Abstract:

The Na'a deposit in Chayu County, Xizang, Southwest China, is located in the most eastern section of the Gangdis metallogenic belt, which is a typical skarn tungsten ore deposit, contains multiple generations of garnet in skarn and sulfide-carbonate altered rocks. Garnet is a representative mineral in skarn deposit. The systematic research on garnet fills the gap of previous research and provides new data. The composition characteristics and ring band changes of garnet are often used to indicate the physical and chemical properties, migration and evolution, and the metallogenic process of the fluid. According to the alteration mineral combination and interpenetration relationship in field observation and indoor identification, garnet can be divided into three types from early to late: BR type (brown red), DB type (dark brown), and B type (brown) garnet. The garnet is mainly composed of grossularite, followed by andradite. Its formation is characterized by brown-red to dark brown to brown, which is accompanied by the decrease of grossularite component and the increase of andradite and spessarite components. All three types of garnet developed typical octagon and ring band characteristics under the microscope, with the characteristics of high calcium, low manganese and low magnesium components, showing the typical hydrothermal erosion into the cause. The high grossularite content of BR and DB indicates the relative reduction of the forming environment, whereas the increasing andradite content of type B indicates the trend of fluid evolution to oxidation environment. The REE content and Fe³⁺ / (Fe³⁺ + Al³⁺) ratio are indicating the relative reduction of the overall crystallization conditions. The garnet all showed the characteristics of depleted light rare earth, enriched heavy rare earth content, negative Eu content and gradually increasing content, indicating that the metallogenic hydrothermal fluid in the skarn stage is in relatively neutral conditions. The mass-like substitution mechanism of rare earth elements is mainly ^Ⅷ+^Ⅳ→^Ⅷ+^Ⅳ及^Ⅷ+^Ⅵ→^Ⅷ+^Ⅵ. By comparing the contents of garnet W and Sn in different types of polymetallic skarn deposits, the results showed that the content of garnet W and Sn in W mineralized deposits was significantly higher than that of non-W mineralized deposits, indicating that the W and Sn content of garnet had certain indicator significance for mineralization. Furthermore, elements U and Eu can dynamically reflect the redox conditions for mineral growth, the W-U and W- δEu relationship characteristics of garnet can be used as an indicator of different types of skarn W deposits.

Abstract:

The newly discovered Dana ancient volcanic edifice in the Nanmulin area of Xizang provides a window for exploring the lithofacies composition of continental volcanic edifice and its tectonic significance. This study conducts geological profile measurements and petrographic studies on the Dana ancient volcanic edifice, and conducts zircon LA-ICP-MS U-Pb dating and the whole-rock geochemical analysis for the porphyric monzonitic granite which intrusived into volcanic channel laterly. The results show that the zircon U-Pb age of the porphyric monzonitic granite is 54.0±1.4 Ma, with high silicon (SiO₂=71.03%~75.88%), high potassium and low sodium (K₂O/Na₂O=1.45~1.79), rich alkali (ALK=8.97%~9.67%), and low titanium (TiO₂=0.17%~0.37%) characteristics. The A/CNK value ranges from 0.95 to 1.00, and the Rittman index (σ) ranges from 2.45 to 3.38, belonging to the quasi-aluminous and calc-alkaline rock series. Enrichment of light rare earth elements and relative depletion of heavy rare earth elements (LREE/HREE=7.60~9.78), with obvious differentiation characteristics, (La/Sm) _N=2.85~4.21; Large ion lithophilic elements such as Rb, Th, U (LILE) and incompatible elements are relatively enriched, while high field strength elements such as Nb, Ta, P, Ti (HFSE) are relatively depleted, exhibiting typical geochemical properties of subduction arc or crustal magmatic rocks. Based on the above geological information, it is indicated that the Dana ancient volcanic edifice was formed before 54 Ma, and the porphyric monzonitic granite was formed in the tectonic background of the active continental margin during the India-Eurasia collision. Under the action of mantle-derived magma intrusion, the middle and lower crust melted, and then the magma differentiated and ascended to infiltrate and crystallize in the volcanic channel.

Abstract:

Laoshan granites are widely distributed in Jiaodong area. Their typology, magma source and petrogenesis are still controversial, and the magmatic evolution and petrogenesis of highly fractionated I-type granite have not been well constrained. In this study, the Laoshan Early Cretaceous granites are selected as the research theme. The granites are analyzed by petrology and petrography, whole rock major and trace elements, zircon U-Pb dating and Lu-Hf isotopes, plagioclase electron probe analysis. LA-MC-ICP-MS zircon U-Pb dating results show that the diagenetic ages of quartz monzonite, monzogranite, syenogranite and granitic porphyry in Laoshan are 128.6±2.7 Ma, 122.8±2.5 Ma~118.6±1.2 Ma, 121.5±2.7 Ma~121.3±1.2 Ma and 114.5±1.2 Ma, respectively, indicating that they were all emplaced during the Early Cretaceous. The geochemical composition of Laoshan granites show high contents of silicon and alkali, low abundances of aluminum, magnesium and iron. They are also depleted in Rb, Th, U,Ba and Sr, with significant negative Eu anomaly. The zircons εHf(t) values of Laoshan granites range from -21.0 to -15.1 , and Hf isotope second-stage model ages (t_DM2) range from 2 482 to 2 149 Ma. Based on mineralogical, petrological and geochemical evidence, the quartz monzonite and monzogranite are I-type granites, and the syenogranite and granitic porphyry are classified are high fractionated I-type granites. Combined with the previous researches results in Jiaodong area, in the extensional tectonic setting generated by the subduction of the Paleo-pacific plate, magmas from the asthenosphere underplated into the lower crust, inducing partial melting of the lower crust material to form felsic magmas. After different degrees of fractional crystallization and evolution of felsic magmas, granites with varying degrees of differentiation in Laoshan area are formed ultimately.

Abstract:

Muscovite is a common mineral in peraluminous granites, it could be a mineral barometer to constrain the emplacement depth of peraluminous granites. Chemical compositions of muscovite from the Jintan two-mica granite are determined using electron microprobe. According to the calculation for the crystallization pressure of the muscovite, the pressure of emplacement of the Jintan pluton is 4.9×10⁸~6.1×10⁸ Pa with average 5.4×10⁸ Pa, corresponding to 16~20 km with average 18 km in depth. Combing with previous studies, we suggest that the emplace depth is 17~19 km, and we can presume that crustal thickness of South China in the Indosinian period was likely ≥50 km, but it may be denudated because of extensive weathering in the Yanshanian period, which can be a new explanation for the lacking Indosinian volcanic rocks in South China.

Abstract:

This article conducts carbon and oxygen isotopes, rare earth, and trace element geochemical analyses of carbonate samples from the Triassic Sanhedong Formation in the Hexi Area of the northwest Yunnan Province. The analyzed results demonstrate that their carbon and oxygen isotope values are consistent with the normal marine carbonate rocks. Samples from the Sanhedong Formation have a high Sr and Ba content, low Co, Cu, Th, U, Ho and total rare earth element content, and a negative anomaly of Eu, but they are slightly enriched in light rare earth elements. Paleosalinity parameter Z value, and Sr/Ba, Sr/Cu and Rb/Sr ratios indicate that they deposited in a marine saline water environment with dry-hot climate. The ratios of Cu/Zn, V/Cr, Ni/Co and U/Th indicate an anoxic environment. Y/Ho, δCe and δEu values indicate that the limestone of the Sanhedong Formation is less affected by diagenesis during sedimentation. These characters are similar to that of the Xujiahe Formation in the northern part of the Sichuan Basin, indicating that the Lanping Basin and the Sichuan Basin in the Upper Yangtze Plate probably have a similar tectonic and sedimentary environment during Late Triassic, which can help to study the paleoenvironment and tectonic attributes of the Lanping-Simao Block.

Abstract:

The environmental changes in the Ediacaran epigenetic system of the Earth are closely linked to the evolution of organisms. However, there is still ongoing debate surrounding their interaction. This study focuses on the carbonate sedimentary sequences of the Ediacaran Doushantuo Formation in the Jiulongwan section of the Three Gorges Region, South China. The rare earth elements information was extracted from the carbonate phase using dilute acetic acid distribution leaching. The obtained data was then utilized to construct the evolution curve of Ce anomalies, which underwent a process involving of reduction/manganization-strong oxidation-suboxidation-strong oxidation-weak oxidation/reduction. Two significant negative Ce anomalies were observed, indicating the occurrence of two significant oxygenation stages during the prolonged oxidation process of the Ediacaran Doushantuo shallow water. These two oxygenation events align with the periodic oxidation of deep water at 632 Ma and 580 Ma, respectively. Moreover, Ce negative anomalies were also found in contemporaneous sedimentary sequences in Australia, suggesting that global oxygenation events occurred in the Ediacaran Doushantuo ocean. The fossil record of the Doushantuo Formation in the Yangtze Plateform reveals that the duration of Doushantuo ocean oxidation corresponds to the production strata of major fossil groups. This finding supports the understanding that marine oxidation facilitated the origin and evolution of Ediacaran Doushantuo metazoans.

Abstract:

Recently, the bauxite gas reservoir of Taiyuan Formation has become a hot spot of exploration in Longdong area of Ordos Basin. In order to systematically explore the distribution of bauxite rock and the main controlling factors of reservoir formation, based on the latest drilling cores, rock slices, three-dimensional seismic, logging, scanning electron microscopy, model forward modeling and other methods, the distribution characteristics of bauxite rock in Taiyuan Formation were studied in detail, and then the main controlling factors of bauxite rock reservoir formation were expounded. The results show that the aluminiferous rock series has a typical five-stage type in the longitudinal direction, in which the C section is the main reservoir section of the bauxite rock, and the content of diaspore is more than 80%. The longitudinal lithologic association of the aluminiferous rock series is mainly controlled by the karst paleogeomorphology unit. The distribution characteristics of bauxite in karst highland, karst slope and karst depression are punctate, banded and flaky, respectively. The bauxite reservoir in the karst slope area is the most developed. The enrichment of natural gas in bauxite rock is mainly controlled by high-quality reservoirs, faults, fractures and structural positions. Reservoirs are the premise of natural gas enrichment and high yield. Early faults show construction effect, and late faults show destruction effect. Fractures can improve reservoir physical properties. Low-amplitude structures or nose-like traps in high structural parts are more likely to accumulate. Karst slope area is the most favorable paleogeomorphologic unit for natural gas accumulation in bauxite rock.

Abstract:

The potassium and lithium-rich brine is found in the central and northern part of Jiangling depression, while the southwest area is dominated by solid evaporites without potassium and lithium. This study aims to investigate the evolution of the paleo-saline lake brine in the southwestern Jiangling depression and sources of K and Li by the chemical composition of halite fluid inclusions of well ZK0303. Microscopic observations revealed the presence of primary fluid inclusions with chevron and cumulate structures in three groups of halite layers. The concentrations of Li, K, Mg, Ca, Br from the individual primary fluid inclusions were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). According to the analysis of experimental data, the brine of Eocene halite fluid inclusion in the southwestern of the Jiangling depression is Na-K-Mg-Ca-Cl type, in which the highest concentration of K is 3 362.15 mg/L, and the highest concentration of Li is 15.10 mg/L. The relationship between Mg-Ca-2K of three halite layers in well ZK0303 shows that the brine of Eocene saline lake in the southwestern depression reached the stage of sylvite precipitation. The changes of each ion concentration of the three halite layers show that the degree of evaporation of Eocene saline lake had changed from low to high and then decreased. According to previous studies, the sources of Li and K in the brine are closely related to the basalt in the depression. However, the southwest area of the depression is far from the basalt distribution area, and it is difficult to obtain sufficient material supply. Lithium and K of the Eocene saline lake brine in this area may come from the dissolution of early halite in addition to evaporation.

Abstract:

The Mengyejing potash deposit, which is located in the Simao Basin, Yunnan, contains different clastic rocks, namely greyish-green breccias coexisting with potash veins ("green potash"), brownish-red breccias coexisting with potash veins ("red potash") and yellowish-brown mudstones. XRD, SEM and TEM analyses were performed on those fine-grained clays extracted from clastic components. SEM and TEM observation suggests that those clay minerals are mainly composed of hexagonal, euhedral illites. It is very likely those illites are authigenic origin. The XRD results show that the "red potash" are composed of chlorite and illite, whereas both "green potash" and yellowish-brown mudstone contain "pararectorite" type clays, in addition to chlorite and illite. The Kübler values (indication of illite crystallinity) of the "red potash" range from 0.327 to 0.452°Δ2θ, which are much higher than those of the "green potash" and yellowish-brown mudstone (0.221 to 0.283°Δ2θ), indicating illites from the "green potash" and yellowish-brown mudstones have higher crystallinities than those from the "red potash". The "green potash" and "red potash" derived from the same provenance, and have undergone similar geologic processes. Thus the discrepancies with respect to clay assemblages and crystallinities among different clastic sediments were not merely caused by temperature and pressure. Previous studies have shown that the "green potash" were more reductive, imposed by more bacterial activities and had lower pH values, which are favourable to facilitate the crystallization of illite.

Abstract:

The crystal chemical mechanism of mineral cleavage/fracture and its relationship with interplanar spacing were quantitatively studied using density functional theory, broken bond theory, and crystal chemistry properties. It was found that the common cleavage/fracture planes of minerals do not always correspond to the crystal planes with the maximum interplanar spacing, showing a weak correlation. The theoretical calculations suggested that the common cleavage/fracture planes of minerals correspond to the crystal planes with the lowest surface energy, and the surface energy is positively correlated with the reticular density and the average broken bond number τ of the crystal plane atoms. The interplanar spacing is positively correlated with the reticular density, implying that when crystal planes with large interplanar spacing become common cleavage/fracture planes, the surface energy needs to be reduced by decreasing the average fracture bond number τ of the crystal plane atoms. However, the analysis revealed a poor correlation between the interplanar spacing and τ, which indicates that the interplanar spacing is not directly related to the cleavage/fracture patterns of minerals. The results of this study can provide theoretical insights for research on the cleavage/fracture patterns of minerals and surface properties.

Abstract:

In recent years, the Tanshan-Shangfu Nb-Ta-Li-Be metallogenic prospective area has been predicted in the southern of Jiuling area, northwest Jiangxi Province. Mineralization types include granite-type and aplite-type. Study on the formation age and genetic mechanism of rare metal deposits, is the key points of the enrichment and mineralization of rare metals in Jiuling area. Based on the study of the columbite-group minerals U-Pb geochronology, petrography and petrogeochemistry, to determine the diagenetic age and mineralization age, rock formation and magma source characters of the Nb-Ta-bearing aplite, and make analysis on its metallogenic potential. The LA-ICP-MS niobite-tantalite U-Pb dating yields an age of 142±1 Ma, suggesting that the Nb-Ta-bearing aplite was formed in the Early Yanshanian period. The aplite is characterized by rich silica, alkali and aluminum, poor titanium and ∑REE, the wide range of Rb/Sr, and there exists obvious enrichment of niobium-tantalum-lithium-rubidium, and CaO/(K₂O+Na₂O)≤0.10, Al₂O₃/TiO₂＞160, high differentiation index. The REE diagram shows rightward incline and obvious negative Eu abnormity. The spider diagram of trace elements shows left side is uplifted and right side is gentle. All of these indicate that the aplite show features of highly differentiated S-type granitoids. It may be that the metamorphic argillaceous rocks of the Neoproterozoic Shuangqiaoshan Group in the Jiuling area were partially melted to form granitic magma, which during the transition stage from syn-collision to post-collision, and then to form highly fractionated aplite. In the late stage of magmatic differentiation and evolution, the interaction between fluid and melt leads to the enrichment of metal ore-forming elements like Nb-Ta-Li in the highly fractionated aplite. The Dongcao Nb-Ta-bearing aplite and the Nanling Nb-Ta-bearing granite, the Dahutang Nb-Ta-bearing granite porphyry have similar geochemical characteristics. Which is regarded as the main metallogenic geological body in the Tanshan-Shangfu Nb-Ta-Li-Be metallogenic prospective area.

Abstract:

The north Wuyi area in Jiangxi Province is located on the southern side of the Pingxiang-Guangfeng junction zone on the Qinhang mineralization belt. Multiple tectonic events and magmatic activities formed a complex geological structure pattern in this area, and metallogenic potential of copper and lead-zinc polymetallic deposits is enormous. However, due to the generally small scale and insufficient research of lead-zinc deposits in the northern Wuyi area of Jiangxi Province, there is a lack of in-depth understanding of material sources, metallogenic conditions, and deposit genesis. This paper takes Laohudong Pb-Zn deposit in the northern Wuyi area of Jiangxi Prov-ince as the research object. EPMA, LA-ICP-MS and LA-MC-ICP-MS were used to reveal the major and trace element and sulfur isotope composition of sulfides, then many important information concerning the mineralization temperature, the source of metallogenic materials and the genesis of the deposit were investigated. EPMA testing shows that the Fe content in sphalerite ranges from 7.58% to 8.27%. Combined with LA-ICP-MS trace element testing, sphalerite is rich in Fe, Mn, Cu, Cd elements, followed by Co, Ni, Ag, In and Pb elements, the contents of Ga, Ge, As, Se, Sn and Bi elements are low. In sphalerite, Mn, Fe, Cd, In and Co exist in the form of isomorphism,while Cu, Ag, Pb exist in the form of isomorphism and microscopic inclusions. The content of Fe, the values of Ga/In (0.001~0.129), Zn/Cd (262~312) and calculation results of relevant formulas of sphalerite all indicated that sphalerite was formed under medium to high temperature mineralization conditions (about 327~337℃). The δ³⁴S of sphalerite and pyrite respectively concentrated between 2.07‰~4.16‰ and 0.82‰~3.19‰,they all indicated magmatic sulfur. Compared with multiple Pb-Zn deposits in China, the trace element composition of sphalerite in Laohudong Pb-Zn deposit is consistent with typical skarn deposits. The Laohudong Pb-Zn deposit has a close genetic relationship with the Gexianshan granite complex, and the age of Gexianshan granite complex (153.9±2.7 Ma and 162.8 ± 1.2 Ma) can represent the lower limit of the mineralization time, which is consistent with the range of the main polymetallic Pb-Zn deposits in the north Wuyi area.

Abstract:

In the process of ore prospecting prediction, basic geological big data has a significant impact, resulting in poor accuracy of screening results when applied to complex geological areas. Therefore, a remote sensing prospecting prediction method for Pengshan ore field in De'an County, Jiangxi Province was studied. As a typical ore field in the Pengshan area, the Xiabianshan tin ore area is analyzed for its geological characteristics and mineralization rules. Based on the analysis results and remote sensing technology, remote sensing prospecting elements and remote sensing alteration information are obtained. A remote sensing comprehensive information prospecting target area prediction model is established, and the quantitative prediction results of the prospecting target area in the Pengshan area are obtained. The prediction results show that three typical prospecting target areas have been quantitatively predicted in the study area, located on the northwest, west, and east sides of the area, mainly consisting of annular and banded structures, and the structural development directions are mainly northeast, northwest, and nearly south-north. The remote sensing alteration information extracted mainly includes carbonation, epidotization, chloritization, sericitization, kaolinization, and iron staining. All three target areas have good mineralization conditions. The field investigations have confirmed the existence of kaolinization, iron staining and carbonation in the three target areas, and the contents of Cu and Au in the altered rock blocks are high. The predicted results have been confirmed, providing reliable reference for ore prospecting in this area.

Abstract:

Ferrihydrite is a common iron oxide mineral in soil and also the main arsenic carrying mineral. Releasing arsenic from ferrihydrite is a way to alleviate arsenic pollution in soil. In this paper, it is intended to promote the release of arsenic by biological reduction of arsenic-containing ferrihydrite (As-Fh) by sulfate reducing bacteria (SRB) and acidiphilium cryptum JF-5 (JF-5), so as to achieve the purpose of soil remediation.To this end, two kinds of microbial shaker experiment and biological injection experiment were carried out by collecting typical arsenic-containing ferrihydrite from Shimen mining area in Hunan Province, to explore the arsenic release and form of ferrihydrite, the change of suspended particulate matter in the process of biological dissolution, and the permeability of the system. The results showed that: ① In two cycles, according to the total amount of arsenic released, JF-5+SRB operations> JF-5+JF-5 operations>SRB+JF-5 operations>SRB+SRB operations, corresponding to these operations were able to release 16.4,16.2,7.3 and 3.3 mg per gram of ferrihydrite, respectively; ② Hydrochemical analysis also showed that SRB could provide stronger reducibility than JF-5 under the same operation; ③ The biological column experiment showed that compared with SRB, JF-5 injection could produce iron suspended particulate matter with an average concentration of 1 419 mg/L, 7.25 times that of SRB; At the same time, the permeability of SRB column system (mean water pressure difference of 0.51 psi) was significantly better than that of JF-5 (mean water pressure difference of 2.22 psi), and the dispersion of highly suspended particles was the main reason for the permeability change.These results demonstrate that continuous injection of SRB into the ferrihydrite system is an effective technique for reducing arsenic concentration in soil.

Abstract:

Muscovite is the important component of mineral aerosols in the atmosphere. The researches for heterogeneous reactions of common gases in the atmosphere on the surface of muscovite will reveal the chemical reaction process in the atmosphere to a certain extent. In this study, the heterogeneous reaction of SO₂ and NO₂ on the surface of muscovite particles was investigated by a self-made quartz glass microreactor, and the effects of relative humidity (RH) and light on the reaction were also discussed. The results showed that muscovite has certain adsorption activity for both SO₂ and NO₂. The products in SO₂ reaction with and without ultraviolet irradiation were mainly salt compounds containing SO^2-₄ and SO^2-₃, respectively, while the products in NO₂ reaction were always mainly salt compounds containing NO^-₃. The increase of RH or ultraviolet light had a promoting effect on the reaction, and they had a synergistic effect on the formation of sulfate and nitrate. When SO₂ and NO₂ coexist on the surface of muscovite, there were both synergistic effect and competitive effect, and the generation amount of SO^2-₄ and NO^-₃ was 2.09 times and 77% of that in the presence of a single gas, respectively. Therefore, NO₂ promoted the formation of sulfate, but SO₂ had a significant inhibitory effect on the formation of nitrate.

Abstract:

0.015%, 0.025%, 0.05% and 0.1% δ-MnO₂ were added to yellow soil of Guizhou Qinglong antimony mine by in-situ processing. After 20 days of flooding, the content of Mn and Sb in suspension and the content of each speciation of Mn and Sb in soil were determined, and the correlation analysis of each parameter were performed to clarify the effect of Mn oxides on the speciations of Sb. The results showed that the contents of Mn in suspension and three speciations of Mn in soil gradually increased with the increase of δ-MnO₂, and the order of Mn content of all speciations in soil was consistent with that in control soil. With the increase of δ-MnO₂, the contents of non-specific adsorption, specific adsorption and residual Sb decreased, while the content of Fe/Mn/Al oxide bound Sb increased. The Mn loading was significant positive correlation with all speciations of Mn and Fe/Mn/Al oxide bound Sb (P<0.05), and significant negative correlation (P<0.1) with residual Sb. Fe/Mn/Al oxide bound Sb and residual Sb were significant positive correlation (P<0.05) and negative correlation (P<0.1) with all speciations of Mn, respectively. δ-MnO₂ existed in various speciations in yellow soil. After flooding, the speciations of Mn transformed to different degrees, and various speciations of Mn were oxidized, adsorbed and complexed with Sb, which made the non-specific adsorption Sb, specific adsorption Sb and residual Sb transform to Fe/Mn/Al oxide bound Sb in soil.

Abstract:

Mississippi Valley-type (MVT) lead-zinc deposits are closely related to evaporite rocks, however, the fact that evaporite minerals dissolve or transform into other minerals and "disappear" is often overlooked. Drawing on previous research results, we summarized the transformation and identification characteristics of evaporite, and its relationship with MVT Zn-Pb mineralization that is reflected in the source of mineralizing fluids, the source of sulfur, and the ore-bearing structures. The formation of MVT deposits involves basin brines, primarily derived from evaporated seawater, with a small portion originating from the dissolution of evaporite rocks. Meanwhile, the deve-lopment of regional evaporite rocks indicates the formation conditions for mineralizing fluids. The sulfur in lead-zinc metal sulfides totally comes from the reduction of sulfates, and evaporite minerals, such as gypsum, anhydrite, etc., are important suppliers of sulfates. Moreover, dissolution-collapse evaporites form breccias and collapse spaces, and lead-zinc mineralization can occur within the breccias and/or adjacent strata. Salt diapiric structures create favorable structural/chemical traps for fluid accumulation and mineral precipitation, and lead-zinc mineralization can be found in the caprock, transition zones and peridiapiric rocks of salt diapirs, vertically oriented salt diapiric breccia pipes, or top of domes formed by lateral salt diapirism. Pseudomorphs after evaporite minerals and residual evaporite minerals are direct evidence of the existence of "disappeared" evaporites, while minerals such as albite and scapolite, length-slow chalcedony/quartz, alkali-enriched double-terminated quartz, etc., may indicate the past existence of evaporites. The evaporite dissolution-collapse structures exhibit the characteristics of lateral extension along with the stratigraphic strike, and salt diapiric structures have features such as cross-cutting and breccias derived from lower strata, both of which can help identify evaporite-related structures. In exploration for MVT deposits, the regional stratigraphic record of evaporative sedimentary environments is necessary for MVT mineralization, and evaporite dissolution-collapse structures as well as salt diapiric structures are important prospecting targets.

Abstract:

The mafic-ultramafic intrusions contain a large amount of information from the deep earth, and the magmatic deposits they contain are of great economic value. Fe is an element directly involved in mineralization, and Fe isotope method has a natural advantage in tracing the source of metallogenic material and metallogenic process. In recent years, with the appearance and development of MC-ICP-MS, many scholars have carried out a series of Fe isotope studies on mafic-ultramafic intrusions and made important progress. In this paper, the fractionation mechanism of Fe isotopes in mafic-ultramafic intrusions is discussed by summarizing the composition characteristics of Fe isotopes in magmatism and metallogenesis. The results show that the composition of Fe isotope in different geological bodies is different. The chondrite represents the initial Fe isotope composition of the earth, and the other geological bodies are subjected to different degrees of later geological processes and produce fractionation of Fe isotope. The framework of Fe isotope fractionation mechanism in mafic-ultramafic intrusions is constructed: Fe isotope fractionation mechanism includes thermodynamic equilibrium fractionation and kinetic fractionation. In natural minerals, Fe³⁺ forms stronger chemical bonds than Fe²⁺, so mineral rich in Fe³⁺ (such as magnetite) are more enriched in heavy isotopes than mineral rich in Fe²⁺ (such as pyrrhotite and pentlandite). Many kinetic processes such as redox process, fractional crystallization, partial melting and diffusion are the factors leading to kinetic fractionation. Due to its unique geochemical properties, Fe isotopes have a wide application and prospect in the fields of Cu-Ni-PGE sulfide deposits, V-Ti magnetite deposits and chromite deposits related to mafic-ultramafic intrusions. Combined with other stable isotopes, such as Li-S-Mg-Ni isotopes, they can be used to trace the assimilation of sediment, invert the crystallization process of sulfide melt and reveal the genesis of deposit.

Abstract:

Zircon is a robust dating accessory mineral, and often develop thin ring (generally less than 5 μm), which poses challenges to obtaining accurate ages of this ring. This article conducted a series of comparative and experimental studies from three aspects: ① sample preparation methods; ② experimental conditions, and ③ data algorithms to evaluate the reliability of multi-pulse short time ablation method for LA-ICP-MS U-Pb dating of ultra-thin ring (~1 μm) in natural zircons. The results showed that although the double-sided adhesive sample preparation method is fast, the sample observation under microscopic and laser system are poor. The resin-fixed preparation method has high efficiency, is easy to observe with transmitted light and reflected light, and is conducive to sample surface focusing. For laser setting parameters, data results in 5 Hz/2 s ablation are more stable than those in 10 Hz/1s ablation. The peak integration method is superior to linear regression and mean value methods for data reduction. Our results show that by using rapid erosion method for Pleovice and Qinghu zircon dating are consistent with the recommended values within the error range, but the data error is relatively large (~5%, 1σ). The zircon standards Pleovice and Qinghu are improved by 3% and 2% respectively when the 50%~60% of each signal peak value peak integration method was used. The combination of resin-fixed sample preparation, peak integration data processing method and multi-pulse short time ablation method can get an acceptable age of ultra-thin zircon ring. This method can provide more age constraints for multi-age geological processes.

Abstract:

The determination of Ca isotope ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) is sensitive to the matrix effect, especially that is generated by Cr elements, which leads to a deviation in Ca isotope compositions. Traditional methods using dilute HCl medium and strong acid cation exchange resin can achieve high-efficiency separation of most matrix elements and Ca, except Cr, where nearly 10% of Cr cannot be removed from Ca elution. For geological samples with high Cr, such as ultramafic rocks, the Cr/Ca ratio can be as high as 10. To achieve Ca isotope analysis of these special geological samples, here we studied the elution of Cr-Ca in concentrated HCl medium based on AG50W-X12 (200-400 mesh) strong acid cation exchange resin. The results showed that efficient and rapid separation of Cr-Ca can be achieved when using 10 mol/L HCl, with a Cr separation rate >99.9%. Moreover, this method can achieve efficient and rapid separation of elements such as K, Mg and Al from Ca. To test the validation of this method for Ca isotope analysis, δ⁴⁴/⁴²Ca of the Ca single-element solution after column separation was determined using MC-ICPMS, with the results consistent with the theoretical value within the analytical error. This indicates that this method is efficient for Ca element purification and valid for Ca isotope analysis for those high Cr samples.

Abstract:

This paper discusses the petrogenesis of the two-mica granite and its genetic relationship with pegmatite in Jiajika area, west Sichuan Province, by detailed field investigation and laboratory analysis. The whole rock analytical results show that SiO₂ content of two-mica granite is 73.93%~75.06%, and total alkali is 7.90%~8.36% with high concentration of K, suggesting high-K calc-alkaline series; the content of Al₂O₃ is 14.24%~14.77%, and A/CNK=1.14~1.24, implying strong peraluminous S type granite; ΣREE=31.18×10^-6~41.67×10^-6,LREE/HREE=4.15~6.41,δEu=0.46~0.70, and CaO/Na₂O=0.07~0.12(<0.3),indicating that its source might have been pelite with rare content of psammite, and high ratio of Al₂O₃/TiO₂ (133.1~279.8) implies that it is high-pressure-low-temperature post-collision granite. The SiO₂ content of the granite pegmatite is 72.59%~80.91%, the total alkali is 5.26%~10.60%, Al₂O₃ is 11.79%~17.64%, σ=0.74~3.80; A/CNK=0.98~2.38; ΣREE=4.03×10^-6~8.29×10^-6, LREE/HREE=2.61~10.40, and δEu=0.18~0.68. There are considerable differences between two-mica granite and granite pegmatite in the aspect of the content of major and trace elements. And there is close genetic relationship between granite and pegmatite in the area. Magma immiscibility might be the key factor for the formation of (ore-bearing) granite pegmatite. The pegmatite melt riched in volatile components might be separated during the upwelling of granite magma and metasomatized minerals in wall rock to further concentrate rare metal elements during its migration. The difference between two-mica granite and pegmatite might cause the apparent differences in REEs and elements such as Th, Sr, Ti, Y, Rb and Nb. The different characteristics of pathways and environments that the pegmatite melt passed and emplaced might have resulted in element concentration variance in different sites. In comparison with two-mica granite, there existed a certain degree of jumping characteristic during the formation and evolution of the pegmatite in Jiajika area.

Abstract:

Guilin Chicken Blood Red Jasper (CBRJ) is a kind of quartz jasper. It is characterized by bright red to black colors and high hardness. However, few researches have been focused on the field occurrence, geological background, rock structure and genesis of its color. Field surveys indicate that the Guilin CBRJ is hosted in low-grade metamorphic sandstones which experienced vapor-water hydrothermal metamorphism and iron oxide dissemination. It occurs in the Sanmenjie Formation of Neoproterozoic Danzhou Group in Longsheng area in the north of Guangxi. Tectonically, the ore deposit of Guilin CBRJ is located at the juncture of Yangtze and Cathaysian plates, which has undergone a complex geological process. Its formation was related to multi-phase tectono-magmatic activities from Neoproterozoic to Triassic. Detailed analyses of mineralogy, micro-texture and geochemical composition of Guilin CBRJ were carried out by polarizing microscope, X-ray diffraction, and electronic microprobe. The results indicate that the CBRJ is mainly composed of quartz and hematite, with dolomites in some samples. Quartz grains exhibit two types of allotriomorphic equigranular texture and idiomorphic porphyroblastic texture. The latter one, in which distinct enlargement texture can be observed, reveals a metasomatic metamorphism phase. Hematite occurs in three types: ① single crystal existent between or inside the quartz particles, ② dusty crystals wrapped in the quartz particles, and ③ disseminated crystals filled between the quartz particles. The Fe³⁺ in the hematite should be responsible for the color of the CBRJ. Electron microprobe analysis shows that the hematites of single crystal and disseminated crystals have 78.9%～85.6% iron oxides, but the dusty crystal is too small to be analyzed. In combination with the different generations of quartz and hematite, the authors have reached the conclusion that the formation of different types of these minerals in the Guilin CBRJ was consistent with the regionally geological evolution in this area.

Abstract:

The Hongyuntan iron deposit is hosted in pyroclastic rocks of the Lower Carboniferous Yamansu Formation. The ore bodies occur as layers, stratoid bodies or lenses. The principal ore mineral is magnetite, together with minor maghemite, specularite, pyrite and trace chalcopyrite. The gangue minerals include garnet, diopside, actinolite, chlorite, tremolite, epidote, biotite, albite and quartz. The ore structures are mainly of massive and disseminated forms, with occasional banded or veined forms. The ore textures are of subhedral-anhedral granular and metasomatic types. The wall rock alteration shows symmetrical zoning, and the alteration colors change from dark to light from ore bodies outwards. On the basis of observed mineral assemblages and ore fabrics, two periods of ore deposition were recognized, i.e., skarn period and hydrothermal ore-forming period, which could be further subdivided into four metallogenic stages, namely skarn stage, retrograde alteration stage (main ore-forming stage), early hydrothermal stage and quartz-sulfide stage. Electron microprobe analyses show that the end member of garnet is mainly andradite-grossularite. The composition of pyroxene is mainly diopside-asteroite. The amphiboles is composed mainly of actinolite and tremolite with minor magnesiohornblende. The composition of these skarn minerals suggests that skarn in the Hongyuntan iron deposit is calcic skarn, belonging to metasomatic skarn. The characteristics of main and trace elements suggest that the formation of magnetite was closely related to the skarn. In combination with geological characteristics, the authors suggest that the skarn might have resulted from interaction between Ca-rich pyroclastic and Fe-rich magmatic hydrothermal fluid which was transported along the fault system. The formation of magnetite was hence related to the regressive metamorphism of the skarn.

Abstract:

This paper has mainly recommended a mineral abbreviation list (see Table 2 and Table 3). Table 2, which contains 243 minerals, was compiled by IUGS Subcommittee on the Systematic of Metamorphic Rocks (SCMR) in 2007. The author selected other 29 minerals and, on such a basis, formulated Table 3. Thus, the total mineral abbreviations come to 272. It is hoped that they can be popularized in future and become more and more perfect through utilization, so as to provide a basis for ultimate standardization and unification.

Abstract:

This paper presents partition coefficients of 69 chemical elements (Li, Rb,Cs, K, Na, Ca, Ba, Sr, Mn, Fe, Mg, Cu, Pb, Zn, Co, Ni, Be, La, Ce, Nd,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Cr, In, Ga, Al, B,Cd, Sb, Bi, U, Th, Zr, Hf, Si, Ti, Ge, Sn, Mo, Nb, Ta, W, V, P, F, Cl,S, N, O, C, As, Pu, Re, Os, He, Ne, Ar, Kr and Xe) and the univalent radical (OH) in 28 minerals (olivine, clinopyroxene, orthopyroxene, amphibole,biotite, Phlogopite, plagiocla-se, K--feldspar, quartz, magnetite, ilmenite, garnet,zircon, apatite, allanite, topaz, sphene, cordierite, hauyne, leucite, nepheline,whit-lockite, brookite, petovskite, melilite, armalcolite, spinel and rutile) from 8 types of rocks, namely metaluminous (ultra) basic rock, peralkaline (ultra) basic rock, metaluminous intermediate rock, peralkaline intermediate rock,metaluminous acid rock, peralkaline acid rock, peraluminous acid rock and ultra-acid rock. It is found through an integrated ahalysis and comparison that the composition and structure of minnerals and melts seem to be the most important factors controlling mineral-melt element partitioning. Importanceshould be attached to minral structure and Al-supersaturation of melt which have, not been discussed by research workers. Finally, the present state and theproblems to be solved in the study of mineral--melt element partition coefficients are analysed, and the future trends of this research field are predibted.

Abstract:

本文以表格的形式列举了经国际矿物学协会(IMA)新矿物与矿物命名委员会(CNMMN)批准、并于2003年度正式发表的新矿物共55种,其中硅酸盐31种,磷酸盐5种,砷酸盐2种,硫酸盐4种,硫化物3种,碳酸盐2种,钒酸盐2种,硼酸盐1种,硒化物1种,硫盐1种,氧化物1种,氢氧化物1种,复杂卤化物1种.文中表格依次列出了矿物的中外文名称及化学式、晶系及晶胞参数、主要粉晶数据、物理性质、光学性质、产状及共生(伴生)组合等.

Abstract:

The combination of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and laser ablation provides a useful tool for tracing the geological process by analyzing minerals under microscales. As one of the non-traditional stable isotopes, boron isotope has attracted more and more attention. In this study, the authors developed an in-situ method for high-precision analysis of B isotope in tourmaline with high-content boron and muscovite with low-content boron. Tourmaline and glass reference materials were applied to correcting the mass fractionation respectively, and in-situ B isotopes of two natural samples from southwestern Tianshan were also tested. In addition, the boron isotope of the in-house standard T-PKU was calibrated as -13.07‰±0.42‰ (2SD, n=66). The above testing results reveal that the condition of LA-MC-ICPMS is stable for a long term and suitable to producing high quality data about tourmaline with minimum spot size of 10 μm and muscovite with > 20×10^-6 B concentration. The B isotopes of tourmaline and paragonite in Tianshan samples are helpful for tracing fluids sources.

Abstract:

High grade black jadeite is a kind of upscale and fashionable jade material that has become one of the jadeites characterized by fastest growing values in the past 20 years. Based on a comparison of mineralogical and geochemical characteristics between black jadeites (inky black jades）from different producing areas of the world, the authors hold that the black jadeites currently on the market can be mainly classified into jadeite jade, omphacitic jadeite jade and hornblende jade whose main components are jadeite, omphacite and dark green hornblende respectively. They include black chicken jade, ink jadeite and black kosmochlor from Myanmar and jade negro and galactic gold from Guatemala, with black chicken jades similar to those from Myanmar also seen in Japan and Kazakhstan. The research results suggest that the main mineral composition, jade structure and inclusion characteristic combinations of black jadeite jades from different producing areas have their respective typomorphic natures, which can be used as the distinctive characteristics for their sources.

Abstract:

Early Paleozoic volcanic rocks in Tianshui and Baoji areas along the eastern segment of North Qilian orogenic belt consists of Hongtubu basaltic lavas and Chenjiahe intermediate-acid volcanic rocks. Geochemical analyses show that Hongtubu basaltic lavas are similar to the intercalated basalts in Chenjiahe intermediate-acid volcanic rocks in characteristics, both fallen in the tholeiite series with high TiO2 (1.50%～2.73%). Their∑REE are 65.97×10-6～133.46×10-6 and 78.04×10-6～175.55×10-6 respectively， both are slightly enriched in LREE ［(La/YbN being 2.00～4.40 and 2.71～4.40 respectively］，and both have no obvious Eu anomaly or weak Eu negative anomaly（δEu being 0.85～1.10 and 0.85～0.99 respectively）. Basalts from two groups are typically characterized by selected enrichment of LILEs, low abundances of HFSEs relative to NMORB, and prominent troughs of Nb and Ta, with low Nb/La ratio（0.28～0.43）, which indicates the affinity of these volcanic rocks to island arc tholeiite（IAT）. In addition, εNd（t）（+2.22～+4.08）values of basalts suggest that their mantle sources are similar to the depleted mantle source. Zr/Nb=17.21～36.33 and Ce/Nb=5.73～8.17, implying geochemical characteristics of N-MORB. Sr, Nd and Pb isotopes from Hongtubu basalts are similar to those in Chenjiahe basalts in composition. In the diagrams of εNd(t)-(87Sr/86Sr)t, (207Pb/204Pb)t-(206Pb/204Pb)t,(87Sr/86Sr)t-(206Pb/204Pb)t and εNd(t)-(206Pb/204Pb)t for basalts, the data are fallen in the DM, EMⅠand EMⅡ areas, probably with a little crustalontamination, indicating that the magma of basalts might have had a mixed gin.Thentermediate-acid volcanic rocks from Chenjiahe belong to the calc-alkaline series,they have relatively high abundances of REE∑REE=127.51×10-6～276.01×10-6）, and are significantly enriched in LREE[（La/YbN= 4.79～13.51]. Most intermediate-acid volcanic rocks show weak Eu negative anomaly (δEu=0.53～1.20). The trace element patterns of Chenjiahe acid volcanic rocks are similar to those of the ocean ridge granite (ORG), with marked troughs of Nb, Ta, Zr and Hf. A synthetic study shows that the Chenjiahe intermediate-acid volcanic rocks in the eastern segment of North Qilian orogenic belt were formed in an island-arc setting, whereas the Hongtubu basalts were formed in an intra-arc rift setting (or an initial back-arc basin setting), probably being products of the early spreading evolution of the island_arc system towards the back-arc basin in the eastern segment of North Qilian during late Early Paleozoic. The results obtained provide evidence for the existence of the trench-arc-basin system at the juncture of Qilian and North Qinling orogenic belts.

Abstract:

The geochemical characteristics and abnormal sources of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil of Southern Xuancheng were analyzed and studied by using the 1:250 000 land quality geochemical survey data. It is found that the geological background is the main controlling factor for the content of soil elements, and that the spatial distribution characteristics of heavy metal elements in the surface and deep soil in the area are significantly consistent with the geological background and sedimentary environment. The high content of heavy metal in the soil parent rock geological background (Hetang Formation, Piyuancun Formation and Lantian Formation, etc) is the main influencing factor for the high anomaly of soil heavy metal elements. In addition, mining and atmospheric dry and wet deposition are also one of the factors affecting high anomaly of heavy metals in soil. It is found that Pb, Hg, Cd and Cr in soil have input sources of atmospheric dry and wet deposition. The main impact index of heavy metal in soil pollution risk in the survey areas was Cd. The proportion of samples that soil Cd exceeded the control value of soil pollution risk of agricultural land was 2.56%. The morphological analysis results show that soil Cd is mainly in ion-exchange state. Combined with crops investigation, it is found that there is a certain ecological risk in the area with high abnormal soil Cd.

Abstract:

The Cuonadong leucogranite is one of the most important parts of North Himalayan leucogranite belt. Geochemical data show that Cuonadong leucogranite is the calcium alkaline and strong peraluminous granite with high silica (SiO₂ is 74.20%~74.52%), poor iron (Fe₂O₃ is 0.04%~0.20%, FeO 0.04%~0.58%), poor magnesium (MgO is 0.06%~0.14%), and calcium alkaline (σ is 2.15~2.32) as well as strong peraluminous nature (A/CNK is 1.11~1.15). Its total rare earth is relatively low (∑REE is 47.24×10^-6~57.59×10^-6), with enrichment of LREE (LREE is 39.85×10^-6~49.23×10^-6), depletion of HREE (HREE is 6.91×10^-6~8.68×10^-6) and obvious negative Eu anomaly (0.49~0.80). It is characterized by an enrichment of some large ion lithophile elements (Rb, Th, U, K) and loss of high field strength elements (Nb, Ta, Zr Ti). Zircon U-Pb dating results show that the Cuonadong leucogranite's formation time is Miocene (21 Ma), which belongs to the peak of the late stage of north Himalayan leucogranite (24~12 Ma). Zircon εHf(t) values are negative with a wide variation (-3.92~-17.64), which shows that its magma source was the crust, mostly from the metapelite, with the probable mixing of many kinds of materials in its source. The petrogenesis of Cuonadong leucogranite is that the high Himalayan crystalline rock series experienced decompression melting during the rapid pull-back of the plate in the post-collision tectonic setting, with the initial magma crystallization temperature being 675~702℃.

Abstract:

Quantitatively determining the timescale during mantle-derived magma ascent from the source to eruption or emplacement is essential for the understanding of magmatism, however, the timescales of eruption/emplacement are still poorly constrained. Shanxi Datong Cenozoic volcanic field, north of the North China Craton, is an ideal area for the investigation. In this study, we focused on the mantle olivine xenocrysts entrained in ca. 0.2 Ma Shenquansi alkali basalt, and its timescale of residence in the host magma prior to eruption. According to mineral chemistry, cores of these mantle olivine xenocrysts have Fo values up to 97.7, which can be defined as extremely magnesian olivine. They are also characterized by the extremely low contents in Ca, Mn and Ni, suggesting they were captured from metasomatized mantle peridotite. Moreover, both of the mantle olivine xenocrysts display complex CaO profiles, attributed to complex magmatic processes in the magma plumbing system. The reaction rim widths of one olivine xenocryst vary significantly, implying it has experienced multiple crack processes when captured or dur- ing transport. The Fo values of the mantle olivine xenocrysts rims are about 70, indicating they are in diffusion equilibrium with the host magma (alkali basalt) at rims. Timescales obtained by Fe-Mg diffusion chronometry of olivine mantle xenocrysts show that they have only resided in the magma for months. For a lithospheric mantle thickness of 40~70 km, the fastest average ascent rate may exceed 500 m/d.

Abstract:

In this paper,LA-ICP-MS zircon U-Pb dating was carried out for four samples of volcanic rocks from Qingshan Group in Jiaodong area and, as a result, their concordant ages were obtained, which are 119.4±0.9 Ma, 118.2±1.0 Ma,120.2±0.9 Ma and 120.0±0.8 Ma, respectively. The results show that all the volcanic rocks in Jiaodong area were formed from about 120 Ma to 118 Ma in the Early Cretaceous period. The ages of Qingshan Group volcanic rocks from Shandong Province controlled by Tan-Lu fault are similar to those from the Su-Wan segment of the Tan-Lu fault zone,but younger than those around the Tan-Lu fault zone,which indicates that the duration of volcanic eruption along Tan-Lu fault is probably longer than the duration in other areas under the background of lithospheric thinning in eastern China. Geochemically, all the intermediate and acidic volcanic rocks have high K₂O, ALK, LREE values and low MgO, TiO₂, Ni, Cr, HREE values. According to the geochemical features, the volcanic rocks can be subdivided into trachyte-trachydacite and rhyolite. The trachyte-trachydacite is characterized by LILE enrichment(Rb,Ba,K)and HFSE depletion(Nb,Ta,Ti,P), but the rhyolite exhibits stronger depletion of Ba,Sr and HFSE (Ti,P). Compared with the rhyolite,the trachyte-trachydacite possesses higher Sr and Ba values as well as La/Nb and Ba/Nb ratios,but lower Rb/Ba ratios and δEu values. All these data indicate that they might have been derived from different magma sources. It is inferred that the trachyte-trachydacite rocks were derived from the mixture of the partial melting of the lower crust(Yangtze Craton or North China Craton)and enriched lithospheric mantle. In addition, the rhyolites were related to the partial melting of the lower crust in the regional extension environment and high geothermal anomaly background with crystallization differentiation during the magma evolution.

Abstract:

Cordierite is a mineral material characterized by low thermal expansion coefficient and good thermal shock resistance. Cordierite mineral material is relatively rare in nature, so cordierite is synthesized usually by the method of artificial synthesis. Based on the newest investigation results of synthetic cordierite, this paper deals with the progress of researches on such synthesis methods of cordierite as high purity oxide solid reaction at high temperature, natural mineral solid reaction at high temperature, the utilization of industrial wasted materials, the employment of agricultural wasted materials, the sol-gel and the low-temperature combustion synthesis. At present, the method of natural mineral solid reaction at high temperature is used for the preparation of cordierite in industry. In spite of a lot of advantages, this method also has many disadvantages. Therefore, the development trend of cordierite synthesis seems to solve the problem as to how to apply other synthesis methods to industrial preparation.

Abstract:

At present, the infrared transmission spectroscopy is the best technique for determining whether jadeite is polymer-impregnated or not, and the infrared reflectance spectroscopy is a nondestructive and rapid determination method that provides mainly the fundamental frequency vibration spectra data of minerals and shows new application potentials in gemological research, especially in the identification of gem species. The gemological application of IR reflectance spectroscopy and the identification system of IR spectra of gems, including a database of 318 spectra and a searching and identifying program, are described in this paper.

Abstract:

Petrology, geochemical and Nd isotopic data are reported for the Neoproterozoic Danba metabasalt in the Kangdian Rift on the western margin of the Yangtze block. Samples were collected from alkaline basalts, which are enriched in MgO, TiO₂, with Mg^# being 0.51～0.59. They have high total rare earth elements and show high fractionation between LREE and HREE. The trace elements are characterized obviously by enrichment of Th, Nb, Ta, Zr, Hf and LREE but depletion of Y and HREE. Their geochemical and Nd isotopic characteristics suggest that they are similar to OIB. The basaltic magma was generated in an intraplate setting, and was generated by partial melting of OIB mantle source region, with variable degrees of contamination of SCLM during magma ascending; in addition, some samples might have experienced contamination of the lower crust. These samples reveal some plume magmatism characteristics in petrochemistry, and imply that magmatism was probably related to the Neoproterozoic plume event, which resulted in the breakup of Rodinia supercontinent.

Abstract:

As more and more treated turquoises appear on Chinese gem market, the authors collected lots of turquoises from different deposits on Chinese gem market in order to sum up the characteristics of the natural turquoises on Chinese gem market. At the same time, different types of treated turquoises were studied to find general difference between them and natural turquoises. The results show that natural turquoise and treated turquoise have different shades of color, inclusions and appearances. IR spectra of both natural and treated turquoises were studied, indicating that there are absorption peaks at 1 735, 1 600 and 1?500 cm^-1 in treated turquoises, which are caused by the man-made polymer. If the turquoise is treated by polymer, there are absorption peaks at 1 735, 1 600 and1 500 cm^-1 in a turquoise, and this can serve as convincing evidence in this aspect.

Abstract:

The newly-exposed lower strata of the Xiamaling Formation near Tielingzi Village in Jixian County contain rich siderites. This paper reports the basic geological characteristics of these siderite-rich strata in terms of the field outcrop, petrology and major elements. Studies show that the profile is characterized by black shale interbedded with silty iron-rich layers/siderite concrete layers, and also has minor siltstone. Some iron-rich strata have turned into limonite layers in the outcrop because of intense weathering. Siderite is the main iron mineral phase in the strata. Siderites can form iron concretes, showing micritic or microcrystalline granulitic textures under the microscope, or form silty ferruginous layers with almost a comparable amount of silty quartz; it can also distributed sporadically in siltstone and black shale with relatively coarse particles. There also exists very little siderite residue in weathered limonite layers. The overall features of major elements show that the strata are rich in SiO₂, TFe and TOC, but poor in MnO, CaO, MgO, P₂O₅ and S. Except for ferriciron in weathered layers, there is mainly ferrous iron in the strata. The TOC content decreases in order of siderite concrete, silty iron-rich layer, black shale and siltstone. The correlation diagram between TFe and Al₂O₃ content shows a negative correlation in iron-rich layers, while a positive correlation between them exists in normal black shale and siltstone, which suggests that iron in the former form originated from the ocean itself, while iron in the latter form originated mainly from terrigenous detritus. In addition, FeO content has a positive correlation with TOC content in fresh samples, which implies that the genesis of siderites may have some relationship with organic matter.

Abstract:

From the discovery of the first new mineral hsianghualite in 1958 to the end of 1995,74 new minerals found in China had been approved by IMA CNMMN. Among them, 2/3 were discovered after 1981. The discovery of new minerals in China has the following features:(1) With the development of analytical methods, the number of new minerals discovered per year increases gradually: from the end of 1950s to 1960s, only one new mineral was discovered every year on the average, whereas from 1980s till now, three new minerals were discovered averagely every year. (2) The structures of many new minerals have been determined. (3) Most of the new minerals are in the lower category, mainly in the monoclinic system, and perfect crystals are rare; hsianghualite has the most abundant crystal faces, whose ideal faces can reach 146. (4) Among those new minerals, silicates take the first place in number, followed by native elements, alloys, and then oxides. (5) The modes of occurrence of new minerals are varied, most of them occurring in oxidized zones of various deposits and deposits related to ma fic or ultramafic rock masses. There are a few new minerals occurring in skarn and placer deposits or even in cosmic dusts and meteorite.(6) The new minerals are characterized by wide but uneven distribution. Till now, new minerals have been discovered in 20 provinces or autonomous regions, especially in Hebei, Qinghai, Inner Mongolia and Henan. The number of new minerals found in North China is larger than that found in South Chine. (7) The number of discoverers of new minerals is in tens. The first discoverer of new mineral is Prof. Huang Yunhui, whereas Prof. Yu Zuxiang is the one who discovered the most numerous new minerals in China, totally disclosing 11 new minerals by himself or together with other experts. Most of the discoverers are members of the Chinese Academy of Geological Sciences, China University of Geosciences, and Institute of Geochemistry, Academia Sinica as well as other educational and scientific research institutions. The discovery of new minerals has promoted the development of mineralogy in China. Tens of discoverers were awardees of the National Natural Sciences Prize or the Science and Technology Progress Prize of the Ministry of Geology and Mineral Resources for the discovery and research results of new minerals in 1980s. More than 60 new mineals discovered in China were collected by the Geological Museum of China, with some of them exhibited in the Minerals and Rocks Exhibiting Room.

Abstract:

Indosinian S-type granites are widely distributed in central Inner Mongolia on the northern margin of North China landmass. Spread in nearly EW direction, the granites have formed a gigantic compound granite belt, with porphyritic biotite-admellite and moyite being the two main types. SiO2is abundant, Al2O3is 12.38%~15.34%. A/NKC (molecule ratio)>1.1, K2O/Na2O=1.1~3.1,δ=1.9~2.6,ΣREE is 45.778 ×10-6~486.501×10-6, andδEu=0.1~0.8. A series of zircon U-Pb surface ages (207~227 Ma) for the granites have been recently obtained from 1/50 000 regional geological survey. As the lithofacies and geochemical characteristics of the granites are similar to those of S-type granites, the authors conclude that the Indosinian granite in this area was formed in a post-collision setting instead of in the setting of syn-collision between North China plate and Siberia plate.