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Key aspects of non-traditional isotope analysis BAI Jianghao, LIU Fang, ZHANG Zhaofeng, AN Yajun, LI Xin, XUE Yongli, XU Yuming 2020, 27(3): 1-13.  DOI: 10.13745/j.esf.sf.2020.4.7 Abstract ( 450 )   HTML ( 6 )   PDF (3061KB) ( 401 )   High-precision and high-quality analytical technique is the foundation of exploring applications of non-traditional stable isotope geochemistry. Actually, isotopic analysis is a process that the real isotopic information concealed in the sample is continuously being extracted, consisting of four basic steps, namely, sample preparation, chemical separation, mass spectrometry and data processing. In the process of isotopic analysis, each step could possibly introduce blank or contamination, and occur isotopic fractionation, which will result into mistaken information. In order to obtain the true isotopic composition of the sample, it is important to avoid contamination effectively and correct interference accurately. In this paper, on the basis of previous works, we take calcium isotope as an example, to discuss the key aspects involved in the four steps. We hope that this paper will help researchers to establish analytical methods in new isotopic systems, and also provide support in reservoir prospecting, mechanism deduction and geological applications. Figures and Tables | References | Related Articles | Metrics

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Experimental and theoretical understanding of boron isotope fractionation and advances in ore deposit geochemistry study LI Yinchuan, DONG Ge, LEI Fang, WEI Haizhen 2020, 27(3): 14-28.  DOI: 10.13745/j.esf.sf.2020.4.43 Abstract ( 435 )   HTML ( 9 )   PDF (2149KB) ( 344 )   Boron is a moderately volatile element with two stable isotopes 11B and 10B. As much as 10% relative mass difference between the two isotopes leads to significant variation in boron isotopic composition from -70‰ to +75‰ in nature. Boron is always bound to oxygen forming tetrahedral (BO4) and trigonal (BO3) coordination structures. The isotope fractionation between10B and 11B is mainly controlled by their partition between the two structures. In this study, we gave a comprehensive review on the advances in equilibrium fractionation of boron isotopes in various processes. In solution, the boron isotope fractionation factor between B(OH)3 and ${B(OH)^{-}_{4}}$ (α3-4) is controlled by pH and thermodynamic p-T conditions. At ambient conditions, the α3-4 values ranged from 1.0194 to 1.0333 by experimental and theoretical approaches. In addition to p-T-pH controls, boron isotope fractionation, caused by mineral surface adsorption between minerals (carbonates, clay minerals (montmorillonite and illite), goethite, hydromanganese, borate, etc.) and solution, is significant at low temperature. In medium and high temperature processes, boron isotope fractionation during illitization of smectite, tourmaline and muscovite minerals and in hydrothermal fluids or silicate melts and fluids are controlled by boron coordination, chemical composition, and physicochemical conditions. With further understanding of boron isotope fractionation mechanisms in individual process and isotopic distribution in various geological reservoirs, boron isotopes may be considered as sensitive indices for tracing ore-forming material sources, exploring ore-forming processes and genesis models, as well as reconstructing physicochemical conditions during ore formation. To better constrain geological concerns using boron isotopes in ore deposit geochemistry, the remaining challenges are to achieve fine characterizations of boron coordination and isotopic compositions in different host phases, such as fluids, minerals and melts. Figures and Tables | References | Related Articles | Metrics

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Advances in stable chlorine isotope geochemistry LIU Xi, WANG Yijing, WEI Haizhen 2020, 27(3): 29-41.  DOI: 10.13745/j.esf.sf.2020.4.10 Abstract ( 287 )   HTML ( 10 )   PDF (2420KB) ( 402 )   Halogen elements are relatively rare on earth and chlorine is the most abundant one. Chlorine is a strongly hydrophilic volatile element having two stable isotopes 35Cl and 37Cl with natural abundances of 75.76% and 24.24%, respectively. In this work, we reviewed chlorine isotope geochemistry, including distribution of chlorine isotopes in various geological reservoirs, factors controlling equilibrium and kinetic fractionation behaviors of chlorine isotopes, and the relevant geological applications. The chlorine isotopic compositions (δ37Cl) of evaporite, seawater, igneous rock, sediment, metamorphic rock and mantle are -0.5‰ to +0.8‰, 0.00±0.05‰, -1.12‰ to +0.79‰, -3.0‰ to +2.0‰, -3.6‰ to 0 and -1.9‰ to +7.2‰, respectively. The chlorine isotopic compositions (δ37Cl) of Moon, Mars and other planets (4-Veata) are -4‰ to +81.1‰, -5.6‰ to +8.6‰ and -3.8‰ to +7.7‰, respectively. Compared to the relatively narrow δ37Cl range (-14‰ to +16‰) on Earth, larger δ37Cl variations (-5.6‰ to +81‰) are on the Moon and Mars, indicating dramatic differences in controlling mechanisms of chlorine isotope fractionation in terrestrial and extra-terrestrial processes. In nature, chlorine isotope fractionation is mainly controlled by physical (diffusion, ion filtration, salt precipitation, volcanic systems, etc.) and chemical (water-rock interaction, metamorphism, especially in serpentinization) processes. Heavy isotopes are enriched by diffusion, ion filtration and volcanism, and δ37Cl first decreases and then increases during consecutive precipitation of salts from brine, while various factors influence the serpentine process. In combination with other geochemical indices, chlorine isotopes show great potentials in addressing a variety of geochemical issues, including prospecting for potash deposits, evaluating evolution paths of groundwater, tracing pollutant sources and quantifying bioremediation, tracking genesis of ore-forming fluid, as well as constraining planetary evolution and magma ocean degassing, and so on. Figures and Tables | References | Related Articles | Metrics

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Advances in chlorine isotope geochemistry ZHOU Qiushi, WANG Rui 2020, 27(3): 42-67.  DOI: 10.13745/j.esf.sf.2020.5.56 Abstract ( 1505 )   HTML ( 29 )   PDF (4286KB) ( 528 )   As the most representative and the most abundant halogen on the earth, chlorine has gained high attention due to its significant properties and remarkable distribution among reservoirs. Chlorine's chalcophile and volatile (incompatible) nature are significant and affect its geochemical behavior and distribution. 35Cl and 37Cl are the two stable isotopes of chlorine, their isotope abundances are respectively 75.76% and 24.24%. The stable isotope composition is reported as δ 37Cl. The commonest and the most traditional analytical method in modern chlorine isotope research is IRMS, it is highlighted by better precision compared to other analytical methods, though there are some defects such as the demand for a large sample mass and slow processing. Other analytical methods include TIMS, SIMS, LA-ICP-MS, their employment in Cl isotope analysis is still under development and not mature enough for geological application. A chlorine isotope standard commonly accepted by worldwide researchers is present and known as the Standard Mean Ocean Chloride (SMOC) proposed by Kaufmann. Its outstanding advantages include handy to collect, stable in analysis, and excellent in reproducibility. On the macroscale, the major reservoirs of chlorine on the earth can be divided into the mantle, continental crust, oceanic crust, and oceans. The mantle is undoubtedly a major reservoir due to its volume, yet we are still unable to acquire a clear result of the exact chlorine concentration constrained by our limited approaches to investigate it. The same situation applies to the Cl isotope composition of the mantle as well, in which all kinds of processes may bring about changes to Cl isotope composition. Continental crust can be further divided into sediments and its pore water, evaporites, and silicate lithosphere. Many low δ 37Cl values were observed in pore water in previous research and were generally interpreted as the result of kinetic fractionation. Large variation of δ 37Cl exists among evaporites depending on the different kinds of chloride species; although silicate lithosphere is light in chlorine contents, an observation is made suggesting the apatite Cl isotope composition varies as a function of the host rock lithology, which may be a good indicator of hydrothermal fluid activities. The oceanic crust can also be further divided into sediments and pore water, evaporite, and additionally altered oceanic crust (AOC). The altered hydrous minerals (amphibole, serpentine, etc.) are featured by a heavy δ 37Cl value and may have something to do with the oxidation states of metal cations. The oceans are together a massive chlorine reservoir as well, the stability of their Cl isotope composition has already been approved by many studies. In addition to all the mentioned reservoirs, Cl isotope analysis is applied to extraterrestrial samples such as meteorites, lunar rocks, and atmosphere as well. Generally, the mechanisms of Cl fractionation can be divided into equilibrium fractionation and kinetic fractionation. Factors controlling equilibrium fractionation include the valence state of chlorine itself, the metal cation it bonds with, and the difference of chloride species in a solid-aqueous phase equilibrium system. Processes of kinetic fractionation include diffusion, ion filtration, and activities in the magma degassing system. Ever since the two stable isotopes of chlorine got discovered about 100 years ago, geochemical methods related to chlorine isotopes have been applied to all branches of geology. For example, chlorine isotopes can be used to trace the sources of formation water in hydrogeology, or contaminants in environmental geology; chlorine isotopes can also be used to track deposit formation in economic geology or interpret the evolution process of the earth in planetary geology. Attempts and explorations are continuously conducted using chlorine isotopes. However, constrained by our knowledge of the actual geological processes, there are still a bunch of frontier problems hindering the development of chlorine isotope research. For example, what is the key factor in early solar system processes determining the current chlorine content of the earth; what kind of evolution history caused the current volatile distribution in the earth; what is going on with respect of the volatile cycling; what is the flux process between the subducting plate and mantle and so on. Figures and Tables | References | Related Articles | Metrics

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A review of titanium isotope geochemistry ZHAO Xinmiao, TANG Suohan, LI Jin, ZHU Xiangkun, WANG Hui, LI Zhihan, ZHANG Hongfu 2020, 27(3): 68-77.  DOI: 10.13745/j.esf.sf.2019.4.41 Abstract ( 478 )   HTML ( 12 )   PDF (2117KB) ( 446 )   Advances in analytical techniques lead to increasing application of non-traditional stable isotope in the investigation of high-temperature processes, such as magmatic differentiation, core formation, and early solar nebula evaporation and condensation. Although titanium (Ti) is a very important transition metal element occurring widely on Earth and other Earth-like planets, Ti stable isotope has received little attention to date. This is because Ti is relatively insoluble in sub-critical aqueous fluids and is highly refractory, i.e., resistant to later modification or resetting by metamorphism or alteration. Its isotopic variations have seldom been measured. Recent advances in double spike technique and the development of multi-collector inductively coupled plasma (MC-ICPMS) make it possible to acquire Ti isotopes with high precision. As a result, significant fractionation of Ti stable isotope has been found in natural samples. The large fractionation has important implications for the measurement and application of Ti isotopes, with great potential in tracing various geological processes. In this review, we summarized the recent advances, important applications and future directions of Ti isotope geochemistry. We start with a brief summary on nomenclatures and analytical methods, followed by Ti isotopic compositions of chondrites and Bulk Silicate Earth (BSE), then with a summary on the magnitude and mechanisms of Ti isotopic fractionation during magmatic differentiation at high temperatures. It seems that Ti isotopes can serve as high-fidelity tracers of magmatic evolution and genesis of ancient igneous rocks and Earth's crust. Finally we highlight future work needed to advance the research and applications of Ti isotope geochemistry. Figures and Tables | References | Related Articles | Metrics

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Stable chromium isotope geochemistry WANG Xiangli, WEI Wei 2020, 27(3): 78-103.  DOI: 10.13745/j.esf.sf.2020.3.5 Abstract ( 889 )   HTML ( 51 )   PDF (4639KB) ( 512 )   With the advancement of multicollector mass spectrometry, the stable chromium isotopic system has been widely applied to solving environmental and geochemical problems. Chromium is a redox-sensitive element, and transformations between different oxidation states are accompanied by large isotopic fractionations. Therefore, chromium isotopes play important roles in investigating the redox conditions of modern and paleo-environments. Moreover, chromium is a moderately compatible and slightly siderophile element, and large isotope fractionation exists between different minerals. Thus, chromium isotopes can also be potentially applied to study mantle partial melting, magma differential crystallization, and planetary evolution. In this review, we covered the following topics: (1) an overview of chromium stable isotopic systematics; (2) analytical methods; (3) isotopic fractionation mechanisms; and (4) applications of stable chromium isotopes in high- and low-temperature geochemistry. Figures and Tables | References | Related Articles | Metrics

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Stable potassium isotope geochemistry and cosmochemistry WANG Kun, LI Weiqiang, LI Shilei 2020, 27(3): 104-122.  DOI: 10.13745/j.esf.sf.2020.4.5 Abstract ( 1345 )   HTML ( 45 )   PDF (2507KB) ( 670 )   The high-precision potassium (K) stable isotope system is one of the emerging non-traditional isotope systems enabled in recent years by the advance of Multi-Collector Inductively-Coupled-Plasma Mass-Spectrometry (MC-ICP-MS). Here we provide a brief overview on 1) the geochemical and cosmochemical properties of potassium and its major reservoirs, and the abundances of K on earth and in the rest of the Solar System; 2) the history of K isotope studies from 1922 to 2019; 3) the analytical methods of studying K isotopes including column chromatography and mass spectrometry (Thermal Ionization Mass Spectrometry-TIMS, Secondary Ion Mass Spectrometry-SIMS, and MC-ICP-MS); 4) the applications of K stable isotopes in low-temperature geochemistry and biogeochemistry, such as understanding processes of continental weathering, hydrothermal alteration, and reverse weathering; 5) the applications of K stable isotopes in high-temperature geochemistry, such as studying subduction dehydration/metamorphism, tracing subducted oceanic crustal materials and evaluating mantle heterogeneity; and 6) the applications of K stable isotopes on cosmochemistry, such as understanding solar nebular condensation, parent-body processing, planetary formation and magma ocean evolution. Figures and Tables | References | Related Articles | Metrics

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Advances in rubidium isotope analysis method and applications in geological studies ZHANG Zhuoying, MA Jinlong, ZHANG Le, ZENG Ti, LIU Ying, WEI Gangjian 2020, 27(3): 123-132.  DOI: 10.13745/j.esf.sf.2020.4.13 Abstract ( 560 )   HTML ( 11 )   PDF (1443KB) ( 346 )   Rubidium (Rb) is an alkali metal element with moderate volatility, fluid activity and high magmatic incompatibility, which is essential for tracing material provenance and providing valuable information on various geological processes. Meanwhile, 87Rb is a radioactive isotope which can decay to 87Sr with a long half-life (T1/2=4.976×1010 a). Therefore, Rb-Sr dating system has been widely used to determine geological age of long-time scale. Traditionally, Rb isotopic composition (87Rb/85Rb) of geological samples are considered constant for specific geological period. However, with advances in both Rb purification technique and Rb isotopic measurement by mass spectrometry, high-precision Rb isotopic compositions can be precisely determined. And the limited data show that geological samples can have different 87Rb/85Rb ratios due to isotopic fractionation during diverse geological processes. Questions still remain that whether Rb isotopic fractionation can provide additional clues for Rb tracing or affect precision of classical Rb-Sr dating method. To answer these questions, it is important to investigate δ 87Rb values of major geological reservoirs, discover Rb isotopic fractionation during various geological processes and explore the relevant mechanism of the fractionation systematically. Research in these areas, however, is extremely scarce to date. In this paper, we reviewed Rb isotope studies in the past 20 years, including analytical methods and fractionation mechanism, and provide our perspectives on relevant applications in the near future. The scope of our work and main findings are as follows: (1) We summarized previous studies regarding Rb chemical purification and instrumental measurement and compared the advantages and disadvantages of these techniques to show that careful chemical pretreatment and robust instrumental determination are the prerequisites for obtaining high-precision Rb isotopic ratios; (2) We compiled data on Rb isotopic compositions of extraterrestrial samples and briefly described Rb isotope application in cosmochemistry, e.g., as a moderate volatile element, Rb isotopes are promising in constraining accretion and evolution of the inner solar system; (3) Rb isotopes show potentials in solving many geological issues, such as improving classical Rb-Sr dating system, understanding differentiation process between crust and mantle, restricting continental chemical weathering processes, and advancing our understanding of Rb deposit formation. Figures and Tables | References | Related Articles | Metrics

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Space, Earth, ocean: mineralogical studies under extreme conditions SHU Jinfu 2020, 27(3): 133-153.  DOI: 10.13745/j.esf.sf.2019.12.3 Abstract ( 406 )   HTML ( 6 )   PDF (6198KB) ( 291 )   Research of the Deep Space-Earth-Sea System involves micromineral study, mineral discovery as well as mineralogical investigations under extreme conditions, e.g. research on meteorolite samples and materials in meteorite craters, minerals in deep Earth, and seafloor methane hydrates. We mainly used diamond anvil cell (DAC) simultaneously in combination with synchronous radiation X-ray and neutron sources. In addition, we used various physical, chemical and optical methods (rock mineral chemical analysis, optical measurement, electron probe, ion probe, scanning electron microscope, transmission electron microscope, infrared, ultraviolet, Raman spectroscopy, laser heating, etc.). We investigated crystal structures and physical and chemical properties of mineral materials of different compositions under different temperature and pressure conditions. In this paper, we focused on a variety of typical minerals formed from various components at extreme temperatures and pressures from the Earth's core to crust. They include ε-Fe in the metallic solid inner core and liquid outer core, post-perovskite structure (ppv) magnesium iron silicate (Mg,Fe)SiO3 in the D″ layer located at the core-mantle boundary (CMB), perovskite structure (pv) magnesium iron silicate in the lower mantle, Bridgmanite (Mg,Fe)SiO3, mafic oxide (Fe,Mg)O and post-spinel structure containing Fe3+ Maohokite (HP-MgO4), and magnesium ferrosilicate, silicon oxide, chromite, diamond and its inclusions, methane hydrate (CH4·H2O), etc., in the transition zone, upper mantle, crust and ocean bottom. The research of mineralogy under extreme conditions provides new insights into the structure and properties and dynamic evolution of the Earth. Figures and Tables | References | Related Articles | Metrics

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Zircon U-Pb dating and trace element geochemistry in syenite porphyry and granite xenoliths from Liuhe, western Yunnan, China DUAN Wenjing, ZHAO Fufeng, REN Kefa, LIU Xianfan, DENG Jianghong, YANG Mimi, CHU Yating 2020, 27(3): 154-167.  DOI: 10.13745/j.esf.sf.2020.4.44 Abstract ( 208 )   HTML ( 4 )   PDF (5488KB) ( 232 )   The Liuhe syenite porphyry is a typical representative of the Cenozoic alkali-rich porphyry in western Yunnan. It is famous for various xenoliths developed at different depths, including granite xenoliths of the same period. The deep geological processes represented by these xenoliths have important constraints on the formation and evolution of alkali-rich magma. In this paper, we focused on zircon trace element analyses, and combined with the studies on syenite porphyry main elements, zircon U-Pb dating, Ti thermometer and zircon oxygen fugacity of the Liuhe syenite porphyry and its granite xenoliths to explore the formation and evolution process of alkali-rich magma. The zircon U-Pb dating results suggested that the activity time of Liuhe alkali-rich magma is 37.89±0.96 to 35.87±0.58 Ma, almost synchronous with that of granite inclusions representing the same period of silicon-rich acidic magma at 38.21±0.44 to 36.21±0.36 Ma. The zircon trace element diagram showed that zircons from syenite porphyry mainly overlapped with the potassium-magnesium lamprophyre range, suggesting that alkali-rich magma source has mantle properties; whereas zircons from granite xenoliths overlapped in part with the granite range. The overlapping part confirmed a common growth environment during syenite porphyry and granite xenoliths zircon crystallization. The estimated Ce(Ⅳ)/Ce(Ⅲ) ratio and Ti temperature calculations showed that oxygen fugacity of the alkali-rich magma and zircon crystallization temperature changed greatly between 36.42 and 36.41 Ma, indicating the effect of mixing alkali-rich and entrapped granitic magma; while decreasing oxygen fugacity oscillation reflects magma supplement from a later mantle source. In summary, we speculate that the Himalayan alkali-rich magma from enriched mantle source in the Liuhe area underplates and melts the overlying felsic rocks to form granitic magma, and a small amount of which mix with alkali-rich magma to form syenite porphyry. Figures and Tables | References | Related Articles | Metrics

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Magmatic response to lithospheric thinning of the North China Craton: evidence from porphyritic aegirite-bearing syenite in Wu'an, Hebei, China ZHANG Bo, SU Shangguo, MO Xuanxue, FENG Shaochong, WU Yue, JIANG Xiao, FENG Yanfang, LIU Jiangtao 2020, 27(3): 168-181.  DOI: 10.13745/j.esf.sf.2019.9.24 Abstract ( 245 )   HTML ( 2 )   PDF (4199KB) ( 207 )   The Hongshan alkaline complex is located in the southern section of the Taihang Mountains, Hebei Province with an outcrop area of about 53 km2. Its lithology is dominated by syenite and intruded in the Late Paleozoic-Mesozoic strata. Our study showed that the alkaline intrusive complex belongs to alkaline series, formed in an extensional environment at the age of 120.1±4.6 Ma as a product of the peak period of the North China Craton magmatism. The REE patterns showed no Eu anomaly. The complex is enriched in light rare earth and large ion lithophile elements, such as Rb, K, Sr, and depleted in high field strength elements, such as Nb, Ta and Ti, exhibiting continental crustal characteristics. We observed in the field that the rocks are characterized by deep and shallow-ultra shallow formation. We also observed through electron microprobe analysis that the feldspar has a reverse belt that contained no inherited zircon. These observations, combined with the notion that partial melting of Earth's crust is needed to produce syenitic magma without Eu abnormalities, suggested a formation pressure of greater than 20 kbar. That is, the Hongshan syenite formed by partial melting of the thickened crust with some mantle derived magma mixing and mantle fluid injection to produce its mantle Hf and Nd isotopic signatures without altering the major and trace elemental characteristics, and then rose rapidly to the Earth surface under extensional condition. Figures and Tables | References | Related Articles | Metrics

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Geochemical characteristics and sedimentary environments of siliceous in the middle and western parts of the Shiquanhe-Yongzhu-Jiali tectonic belt XU Mengjing, ZHAO Peiyun, LAN Rui, WU Yanwang, XIAO Xue, ZHANG Jinbo 2020, 27(3): 182-190.  DOI: 10.13745/j.esf.sf.2020.4.1 Abstract ( 181 )   HTML ( 4 )   PDF (2110KB) ( 249 )   The geochemistry of radiolarian siliceous, as sedimentary cover of ophiolite, plays a role in investigating the formation environment of ophiolite and tectonic-paleogeographic evolution of the sedimentary basin. In this paper, we studied the petrology and whole-rock geochemistry of Guchang siliceous in the western part of the Shiquanhe-Yongzhu-Jiali tectonic belt (SYJTB), and carried out a comparative analysis involving Laguoco and Guomangco siliceous to determine the origin and sedimentary environments of siliceous in these areas. The low SiO2 content and Al/(Al+Fe+Mn) ratio (0.87-0.95) indicate a non-hydrothermal origin of Guchang siliceous. The rare earth element (REE) patterns of most of these rocks show left-leaning types with slight light REE (LREE) and obvious Eu depletion and no Ce anomalies. The Y/Ho, Ti/V and V/Y ratios in Guchang siliceous are 21-24, 220.67-862.02 and 0.05-0.29, respectively. These results suggest that Guchang siliceous is formed in a continental margin environment. The characteristics of Laguoco and Guchang siliceous were similar. However, Guomangco siliceous has some oceanic basin siliceous characteristics affected slightly by hydrothermal fluids, indicating its probable formation in a more mature oceanic basin. Combining with the ophiolite data, the middle and western part of the SYJTB likely represent an ancient oceanic basin near the continental margin, and the oceanic basin in Guomangco is more mature and wider than that those in Guchang and Laguoco. Figures and Tables | References | Related Articles | Metrics

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Garnet trace elemental geochemistry and its application in sedimentary provenance analysis HONG Dongming, JIAN Xing, HUANG Xin, ZHANG Wei, MA Jinge 2020, 27(3): 191-201.  DOI: 10.13745/j.esf.sf.2020.1.1 Abstract ( 388 )   HTML ( 8 )   PDF (3133KB) ( 285 )   Garnet is a common heavy mineral in sediments. It can come from a variety of rocks and shows a variety of geochemistry compositions in different parent-rocks. Therefore, geochemical analysis of detrital garnet is widely used in sedimentary provenance research. The elemental geochemistry of single detrital mineral is easily obtained by electron microprobe and applied to the provenance analysis. However, there are certain limitations. For instance, the major elemental compositions of garnet in both intermediate-acid igneous rocks and metasedimentary rocks are usually characterized by high Fe and Mn. Here, we systematically investigated trace elemental geochemical data of garnet from different types of rocks and attempted establishing some useful trace elemental proxies for detrital garnet provenance analysis. The main conclusions are: (1) Rare earth elements and yttrium can be employed to distinguish detrital garnets from intermediate-acid igneous and metasedimentary rocks; (2) Garnets from basic rocks (peridotite, pyroxenite) and the corresponding meta-basic rocks (eclogite) had fairly consistent major and trace elemental geochemistry, but some garnets from peridotite rocks had unique praseodymium/holmium (PrN/HoN) values and total heavy rare earth elements (ΣHREE), which can be applied to sedimentary provenance analysis with basic rock-dominanted backgrounds; (3) Garnet in skarn was characterized by overwhelmingly high Ca, but rare earth element compositions were diverse, which can be interpreted as magma type (indicating rich iron and oxidation environment) or contact metasomatic type (reflecting rich aluminum and reducing environment). Collectively, the trace elemental geochemistry of garnet can be effectively used in sedimentary provenance analysis, which is an important supplement to the major element-based provenance analysis. Figures and Tables | References | Related Articles | Metrics

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Background values of 69 elements in catchment sediments of the China-Mongolia boundary region LIU Hanliang, NIE Lanshi, SHOJIN Davaa, WANG Xueqiu, CHI Qinghua 2020, 27(3): 202-221.  DOI: 10.13745/j.esf.sf.2020.4.4 Abstract ( 243 )   HTML ( 4 )   PDF (11258KB) ( 188 )   The Sino-Mongolian border area has excellent ore-forming geological conditions and is one of the world's important metal mineralization provinces and one of the world's three major porphyry copper (gold and molybdenum) metallogenic belts. We collected a large amount of geochemical data from the Sino-Mongolian cooperation project on a geochemical mapping at 1∶1000000 scale, which provides basic data for the study of elemental dispersion and enrichment, mineralization trends, resource evaluation and environmental changes in the border area, and also supports decision making in resource layout for the ‘One Belt One Road’. We calculated background values of 69 elements in catchment sediments based on the mapping data across the China-Mongolia boundary. We used the median values of the dataset (using 3-sigma control limits) as the estimated geochemical background values. The results showed that different geological backgrounds led to different geochemical distribution patterns, and different tectonic units had significantly different geochemical characteristics. The massive elemental accumulation provides sufficient elemental supply to forming large deposits of specific geochemical province. These background values can be used as the basic reference data for comparing further development and utilization of geochemical mapping data across the China-Mongolia boundary. Figures and Tables | References | Related Articles | Metrics

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Discovery of the Silurian andesitic porphyry in the Xiaohulishan Mo-polymetallic deposit, the Beishan district, Inner Mongolia, and its geological significance ZHANG Dayu, FU Xiang, WEI Ouxiang, YE Longxiang, JIANG Hua, ZHANG Yong, XIN Houtian 2020, 27(3): 222-238.  DOI: 10.13745/j.esf.sf.2020.4.25 Abstract ( 171 )   HTML ( 5 )   PDF (5588KB) ( 170 )   The Xiaohulishan Mo polymetallic deposit is located in the northeastern part of the Beishan district, Inner Mongolia, in which the Ordovician Xianshuihu Formation volcanic rocks occur. In this study, the authors discovered andesitic porphyry intruding into the andesite as stocks during the ore-bearing volcanic rock section observation. The zircon LA-ICP-MS U-Pb dating result of the andesitic porphyry is 419±5 Ma, corresponding to Late Silurian epoch and much younger than the Ordovician andesite 489±11 Ma. The dating results rectify the viewpoint that there are only Ordovician volcanic rocks distributing in the Xiaohulishan deposit. The geochemical characteristics of the Silurian andesitic porphyry in the Xiaohulishan deposit show that the SiO2 contents are between 57.18% and 58.19%, the K2O+Na2O contents are between 5.78% and 6.97%, and the TiO2 contents are between 0.57% and 0.90%, which indicate the andesitic porphyry is K-Al-rich, Na-poor rocks, and obviously different from the Ordovician low calc-alkaline andesite. The Silurian andesitic porphyry exhibits enriched in LILE (e.g. Rb, Ba, U, K, and Sr), but depleted HFSE (e.g. Nb, Ta, and Ti). The ∑REE concentrations of the andesitic porphyry are from 71.9×10-6 to 72.24×10-6, which is lower than andesite (96.89×10-6). The LREE/HREE ratio of Silurian andesitic porphyry is from 4.68 to 5.91, showing a weak right-leaning trend with weak negative Eu anomalies, which probably experienced lower degree differentiation than andesite. The Silurian andesitic porphyry in the Xiaohulishan deposit is derived from crust-mantle mixing zone, and underwent weak differentiation and contamination during its emplacement. Based on regional geological setting, geochronology, and geochemical characteristics, it is showed that the Beishan district, Inner Mongolia underwent same geological evolution during the Early Paleozoic era, which probably consistently belongs to the island-arc accretion zone between the Siberia and the Tarim plates. Figures and Tables | References | Related Articles | Metrics

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Fluid evolution of iron oxide-Cu-Au (IOCG) deposits in the basin inversion setting, North Xinjiang: constraints from halogen and noble gas composition of fluid inclusions LIANG Pei, CHEN Huayong, ZHAO Liandang, Kendrick MARK, JIANG Hongjun, ZHANG Weifeng, WU Chao, XIE Yuling 2020, 27(3): 239-253.  DOI: 10.13745/j.esf.sf.2020.4.3 Abstract ( 171 )   HTML ( 5 )   PDF (3296KB) ( 137 )   Represented by the Laoshankou, Qiaoxiahala and Heijianshan deposits, the northern margin of East Junggar and the Yamansu belt of East Tianshan are two important potential belts for iron oxide Cu-Au (IOCG) mineralization in North Xinjiang. All IOCG deposits in these two regions formed in a basin inversion setting and show significant two-stage mineralization. In this study, we used halogen and noble gases as reliable tracers to track the fluid sources and evolution of these deposits. The results showed that three different fluid end members are mainly involved in the mineralization processes of the three deposits: (1) the magmatic hydrothermal fluid, with I/Cl, Br/Cl and 40Ar/36Ar ratios of (16.3-18.0)×10-6, (1.03-1.06)×10-3 and 352-437, respectively, in the magnetite stage of the Heijianshan deposit; (2) surface-derived basin brine by seawater evaporation, with I/Cl, Br/Cl and 40Ar/36Ar ratios of (77.1-87.7)×10-6, (1.53-1.80)×10-3and 672-883, respectively, in the copper-gold stage of the Laoshankou deposit; and (3) basin brine or formation water by water-rocks reaction and evaporate dissolution, with I/Cl, Br/Cl and 40Ar/36Ar ratios of (477-26 301)×10-6, (0.39-1.28)×10-3and 288-510, respectively, as the main mineralizing fluids in the magnetite stage of the Laoshankou and Qiaoxiahala deposits and for the Cu-Au mineralization of the Qiaoxiahala and Heijianshan deposits. The obvious multi-stage mineralization and involvement of Ca-rich hypersaline non-magmatic brines in the Cu-Au stage in the iron oxide Cu-Au deposits in North Xinjiang resemble the characteristics of other IOCG type deposits in the world. Figures and Tables | References | Related Articles | Metrics

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Rheology of the lower crust controls the polarity of conjugated basins asymmetry on the South Atlantic passive margin WANG Dianju, LI Jianghai, LI Yihe 2020, 27(3): 254-261.  DOI: 10.13745/j.esf.sf.2020.4.2 Abstract ( 183 )   HTML ( 4 )   PDF (2301KB) ( 142 )   The passive continental margin basins on both sides of the South Atlantic contain a large amount of oil and gas resources and became an important target for oil and gas exploration in recent years. The conjugated basins of the South Atlantic passive margin has clear asymmetry, such that the width of the Santos Basin (~850 km) on the South American side is four times that of the South Kwanza Basin (~200 km) on the African side. Basin structural asymmetry leads to significant differences in oil and gas distribution and accumulation. However, the dynamics of this asymmetrical structure is still controversial. Here, we carried out a series of 2D thermodynamic numerical modeling experiments, using finite element method to solve the constitutive equation of the visco-elastic-plastic continuous medium. The results showed that the rheology of the lower crust is the key factor controlling the structure of the basin. When the rheology of the lower crust is asymmetrical, basins developed on the craton are narrower than those on the orogenic fold belts. The deep crust of the craton alters the flow of the asthenosphere, thus controls crustal rupture and basin structure. Compared to the previous modeling results, our model can predict not only the formation process of asymmetric basins, but also the polarity of the conjugated basins to better match the geological conditions of the South Atlantic. Figures and Tables | References | Related Articles | Metrics

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Quantitative study of shallow natural gas source in tunnels in the Longquanshan structural zone ZHANG Xiaolin, SU Peidong, SU Shaofan, MA Yunchang, YANG Feng 2020, 27(3): 262-268.  DOI: 10.13745/j.esf.sf.2020.4.8 Abstract ( 142 )   HTML ( 2 )   PDF (1785KB) ( 121 )   The Longquanshan oil-bearing structural belt is at the boundary between the western and central Sichuan oil and gas fields. Its non-coal strata are mainly Jurassic and Cretaceous red layers producing no hydrocarbons. Yet tunnel constructions across the Longquanshan tectonic belt are often confronted with shallow gas hazard. To ascertain the source of shallow natural gas and provide more accurate prediction on gas distribution characteristics in the non-coal strata tunnels, we studied the Chengdu Metro Line 18 Longquanshan Tunnel as an example, using field composition testing, gas chromatography and stable carbon isotopes to quantitatively characterize the source of shallow natural gas in the area. Previous research predicted that the main components of the shallow natural gas were CH4 (57.65%-75.23%), N2, and CO2. We showed that δ13C1, δ13C2 and δ13C3 values were 40‰, 26‰ and 25‰, respectively, by stable isotopic analysis, and the age of gas source rocks was between 225 and 249 Ma from rare gas isotope experiments. Using biomarker compounds we determined the regular sterane ratio to be between 0.90 and 1.07. Large amounts of shallow natural gas, originated from the underlying Triassic Xujiahe Formation, escaped from the Longquanshan tunnel. The deep gas migrated mainly upward through faults and joint fissures. Enrichment in shallow sandstones, joint fissure development areas, and local structural highs all pose danger to tunnel engineering. The Chengdu Metro Line 18 Longquanshan Tunnel lies cross the Longquanshan petroleum structure. The absolute gas emission from the palm face of the tunnel reached 2.13-4.99 m3/min. The distribution of shallow natural gas is controlled by the Longquanyi fault, Wolongsi syncline, Longquanshan anticline, and Ma'anshan fault. The Longquanyi and Ma'anshan faults provide upward migration pathways in the deep Triassic Xujiahe Formation, where the two faults are associated with derived joint and fissure development areas, while the turning section of the Longquanshan anticline is favorable for shallow natural gas accumulation. Together these geological factors contribute to the high gas concentration and high risk for tunnel construction in the area. Figures and Tables | References | Related Articles | Metrics

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Characteristics of geothermal geology of the Wucheng uplift geothermal field WANG Di, WANG Xinwei, MAO Xiang, WU Minghui, LIU Huiying, ZHANG Xuan, WANG Tinghao 2020, 27(3): 269-280.  DOI: 10.13745/j.esf.sf.2020.3.1 Abstract ( 482 )   HTML ( 8 )   PDF (4397KB) ( 241 )   Driven by the “Xiongxian model” and environmental pressure, the Hebei Province has become the largest agglomerate of urban geothermal heating in China. Therefore, studying geothermal geological characteristics of the Wucheng uplift can be significance for guiding geothermal development in Gucheng County, Hebei Province. In this paper, we studied the distribution patterns of different types of thermal reservoirs, as well as physical properties and characteristics of geothermal water recharge and circulation pathway of the reserviors, and performed geothermal resources evaluation, by combining logging, seismic and regional geological data with results of hydrochemical characteristic and isotopic analyses. The results showed that the geothermal field has two thermal reservoirs: sandstone and karst reservoirs. The former has a wide stable distribution, with the main aquifer situated in the lower Guantao Formation and a floor depth of 1200-1600 m. The geothermal water temperatures ranged between 52-54 ℃, and the well water yield was 79-123 m 3/h. The favorable zones of karst thermal reservoir are mainly distributed in the anticlinal core of the Cambrian-Triassic, extending in a N-S zonal direction, with the main aquifer in the upper Majiagou, lower Majiagou and Liangjiashan Formations and a roof depth of 2100-2900 m. The geothermal water temperatures ranged between 82-85 ℃, and the well water yield was 75-98 m3/h. The geothermal waters originate from the recharge areas of the Taihang mountains to the west and Yanshan mountains to the north, moving horizontally along the NE-SW fracture zone and the karst unconformity plane into the shallow thermal reservoir, from where they meet in the Wucheng uplift, through the Cangxian and Xingheng uplifts, to form a medium-low temperature geothermal reservoir of Cl-Na type water quality. The 14C dating results indicated that the geothermal waters of sandstone and karst reservoirs were 21 ka and 32 ka, respectively, with a recharge depth of more than 2822.5-3032.5 m. The Minghuazhen Formation and the Carboniferous-Permian strata are cap rocks of the two thermal reservoirs, respectively. According to a fine evaluation of Wucheng geothermal resources, the total geothermal reserves amount to 4.86×1010 GJ, equivalent to 16.6×108 tons of standard coal. The annual geothermal exploitation can meet 1.1×108 m2 indoor heating demand, demonstrating a huge geothermal developmental potential in the region. Figures and Tables | References | Related Articles | Metrics

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A calculation method for assessing the social benefits of a sponge city: a case study for the Peiyang Park Campus, Tianjin University LI Mengmeng, GUO Qizhong, LIAN Jijian, CHEN Liang 2020, 27(3): 281-289.  DOI: 10.13745/j.esf.sf.2020.4.40 Abstract ( 710 )   HTML ( 17 )   PDF (2150KB) ( 214 )   The social benefits of a sponge city refer to its contribution to society such that sponge city facilities contribute far more than their direct economic benefit. However, the social benefits of a sponge city are difficult to calculate objectively, which hinders people's understanding of such cities. An objective calculation of the social benefits not only reflect whether sponge city facility constructions are cost-effective, but also provides a reference for government policy making. Therefore, we developed an objective calculation method combining subjective evaluation and objective calculation. By subjectively assessing social benefits that can be objectively calculated, the evaluation scores are used to calculate other social benefits that can only be evaluated subjectively. In this study, we tested our method on the sponge city facilities on the Tianjin University's Peiyang Park Campus. The results showed that the social benefits of sponge city facilities, including rainwater garden and wetland, recessed greenspace, vegetation buffer zone and permeable pavement, were 1.0-15.5 RMB/(m2·a), grass ditch was 2.97 RMB/(m·a). Among these facilities, rainwater wetland ranking the highest and recessed greenspace the lowest. For the Peiyang Park Campus, the total social benefits of sponge city facilities, according to the total construction area, is about 2.328 million RMB per year. Figures and Tables | References | Related Articles | Metrics