have shown that common minerals such as titanite, magnetite, and biotite may be used as indicators for discriminating the mineralizing potential of the Sn-bearing granites. Similarly, W-bearing minerals such as wolframite may indicate the mineralizing potential of the W-bearing granites. Future studies should be focused on examining the internal relationships between the multiple-aged granites in composite bodies, the metallogenic peculiarities of multiple-aged W-Sn-bearing granites, the links between melt evolution and highly evolved ore-bearing felsic dykes, and the connections between granite domes and mineralization. [ABSTRACT FROM AUTHOR]

Based on comprehensive studies in petrography, petrofabric analysis and geochemistry, this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkaline hot brine under the conditions of the Mesozoic faulted lake basin. The main rock-forming mineral of this dolostone is ferruginous dolomite with a micritic structure. This dolomite mostly exhibits laminae of 0.1–1 mm thick and is often discovered with other minerals, such as albite, analcite, barite and dickite, which have at least two types of interbedded laminae. Petrogeochemistry reveals that this dolostone contains a large number of typomorphic elements of hydrothermal sedimentation, including Sb, Ba, Sr, Mn, and V. In addition, the LREE is in relatively high concentrations and possesses the typical REE distribution pattern with negative Eu anomaly. Oxygen isotope values (δ 18O PDB) range from 5.89‰ to 14.15‰ with an average of 9.69‰. The ratio of 87Sr/ 86Sr is between 0.711648 and 0.719546, with an average of 0.714718. These data indicate that the depositional environment is a stable, blocked, anoxic low-lying hot brine pool in the bottom of deep lake controlled by basement faults. The hydrothermal fluid is the alkaline hot brine formed by the combination of the infiltration lake water and mantle-derived magmatic water, consisting of many ions, including Ca 2+, Mg 2+ and Fe 2+. Under the driving flow power of magmatic heat, gravity and compaction, the hydrothermal fluid overcame the overburden pressure and hydrostatic pressure of the lake water body, and boiled to explosion, and then the explosion shattered the original laminated micritic ferruginous primary dolostone near the vent and then formed a new type of dolostone called shattered “hydroexplosion breccias”. In the low-lying, unperturbed hot brine pool, far from the vent, the laminated micritic ferruginous primary dolostone was quickly crystallized and chemicals precipitated from the hydrotherm. This study of special rocks contributes to research into the causes of the formation of lacustrine carbonate rocks and dolostone. In particular, it provides new examples and research insights for future studies of the lacustrine dolomite from the similar Mesozoic and Cenozoic basins in China. [ABSTRACT FROM AUTHOR]

In this paper, the vertical variations of heavy metal elements (including Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) in the sediments of Songhua Lake are analyzed using sediment cores. A 70-year evolutionary history of these heavy metal elements in Songhua Lake is described and the sources of the heavy metals in the sediments are investigated by evaluating the pollution characteristics of the metals in terms of their enrichment coefficients and geoaccumulation indexes. The results indicate that Cr, Cu, Mn, Ni, Pb, and Zn in the sediments originated mainly from basin erosion and were transported to the lake by rivers. Cd and Hg in the sediments also originated from basin erosion that occurred prior to the mid-1990s, and these sediments have since been overlaid by artificial pollution. The distribution of heavy metals in the sediments of Songhua Lake is influenced by many factors, including sediment composition, the relative importance of fluvial input, and artificial pollution. [ABSTRACT FROM AUTHOR]

The Southeastern Yunnan region is one of the most important polymetallic ore districts in South China. Located in the southern margin of the South China Block, these ore districts are part of a wider granite-related magmatic-hydrothermal system. Laojunshan granite intrusions, located in the western part of the Southeastern Yunnan, are closely related to W-Sn mineralisation. In this paper we report zircon U-Pb ages, geochemical and petrological characteristics for the ore-related granites in Laojunshan area. Three samples from three intrusive suites of the granitic rocks in Laojunshan intrusion have been analyzed by the LA-ICPMS zircon U-Pb techniques, yielding ages of 86.66 ± 0.42 Ma, 86.72 ± 0.47 Ma and 86.02 ± 0.48 Ma, respectively. Bulk analysis reveals that three intrusive suites are strongly-peraluminous, silica-rich, aluminum-rich and alkali-rich granites and their ACNK values fall mainly into a small range of 1.10-1.38. Moreover, all granites show enriched Rb, La and Zr and depleted Ba, Sr and Ti, as well as a uniformly flat REE-pattern with a marked negative Eu anomaly. The granites and polymetallic W-Sn mineralization possibly both occurred during the Late Coniacian. [ABSTRACT FROM AUTHOR]

The Liziyuan goldfield is located along the northern margin of the western part of the Qinling Orogen (WQO). The goldfield consists of five gold-only deposits hosted by metavolcanic rocks, and one polymetallic (Au–Ag–Pb) deposit hosted by the Tianzishan Monzogranite. As the Liziyuan goldfield appears to be spatially and temporally related to the Jiancaowan Porphyry, the study of the deposit provides a crucial insight into the relationship between tectonic-magmatic events and gold metallogenesis in the WQO. In this paper, we present whole-rock major and trace element geochemistry, and in situ zircon U–Pb and Lu–Hf isotopic data from the Tianzishan Monzogranite and Jiancaowan Porphyry. The two granitic plutons are enriched in LILEs and LREEs, depleted in HFSEs and have zircon εHf(t) values between −14.1 and −5.1 for the Tianzishan Monzogranite and between −21.0 and −8.4 for the Jiancaowan Porphyry. These characteristics indicate that the granites are derived from the crust. The Tianzishan Monzogranite has LA-ICP-MS zircon U–Pb ages of 256.1 ± 3.7 to 260.0 ± 2.1 Ma, which suggests that it was emplaced in the WQO during the convergence of the North and South (Yangtze) China cratons in the early stage of the Qinling Orogeny. In contrast, the porphyry has a LA-ICP-MS zircon U–Pb age of 229.2 ± 1.2 Ma, which is younger than the peak collision age, but corresponds to the widespread Late Triassic post-collisional granitic plutons in the WQO. The Tianzishan Monzogranite has somewhat higher Sr contents (196–631 ppm), lower Y (2.23–19.6 ppm) and Yb (0.20–2.01 ppm) contents, and a positive Eu/Eu* averaging 1.15. These characteristics suggest the pluton was derived from partial melting of the thickened crust. In contrast, the relatively higher MgO content (0.85–2.08 wt%) and Mg no. (43.4–58.2) of the Jiancaowan Porphyry indicates that insignificant amounts of subcontinental lithospheric mantle-derived mafic melts were involved in the generation of the magma. The Liziyuan goldfield is hosted by faults in greenschist-facies metamorphic rocks. Fluid inclusion studies suggest that gold was precipitated from CO2-rich, low-salinity and medium temperature fluids. This feature is consistent with the other orogenic gold deposits throughout the world. The field relationships and zircon U–Pb ages of the two granitic plutons suggest that gold mineralization is coeval with or slightly younger than the emplacement of the Jiancaowan Porphyry. Therefore, both the porphyry and deposit formed during the post-collisional stage of the Qinling Orogen. [ABSTRACT FROM PUBLISHER]

This paper presents a synthetic U-Pb and Hf isotopic study of zircons and a whole-rock geochemical study on diabase swarms that were emplaced into the Proterozoic formations in the Xuzhou-Huaibei area, the southeast margin of North China Craton. Zircons from the diabase dykes display weak oscillatory zoning in the cathodoluminescence (CL) images and show high Th/U ratios (0.91-6.90), both of which are typical of a magmatic origin. The SHRIMP and Q-ICP-MS U-Pb zircon dating results indicate that the diabase swarms were emplaced at ca. 890 Ma. Hf isotopic analysis on these zircons gives ɛ( t) values ranging from 2.26 to 14.74 and Hf model age t and t ranging from 843 to 1321 Ma and from 808 to 1779 Ma, respectively. Geochemically, the diabase swarms are characterized by a relative enrichment in LREE and LILE (Rb, Ba and La), a comparative enrichment in Cr and Ni, but a slight depletement in HFSE (Th, Nb, Ta, Zr and Hf). They are plotted in the within-plate tholeiite series on the tectonic discrimination diagrams. Taken together, these geochemical and isotopic data suggest that the primary magmas to form the diabase dykes in the Xuzhou-Huaibei area could have been derived from a transitional mantle in the Mesoproterozoic, and were most probably emplaced under a continental margin extensional setting at ca. 890 Ma. The results of this study demonstrate that the Neoproterozoic (800-900 Ma)magmatism was not restricted to the Yangtze Block, but also occurred at the southeast margin of the North China Craton. [ABSTRACT FROM AUTHOR]

Soluble organic matter had been separated from several palygorskite and bentonite samples in the Jiangsu-Anhui border area (across Jiangsu Province and Anhui Province) and Linze County in Gansu Province of China and was analyzed with the techniques and methods of organic geochemistry. The composition and distribution of hydrocarbons were analyzed by gas chromatography (GC). Organic stable carbon isotopic ratios (δC) in typical samples were determined. The abundance of soluble organic matter in all clay samples analyzed was low. In Jiangsu-Anhui samples, the preservation states of organic matter are different; hydrocarbons in organic matter have some features of aquatic plankton but are short of the input of terrigenous higher plants; organic δC in a palygorskite of Yongxiaoshan in Xuyi County, Jiangsu Province, is −6.72‰. These features may be typical of a sedimentary environment of closed or semi-closed and relatively isolated different waters near coast or seashore. On the contrary, in samples from Gansu, the preservation states of organic matter are good; the GC graphs of hydrocarbons show that the precursors of the organic matter are from a mixed source of aquatic organisms and land-sourced higher plants; organic δC of a palygorskite from Yangtai of Gansu is −15.62‰. It indicated that the sedimentary environment may be an inland salty lake. Preliminary results suggest that palygorskite minerals in the Jiangsu-Anhui area may be evolved from rapidly accumulated fine material or volcanic ash, but clays in Gansu Province may be transformed from terrigenous inorganic clastic components carried to the lake through river and then deposited. The generation process of the samples studied in the paper seems to be related to salty water. [ABSTRACT FROM AUTHOR]

The Huangshui River, an important tributary in the upper reaches of the Yellow River, has been regarded as a mother river which gestates Qinghai civilization in China. This paper presents the results of hydrogen and oxygen isotopic and water chemical analyses for the summer and winter Huangshui River water to study its seasonal recharge and major dissolved solutes. Characteristics of hydrogen and oxygen isotopes suggest that precipitation in the Qilian Mountains is the original recharge of the Huangshui River. However, in winter, the basic flow of the Huangshui River only depends on spring recharge and spring water originates from melt and infiltration of bottom layer glaciers. In summer, besides spring water, much rainfall directly recharges the Huangshui River, thus making its flux increase greatly. Water chemistry shows that the processes affecting dissolved solutes in the Huangshui River are also different between summer and winter. In summer, major ions in the river water are dominantly derived from carbonate and evaporate dissolution and anthropogenic inputs. In winter, carbonate dissolution decreases greatly while anthropogenic inputs play a much more important role for dissolved solutes in the river. Hence, further measures should be taken to lay stress on the winter Huangshui River water in order to protect the environment of the Huangshui River and reduce effects of dissolved solutes on, or prevent their pollution toward the upper Yellow River. Moreover, some measures also need to be introduced to prevent the possibility of water eutrophication caused by agricultural activities or stock raising in summer. [ABSTRACT FROM AUTHOR]

Modern analytical methods of organic petrology and organic geochemistry were used to carry out different tests like, Rock-Eval pyrolysis, Gray-King low-temperature dry distillation, and gas chromatography mass spectrometry (GC/MS) to analyse Dahuangshan oil shale. This paper also studies the abundance, the type and maturity of the organic matter, the content of total organic carbon (TOC), and hydrocarbon generating tendency of Dahuangshan oil shale. Chloroform bitumen A and its group composition were also studied. The results show that Dahuangshan oil shale is rich in organic matter and dominated by Type II1 kerogen, which has high oil generating potential. However, the degree of transformation of hydrocarbons into oil and gas is low. Group composition of chloroform bitumen A shows high content of saturated hydrocarbons and heavy components, but the content of aromatic hydrocarbons is relatively low. The composition and distribution of saturated hydrocarbons' fractions show that the sedimentary environment of Dahuangshan oil shale was moderately brackish. [ABSTRACT FROM AUTHOR]

This paper presents new zircon U Pb ages and Hf isotope data, and whole-rock geochemical and Sr Nd isotopic data, for lamprophyres in the western Shandong area of China. These data provide new insights into the nature of the lithospheric mantle beneath the eastern North China Craton (NCC) during the Early Cretaceous. The lamprophyres are divided into low-Ti (TiO 2 < 1.1 wt%; Ti/Y < 270) and high-Ti (TiO 2 > 2 wt%; Ti/Y > 370) suites, where the Xiaya and Jingziyu minettes are defined as low-Ti lamprophyres and the Jingziyu pyroxene lamprophyres are defined as high-Ti lamprophyres. The igneous zircons yield weighted-mean ages of 126, 132, and 130 Ma for the low- and high-Ti lamprophyres, respectively, indicating these units formed during the Early Cretaceous. The inherited zircons within the Xiaya and Jingziyu minettes define six (2517, 1852, 725, 375, 276, and 236 Ma) and two (2523 and 462 Ma) main age populations, respectively. In comparison, the inherited zircons from the Jingziyu pyroxene lamprophyres yield two main age populations (2523 and 1848 Ma). The low-Ti lamprophyres are enriched in the light rare earth elements (LREE) and large-ion lithophile elements (LILE), depleted in the heavy REE (HREE) and high-field-strength elements (HFSE), and have small negative Eu anomalies. In comparison, the high-Ti lamprophyres are enriched in the LREE but are slightly depleted in the HFSE. The low-Ti lamprophyres also have high 87Sr/86Sr(t) ratios (0.7121–0.7123), low ε Nd (t) values (−18.81 to −18.62), and contain igneous zircons with relatively high ε Hf (t) values (generally between −9.94 and −3.36). In comparison, the high-Ti lamprophyres have 87Sr/86Sr(t) ratios of 0.7066–0.7068, ε Nd (t) values from −5.01 to −4.64, and contain igneous zircons with ε Hf (t) values from −11.77 to −8.50. These data indicate the low-Ti lamprophyres formed from primary magmas generated by the partial melting of an enriched region of the lithospheric mantle that was previously strongly modified jointly by subduction breakoff of the downgoing Yangtze Craton basement material and delamination of the lower continental crust within the NCC. In comparison, the magmas that formed the high-Ti lamprophyres were generated by the partial melting of an enriched region of the lithospheric mantle that was weakly modified by interaction with the lower continental crust of the NCC. Both the low- and high-Ti lamprophyres formed in an extensional tectonic environment during lithospheric thinning, and the presence of these two suites of lamprophyres indicates that lithospheric thinning of the eastern NCC peaked during the Early Cretaceous. • Low- and high-Ti lamprophyres in the western Shandong area formed during the Early Cretaceous. • These lamprophyres indicate that peak lithospheric thinning of the eastern NCC occurred during the Early Cretaceous. • Delamination was an important process during the destruction of the NCC. [ABSTRACT FROM AUTHOR]

Highlights • There are sanukitoids and anatectic granites in the Bundelkhand Craton. • U-Pb zircon dating of a sanukitoid yielded a crystallization age of 2577 ± 16 Ma. • Sanukitoids are derived from a crustal source. • Sanukitoids and anatectic granites formed in a subduction-collision environment. Abstract In this paper, we present in situ zircon U–Pb ages as well as whole-rock elemental and Sm-Nd isotopic compositions for late Archean sanukitoids of the Bundelkhand Craton, India. The LA–ICP–MS zircon U–Pb dating results of the sanukitoids (s.l.) indicate that these rocks were emplaced at 2577 ± 16 Ma, with inherited zircon at an age of 2644 ± 25 Ma, and are coeval with high-K anatectic granites (2544–2583 Ma). The sanukitoids (s.l.) are characterized by high-alumina (15–16 wt.%), Mg# (27–50) and TiO 2 (0.31–0.87 wt.%). They have a strongly enriched signature in terms of incompatible trace elements (LREEs and LILE) pointing to a subduction-related or crustal source. The high-K anatectic granites are characterized by Al 2 O 3 (12–15 wt.%), Mg# (13–39) and TiO 2 (0.06–0.8 wt.%); they have enriched and variable concentrations of LILEs and REEs; and negative Eu anomalies (Eu/Eu* = 0.15–0.93). The whole-rock ε Nd (t) values (−3.64 to −1.66) indicate a crustal component. These isotopic and geochemical characteristics indicate that the sanukitoid plutons originated from the mixing of metasomatized mantle melts with anatectic melts and were followed by homogenization at shallow levels of emplacement, whereas the high-K anatectic granites indicate reworking of the pre-existing TTG crust during the cratonic stabilization ca. 2.5 Ga. This interpretation suggests a temporal evolution from TTG-domination through sanukitoids (s.l.) to anatectic leucogranites by an internal reworking of the continental crust, involving subduction-collision environments in the late Archean era. Such magmatic events and tectonics during the late-Archean in the Bundelkhand Craton resemble other Archean cratons, such as the Dharwar, North China, Karelian, Superior Province, Pilbara, Kaapvaal and Amazonian. [ABSTRACT FROM AUTHOR]

• The Jinchang gold-rich porphyry deposit has experienced two mineralization phases. • It includes early Au–Cu (∼114 Ma) and late Au-only mineralization (103–101 Ma). • Jinchang deposit was formed by the subduction roll-back of the Paleo-Pacific Plate. Whether multiple mineralization styles in porphyry deposits are the result of one or multiple pulses of magmatism is unknown. In this paper, we present new age and geochemical data on the Jinchang porphyry gold-copper (Au-Cu) deposit, an important deposit in NE China and in the eastern Central Asian Orogenic Belt (CAOB). Field geological study suggests that both the mineralization and ore-causative magmatism at Jinchang are multiphase. LA-ICP-MS zircon U-Pb dating of the monzogranite ore host yielded 197 ± 1 Ma, which is considerably older than the ore-causative monzonite (115 ± 3 Ma) and granodiorite (107 ± 2 Ma). Molybdenite Re–Os dating on the breccia pipe-hosted Au-Cu ores yielded a well-defined isochron age of 114 ± 3 Ma, coeval to the monzonite emplacement. The Au-Cu mineralization was followed by another phase of crypto-explosive breccia pipe-hosted, disseminated/vein-type Au mineralization. This Au-only mineralization phase was auriferous pyrite Re–Os dated to be 103–101 Ma, coeval to the granodiorite emplacement. Geochemically, the monzonite and granodiorite are enriched in LILEs and LREEs, but depleted in HFSEs and HREEs. The ore-causative rocks are I-type and display continental arc geochemical affinities. We suggest that the monzonite and granodiorite were generated in an intracontinental extensional setting, probably caused by the Early Cretaceous subduction roll-back of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Oil seepage is one of the most important characteristics of hydrocarbon formation, and understanding oil seepage is crucial for oil-gas exploration and the assessment of petroleum resources. Remote sensing and geochemical methods have the same material and theoretical bases for extracting oil and gas information from underlying strata and the identification of media features. As an emerging exploration method, hyperspectral remote sensing is efficient compared with traditional geochemistry because it is a finer, and sometimes more directly quantitative method for determining the specific mineral anomaly content. Hence, the use of both methods together is important. This paper describes the analysis of hyperspectral remote sensing data and the extraction of abnormal index information, including the level of carbonate alteration and the content of acidolytical hydrocarbons, pyrolysis hydrocarbons, headspace gas, and ferric and ferrous ions. The two methods have mutual authentication, and they are complementary and are useful in oil-bearing areas. When these methods are integrated, the acidolytical hydrocarbon index is the most effective geochemical index and is better at characterizing the oil field distribution than other indices. Also, hydrocarbon geochemical anomalies occurring in oil fields generally show continuous distribution points and are consistent with oil reservoirs. Consequently, a 3D model was established to comprehensively utilize hyperspectral remote sensing and geochemical data to determine the distribution of petroleum reservoirs efficiently as well as to delineate oil- and gas-bearing prospects. There is great potential for determining oil- and gas-bearing fields through the integration of hyperspectral and geochemical data. [ABSTRACT FROM AUTHOR]

The Late Palaeozoic Solonker‐Xar Moron‐Changchun‐Yanji Suture (SXCYS) is considered to mark the location of the final closure of the Paleo‐Asian Ocean, which separated the North China Craton to the south and the amalgamated blocks to the north in Northeast China. There has always been controversy about its eastern extension in Northeast China and the final closure time of the Paleo‐Asian Ocean. To explore this issue, we collected gabbro and quartz‐diorite samples in the Hunchun area for the genesis of mafic magma and age dating, and five groups of Permian to Triassic sandstones belonging to both sides of the potential suture locations in the middle and east Jilin Province for the provenance analysis to discuss the final closure time of the Paleo‐Asian Ocean and the possible positions of the eastward termination of the SXCYS. The gabbro reveals a Middle Permian concordia average age of 266.9 ± 5.2 Ma, and the quartz diorite reveals a Late Permian Concordia average age of 258.8 ± 4.8 Ma. Lithological and geochemical analysis reveal the two rock samples belong to low‐K arc tholeiites from the oceanic island and calk‐alkaline volcanics from the active continental margin, respectively, which implies that during the middle to late Permian, the SW margin of the Jiamusi–Khanka Block (JB) continuously experienced the subduction process from the Paleo‐Asian Ocean Plate. The final closure time of the Paleo‐Asian Ocean should be later than the Late Permian. Meanwhile, four groups of sandstone from the east Jilin reveal typically Jiamusi–Mongolia Block (JMB) provenance features, with age components of ~500 Ma, ~0.9–1.5 Ga implying that the Wangqing, Hunchun, Kaishantun area belongs to the northern part of the SXCYS from late Early Permian to Middle Triassic, with youngest age components of 288.2 ± 2.8, 275.5 ± 1.8, 250 ± 1.7, and 244.9 ± 1.7 Ma, respectively. The late Early Permian sandstone from the middle Jilin reveals the youngest age component of 273.8 ± 3.4 Ma and the age component of 487 ± 3 Ma also revealing JMB feature. Comparing to previous studies, we propose that the Paleo‐Asian Ocean finally closed during Middle to Late Triassic. A possible ENE fault separates the eastern extension of SXCYS into two parts, which means the possible position of the eastward extension of the SXCYS should go along the Wangqing‐Kaishantun with NNW direction in the west, Hunchun‐Laoheishan with NW direction in the east. [ABSTRACT FROM AUTHOR]

Abstract This paper uses coal-measure shales from Carboniferous-Permian in Yushe-Wuxiang Block as an example to study the physical properties of transitional coal measure shales, including geochemical properties (e.g. total organic carbon content (TOC), organic matter maturity and hydrocarbon generation potential); mineral composition determined by X-ray diffraction (XRD) and pore structure characteristics determined by gas adsorption methods. The results indicated that the transitional coal measure shales in Yushe-Wuxiang area mostly comprise type III kerogen and are mostly in the over-mature stage, with shales in the range of 1.86%–3.36% R o. The TOC of transitional shales varied significantly, ranging from 0.10% to 34.37%. Clay minerals and quartz are major minerals in transitional shales, while the predominant clay minerals are illite-smectite mixed clay (I/S) and kaolinite. The total pore volume (TPV) and pore specific surface area (SSA) of investigated mud shales varies from 0.0071 to 0.023 cm3/g and 8.4059–18.2888 m2/g, respectively. The transitional shales mostly provide mesopores and macropores, whereas the micropores provide the main SSA. The TOC content has a distinct effect on the porosity and micropores volume but contributes little to the TPV and volumes of macropores and mesopores. Clay minerals are positively correlated with porosity, TPV and volumes of each class of pores, while quartz has an opposite effect. In the over-maturity stage, the increase of organic matter maturity will inhibit the development level of pores in shale. For the coal measure shales, I/S and illite contribute most to the pore development. Highlights • TOC is positively correlated with porosity and micropore volume. • Clay minerals are positively correlated with pore volumes. • Quartz inhibits the development level of transitional coal measure shales. • The development and evolution of pores was mainly attributed to the presence of I/S and illite. [ABSTRACT FROM AUTHOR]

Geochemical studies on REE, trace elements and oxygen isotopes from metamorphic veins and their host metasedimentary rocks in the Zhoutan Group at two localities, Xiangshan and Yihuang, in central Jiangxi Province have been conducted in this paper. The results show that the metamorphic quartz veins inherited the REE and oxygen isotope geochemical characteristics from their host rocks, suggesting that the vein-forming fluids were derived from the host rocks. Additionally, fractionation degrees of the trace element pairs Zr-Hf, Nb-Ta, Y-Ho and U-Th in the veins are different from those of their host rocks. It is also indicated that the veins are the products of the fluids. The metamorphic veins within the Zhoutan Group metasedimentary rocks were formed principally as a result of lateral diffusion of the metamorphic fluids. [ABSTRACT FROM AUTHOR]

This paper reports a geochemical study of trace metals and Pb isotopes of sediments from the lowermost Xiangjiang River, Hunan province (P. R. China). Trace metals Ba, Bi, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Cd, Sn, Sb, Pb, Tl, Th, U, Zr, Hf, Nb and Ta were analyzed using ICP-MS, and Pb isotopes of the bulk sediments were measured by MC-ICP-MS. The results show that trace metals Cd, Bi, Sn, Sc, Cr, Mn, Co, Ni, Cu, Zn, Sb, Pb and Tl are enriched in the sediments. Among these metals, Cd, Bi and Sn are extremely highly enriched (EF values >40), metals Zn, Sn, Sb and Pb significantly highly (5 < EF < 20), and metals Sc, Cr, Mn, Co, Ni, Cu and Tl moderately highly (2 < EF < 5) enriched in the river sediments. All these metals, however, are moderately enriched in the lake sediments. Geochemical results of trace metals Th, Sc, Co, Cr, Zr, Hf and La, and Pb isotopes suggest that metals in the river sediments are of multi-sources, including both natural and anthropogenic sources. Metals of the natural sources might be contributed mostly from weathering of the Indosinian granites (GR) and Palaeozoic sandstones (PL), and metals of anthropogenic sources were contributed from Pb-Zn ore deposits distributed in upper river areas. Metals in the lake sediments consist of the anthropogenic proportions, which were contributed from automobile exhausts and coal dusts. Thus, heavy-metal contamination for the river sediments is attributed to the exploitation and utilization (e.g., mining, smelting, and refining) of Pb-Zn ore mineral resources in the upper river areas, and this for the lake sediments was caused by automobile exhausts and coal combustion. Metals Bi, Cd, Pb, Sn and Sb have anthropogenic proportion of higher than 90%, with natural contribution less than 10%. Metals Mn and Zn consist of anthropogenic proportion of 60-85%, with natural proportion higher than 15%. Metals Sc, Cr, Co, Cu, Tl, Th, U and Ta have anthropogenic proportion of 30-70%, with natural contribution higher than 30%. Metals Ba, V and Mo might be contributed mostly from natural process. [ABSTRACT FROM AUTHOR]

This paper reports the systematic study on petrology, geochemistry, LA ICPMS zircons U-Pb dating, and in situ Hf isotope geology of the four plutons in the central-southern Jiangxi Province, an important part of the South China Block. In the outcrops, rocks are gradually changed from wall rock (slate or schist) to pluton (gneissic granite); some residual blocks of sandy rock occur in the margin of pluton, and the foliations of residual blocks are parallel to those of both wall rock and gneissic granite. The thin-section observations show that the four plutons contain peraluminous minerals such as muscovite and sillimanite. The flattened and elongated feldspar and quartz grains are often visible in the gneissic granite, parallel to direction of lineation, suggesting that the granitic rock were subjected to a strong ductile shearing. Geochemically, the A/CNK values from 13 granitic samples are between 1.03 and 1.37 with an average of 1.16, indicating that the granites are of strongly peraluminous plutons. The REE compositions of the 13 samples are similar, showing higher ΣREE contents, with enrichment in LREEs, depletion in Eu and REE patterns with relative LREE-enrichment and negligible Eu anomalies. They show enrichment in Rb, Th, U and depletion in Ba, Sr, Nb, Ti, belonging to a low Ba-Sr type of granite. Thus, the four bodies should be derived from the same magmatic source. Zircons used as U-Pb dating mostly exhibit euhedral shape and high Th/U values from 0.52 to 1.54 with an average of 1.08, suggesting that most zircons are of magmatic genesis. The zircons from four plutons yielded rather similar Pb/U vs. Pb/U concordia ages: 436.1±5.7 Ma for the Tangwan granite, 440.6±4 Ma for the Jiekou gneissic granite, 435.9±6.2 Ma for the Dongbao gneissic granite, and 441.9±3.1 Ma for the Jinxi K-granite, respectively, corresponding to Silurian Llandovery. Several xenocrysts yielded U-Pb ages around 700 Ma, implying that a breakup event took place during Neoproterozoic in the South China Block. In situ Lu-Hf isotopic analysis shows that all ɛ( t) values of zircons are negative and have two-stage Hf model ages (TDM2) from 1.4 to 3.6 Ga, indicating that the Silurian granitic magma came from the recycle of Meso-Paleoproterozoic basement and even partly Archean rocks, and had not been effected by mantle magma. Researches on regional geology suggest that an intracontinental tectono-magmatic event took place during the early Paleozoic in the study areas, which is characterized by folding and thrusting, leading to crustal shortening and thickening, up to 20 km thickness. The high geothermal temperature from thickening crust and accumulation of producing high-heat radioactive elements gradually softened crustal rocks and caused a partial melting, forming peraluminous granitic magma. Under the post-orogenic extensional and de-pressure condition, these granitic magma rose and was emplaced in the upper crust, leading to development of S-type plutons [ABSTRACT FROM AUTHOR]

Very few studies deal with the biogeochemical behaviors of rare earth elements (REEs) in goldfields. This paper presents the geochemical and biogeochemical characteristics of REEs within the soil-plant system in the Hetai goldfield, Guangdong, China. The samples from the goldfield region show anomalies in distribution patterns and behavioral characteristics of REES as compared with those from the background areas. The REEs in rocks, soils, and plants prove to be much higher than those in the surrounding regions. The distribution patterns of REEs are characterized by LREE-enrichment and HREE-depletion, with the REE concentrations in Layer A being the highest. Differentiations between LREEs and HREEs may lead to some extent of negative Eu anomaly in the soils. Research results demonstrate that the REEs in a soil profile can be transferred and accumulated during the mineral formation and supergenic geochemical processes, and the anomalies are obviously related to the geological settings for the REE-bearing ore-forming processes and to the geochemical characteristics of the habitats for the REE-bearing plants. For Dicranopteris dichotoma, the total amount of REEs in the tissues shows an order of leaf > root > stem, while for Pinus massoniana the order becomes root > leaf > stem. The distribution patterns of REEs in Pinus massoniana leaves are similar to those in soils where the plants grow up in the mineralization area. However, in the background areas the REE distribution patterns for Pinus massoniana stems are similar to those for soils where the plants grow up. Parameters such as biological absorption coefficients and biological transfer coefficients show the differences in REE absorption features among plants and indicate that REEs can be transferred among plant organs. The two coefficients can reveal the different survival mechanisms for the two plant species, which are subject to long-term REE-affected stress conditions in the gold mineralization zone. [ABSTRACT FROM AUTHOR]

Marine strata are widely exposed in the Hushan and Chaohu areas, Lower Yangtze region. As biomarker geochemistry of the strata has not been well documented, this paper deals with the biomarker composition of representative samples collected from the Silurian, Carboniferous and Triassic systems and their geological implications, thus providing clues to marine organic matter. On the basis of experimental results, it is shown that abundant biomarkers (e.g. n-alkanes, isoprenoids, terpanes and steranes) were detected. As organic matter in the strata is highly to over mature in general based on petrologic microobservation, some biomarkers (mainly n-alkanes) except terpanes and steranes cannot reflect the source, depositional environment and maturity of organic matter. Thus, primarily based on analyses of the terpanes and steranes, it is suggested that organic matter in the Silurian and Carboniferous strata is derived mainly from lower organisms, while higher plants are predominant in the Triassic organic matter. This further indicates that the depositional environment may have transformed from the marine to continental facies in the Late Triassic. These results provide new evidence for the study of regional depositional evolution, and have enriched the study of biological composition of organic matter. In addition, the biomarker geochemistry of organic matter at high to over maturation stage is addressed. [ABSTRACT FROM AUTHOR]

Abstract: Principal component analysis (PCA) is frequently used in geosciences for information extraction. In many applications, masking PCA has been used to create subsets of samples or sub-areas to enhance the effect of the main objects of interest. In this paper we suggest how the representativeness of samples or pixels can be quantified using a fuzzy membership function based on fuzzy set theory. In this new method, the relative importance of pixels or samples can be taken into account using a multivariate statistical method such as PCA. A Fuzzy Masking PCA is proposed and implemented in GeoDAS GIS on the basis of a spatially weighted PCA (SWPCA). This paper introduces the mathematical treatment of the fuzzy masking PCA and follows a case study of identifying the locations of intrusive bodies from geochemical data in the Gejiu mineral district in Yunnan, China. Power-law functions based on the inverse distance from mapped felsic intrusions are applied as weighting functions in FMPCA. The results indicate that fuzzy mask PCA increases the signal-noise ratio of the component representing igneous intrusions and decreases the influence of sedimentary rocks. The areas delineated as potential areas for new intrusions (including buried intrusions) are valuable guides for Sn mineral prospecting. [Copyright &y& Elsevier]

In this paper, with the application of satellite thermal infrared remote sensing technique, nine land surface temperature distribution maps of Changbaishan Tianchi volcano area are retrieved from nine thermal infrared images which are taken from 1999 to 2008. In terms of NDVI (Normalized Difference Vegetation Index), we classify the surface cover of the study area into three types, i.e. vegetation (forest), mixture of soil and vegetation (short grasses), and bare rock. The average temperature of each type of surface covers is calculated first, and then the average daily temperature record from Tianchi meteorological station is subtracted in order to reduce the effect of weather variation. Finally, thermal anomalies of three types of surface cover in Changbaishan Tianchi volcano area in the period of 1999 to 2008 are obtained, which is believed to reflect the magmatic activity in the magma chamber under Tianchi volcano caldera. Our results indicate that temperature of the study area increased with an intermittent tendency during 1999 to 2005, but dropped after 2005, and then maintained a relatively stable state from 2006 to 2008. Such a tendency of annual temperature variation possibly caused by magmatic activity is correlated with the results observed by means of seismic monitoring, ground deformation from GPS measurement, and volcanic gas geochemistry monitoring in the same area. It is implied that the upward intrusion of magma may cause temperature increase, and such temperature variation is great enough so that could be detected by using satellite thermal infrared remote sensing technology. [ABSTRACT FROM AUTHOR]

This paper undertook the C and N stable isotopic analysis of human bones unearthed at the Gouwan site in Xichuan, Henan, to reveal the human diets and to explore the lifestyle of humans and the development of rice and millet agriculture. The contribution of rice to human diets was almost equal to that of millet in this site though millet agriculture is the traditional economic model for the middle Yellow River Valley. On the other hand, the comparison of C and N stable isotopes in different cultural periods clearly indicates changes in millet and rice agriculture. Humans mainly depended on agriculture and gathering in the Yangshao Culture I. Millet agriculture, livestock rearing, and fishing were enhanced in the Yangshao Culture II. Millet agriculture and animal husbandry developed steadily in the Yangshao Culture III. After that the mixed rice and millet agriculture developed further. In addition, rice agriculture spread to the north in the climate suitable for cultural exchanges between north and south in the Yangshao Culture phases. In the Qujialing Culture period, under a colder climate, the rice farming was not dominant, though the Qujialing Culture played a key role in the site. [ABSTRACT FROM AUTHOR]

The Talisayi Formation found in the Guozigou region on the southern side of Sayram Lake of Xinjiang, China is a Neoproterozoic glacigenic diamictite succession that has not been adequately researched. According to its isotopic geochronology and regional stratigraphic correlation, the Talisayi Formation is equivalent to the Ediacaran glacial sediments. The present paper provides the geochemical data of the Talisayi Formation that reveals the tectonic setting and sedimentary environment in this area during the Ediacaran period. The oxides of Si, K, Na and Al and their ratios of matrix materials from glacigenic diamictites and bulk rock of siltstone and argillaceous siltstones indicate that the sedimentary environment of this formation evolved from a tectonically active region to a passive continental margin. Values of CIA (carbonate-corrected Chemical Index of Alteration) ranging from 54 to 74 show a low-middle weathering action under a glacial environment. Total organic carbon (TOC), V/Cr, Ni/Co and U/Th ratios suggest that the sediments deposited in shallow water with an oxic and weak hydrodynamic condition. There is an abrupt rise in TOC, V/Cr, Ni/Co and U/Th ratios respectively in the overlying Lower Cambrian dolomitic limestones and in the bottom of Talisayi Formation, indicating a rapidl increase in biologic productivity and a variation in redox conditions, which was probably caused by seawater mixing of deep anoxic water and surface oxic water. [ABSTRACT FROM AUTHOR]

Based on the analysis of major-element compositions of detrital sediments from the Taklamakan Desert of northwestern China, this paper aims to study chemical weathering in a hyper-arid desert environment. The major-element compositions are basically similar to the Upper Continental Crust but show a clear enrichment of CaO and depletion of Na2O and K2O, indicating the enrichment of carbonates and the decomposition of sodium and potassium silicates. The indexes of chemical alteration are relatively low and correlate negatively with the content of Na2O, implying that the degree of chemical weathering is weak and mainly controlled by the weathering of sodium feldspars. An A-CN-K model demonstrates that the detrital sediments from the Taklamakan Desert have a high homogeneity in the trend of chemical weathering. They are weathered less than sands and soil in many other Chinese deserts, and also less than similar detrital sediments in many other countries. This evidence suggests a low degree of mineralogical maturity in the Taklamakan Desert. The aeolian sediments of different ages have similar indexes of chemical weathering, suggesting that the degree of chemical weathering was consistent in the Taklamakan Desert throughout the period of aeolian deposition. The low degree of chemical weathering is caused principally by extreme aridity, rapid rejuvenation of detrital sediments associated with strong aeolian processes, and an intensive input of fluvial deposits, as well as a lack of vegetation. Due to the high concentration of erodible minerals, the desert is quite vulnerable to soil erosion and land degradation. [ABSTRACT FROM AUTHOR]

This introduction outlines the papers collected in the special issue "Evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys." The papers focus on scientific issues from Paleozoic to Cenozoic evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys concerning tectonics, petrology, geochemistry, geochronology and mineral deposits. An evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys is briefly introduced. [ABSTRACT FROM AUTHOR]

The Baimazhai nickel deposit, Yunnan Province, China, is located in the southern part of the Sanjiang (Tri-river) alkali-rich intrusive rock belt (Sanjiang ARIR). In this paper was conducted 40Ar-39Ar dating of two phlogopites in lamprophyres which are, as dikes, widely distributed in the orefield, and two plateau ages were acquired, i.e., 32.46±0.62 Ma and 32.01±0.60 Ma, respectively (averaging 32.23±0.60 Ma). The ages are obviously younger than those of the ore-hosted complex and mineralization of the Baimazhai nickel deposit. In combination with the characteristics, it is indicated that lamprophyres in the orefield and those in the Sanjiang ARIR are similar in tectonic setting, mineral assemblage and geochemistry. It is considered that lamprophyres in the orefield are the important component of the Sanjiang ARIR, and the lamprophyres and ore-hosted complex in the orefield represent the products of two times of different magmatic activity from different mantle sources. On the other hand, the age of lamprophyres in the orefield is older than that of the strike-slip shearing of the Ailaoshan-Honghe fault belt, suggesting that the strike-slip shearing of the Ailaoshan-Honghe fault belt is not the factor leading to magmatic activity of lamprophyres in the orefield, while it is more possible that magmatic activity of the Sanjiang ARIR promoted strike-slip shearing of the fault belt. [ABSTRACT FROM AUTHOR]

Middle Neoproterozoic igneous rocks are widespread in South China, but their petrogenesis and tectonic implications are still highly controversial. The Guangfeng middle Neoproterozoic volcani-sedimentary succession was developed on a rare Sibaoan metamorphic basement (the Tianli Schists) in the southeastern Yangtze Block, South China. This paper reports geochronological, geochemical and Nd isotopic data for the volcanic rocks in this succession. The volcanic rocks consist of alkaline basalts, andesites and peraluminous rhyolites. SHRIMP U-Pb zircon age determinations indicate that they were erupted at 827 ± 14 Ma, coeval with a widespread episode of anorogenic magmatism in South China. Despite showing Nb-Ta depletion relative to La and Th, the alkaline basalts are characterized by highly positive ϵNd(T) values (+3.1 to +6.0), relatively high TiO2 and Nb contents and high Zr/Y and super-chondritic Nb/Ta ratios, suggesting their derivation from a slab melt-metasomatized subcontinental lithospheric mantle source in an intracontinental rifling setting. The andesites have significantly negative ϵNd(T) values (-9.3 to -11.1) and a wide range of SiO2 contents (57.6-65.6 %). They were likely generated by the mixing of fractionated basaltic melts with felsic melts derived from the Archaean metasedimentary rocks in the middle to lower crust. The rhyolites are highly siliceous and peraluminous. They are characterized by depletion in Nb, Ta, Sr, P and Ti and relatively high ϵNd(T) values (-3.0 to -4.8), broadly similar to those of the adjacent c. 820 Ma peraluminous granitoids derived from the Mesoproterozoic to earliest Neoproterozoic sedimentary source at relatively shallow levels. We conclude that the Guangfeng volcanic suite is a magmatic response of variant levels of continental lithosphere (including lithospheric mantle and the lower-middle to upper crust) to the middle Neoproterozoic intracontinental rifling possibly caused by mantle plume activity. [ABSTRACT FROM AUTHOR]

In the future time the exploration of marine oil and gas will be one of the significant domains in China. In this paper the biomarker assemblage characteristics of oilshow in the Nanlinghu Formation of the Majiashan profile, which is located in Chaoxian County, south of Anhui Province, are described in the light of gas chromatography/mass spectrometric (GCMS) analysis on the qualitative and quantitative basis. Based on the investigation of the biomarker assemblage characteristics of possible source rocks developed in the area studied, a conclusion is drawn that the oilshow was generated from the Nanlinghu Formation source rocks (abbreviated as T1 n), instead of the Qixia Formation source rocks (abbreviated as P1 q). It is pointed out that the T1 n is of strong potential for future oil exploration, and therefore much attention should be paid to it. [ABSTRACT FROM AUTHOR]

Combined with oil and gas transport and accumulation, structure-lithology evolution history, and with geochemistry and synthesizing geology methods, this paper studies the oil and gas discharge history of Puguang large scale gas field and the main controlling factors of oil accumulation. The natural gas in Puguang gas field is mainly coal-derived gas and oil-racked gas. The main hydrocarbon is Upper Permian coal mudstone and Lower Silurian mud shale with organic material. Puguang gas field has gone through discharge and adjustment 3 times, and it has favorable palaeostructure location, high quality dredge and effectively conserving conditions. [ABSTRACT FROM AUTHOR]