Abstract:

From the different distribution areas of the Sijizhuang Formation at the bottom of the Hutuo Group, one sample of orthoclase granite-porphyry and one sample of porphyritic monzogranite gravels were selected, along with one sample of orthoclase granite-porphyry intruded into the Sijizhuang Formation in Jiangcun area. Zircon U-Pb-Hf isotope analysis was conducted. The weighted average ages of the orthoclase granite-porphyry and the porphyritic monzogranite gravel were determined to be 2 507±14 Ma and 2 519±35 Ma, respectively, indicating that the sources of the granite gravels were likely the late Neoarchean Ekou granite and Lanzhishan granite. The zircon ²⁰⁷Pb/²⁰⁶Pb age of the orthoclase granite-porphyry intruded into the Sijizhuang Formation was determined to be 2 157±15 Ma. Combining the ages of the Sijizhuang Formation and the Gaofan Group volcanic rocks in the Wutai area, and the geological events in the North China Craton from 2.2 to 2.0 Ga, it is inferred that the lower boundary of the Hutuo Group is likely to be 2.2 to 2.18 Ga, and its upper boundary age is approximately 2.0 Ga. The depo- sition process represents a period of intense intracontinental rift setting. The Hf isotope results of the Neoarchean granite gravel and the Paleoproterozoic granite zircons indicate that there was strong crustal growth in the early Neoarchean and crustal growth also existed in the late Neoarchean in the Wutai area.

Abstract:

The Qujia gold deposit is located in the central part of the Jiaojia gold metallogenic belt, which is an important concentrated area of altered-type gold deposits in China. The elevation of the deposit ranges from -726 m to -1 334 m. To study the evolution of pyrite and its indicative role in gold mineralization processes, in-situ trace element analysis of pyrite was conducted using LA-ICP-MS. The pyrites were categorized through petrographic observation and cluster analysis. It is revealed that trace elements such as Co, Ni, and As in pyrite mainly in the form of isomorphism, while elements such as Au, Ag, Cu, Zn, Pb, and Bi predominantly exist as mineral inclusions at the nano- and micron-scale. Pyrite is classified into five main types: Co-rich Py1, Ni-rich Py2, Au- and As-rich Py3, Au-, Ag-, Pb-, and Bi-rich Py4, and "clean" Py5. The trace element characteristics of pyrite indicate that ore-forming materials may have primarily originated from Precambrian metamorphic basement rocks and Mesozoic magmatic rocks, with a lesser contribution from the mantle. Ore-forming hydrothermal fluids likely resulted from a complex mix of metamorphic hydrothermal fluids, magmatic hydrothermal fluids, and shallow atmospheric precipitation. The different types of pyrite reflect the evolution of ore-forming hydrothermal fluids from Co- and Ni-rich to As- and Au-rich, and finally to Pb-, Bi-, Au-, and Ag-rich compositions. After the formation of Py1 and Py2, intense tectonic activities caused significant disturbance and enhanced the adsorption of gold complex compounds onto fracture surfaces, promoting gold precipitation within the fractures. This process likely played an important role in gold enrichment and mineralization. Pyrite with low Co and Ni contents but high fragmentation levels, as well as elevated concentrations of Au, Ag, As, Pb, and Bi, is closely associated with mineralization. In addition, the content of Co and Ni in pyrite is high, the crushing is strong, and the content of ore-forming elements is high, which is the characteristics of pyrite formed in the early stage and transformed by the later mineralization.

Abstract:

Shamai tungsten deposit is a medium sized magmatic hydrothermal deposit located in Dong Ujimqin Banner of Inner Mongolia. The ore bodies mainly occur in biotite monzonite granite and biotite monzonite granite porphyry. In this study, the petrography, LA-ICP-MS zircon U-Pb chronology and petrogeochemistry of biotite monzonite granite and biotite monzonite granite porphyry are studied in order to clarify the genesis and age of the two rocks and provide further data for regional prospecting. The results show that the LA-ICP-MS zircon U-Pb ages of biotite monzogranite are 135.6±1.6 Ma and 136.3±1.8 Ma, and the biotite monzonite granite porphyry is 138.6±1.1 Ma. The main elements show they are peraluminous high potassium calc alkaline granite which are characterized by high SiO₂ (73.73%~78.23%), Na₂O+K₂O (7.56%~8.89%)and low MgO (0.09%~0.20%), CaO (0.51%~0.89%), TiO₂ (0.03%~0.12%). They are enriched in Rb, K, Th, U, and depleted in Sr, Ba, Nb, P, Ti, with strong negative Eu anomaly and high FeO^T content, FeO^T/MgO and FeO^T/(FeO^T+MgO) ratio indicating the characteristics of A-type granite. The zircon U-Pb age of the Shamai granite is consistent with the age range of the large-scale metallogenesis in eastern China. The tectonic environment discrimination diagrams indicate that it was formed in the extensional tectonics environment after the continental collision in the Yanshanian period, which is related to the lithospheric thinning of northern margin of the North China Craton.

Abstract:

On the basis of field profile and core observation, multiple methods such as thin section identification, scanning electron microscopy, and electron probe were used to conduct a detailed analysis of the occurrence characteristics and formation mechanism of authigenic chlorite in sandstone reservoir of the Qigu Formation in the Fudong slope area, providing the adjustment direction for the search for oil and gas reservoirs and development plans. The results indicate that the authigenic chlorite in the sandstone of the Qigu Formation reservoir in the study area exhibits three occurrence states under the microscope: liner-type, membrane-type, and filling-type, with liner-type being the main occurrence, and the corresponding reservoir properties are good; Authigenic chlorite is iron-rich chlorite, and the dissolution of tuffaceous debris and feldspar minerals, the transformation between clay minerals, and the flocculent precipitation formed by Fe dissolved in rivers are the important material basis for the formation of authigenic chlorite; Sandstones with large grain size and well sorting have high content of authigenic chlorites, which is helpful for forming and protecting of authigenic chlorite; Strong fluid dynamic is also an important controlling factor of authigenic chlorite formation; The occurrence states of chlorite in the Qigu Formation are similar, and different content of authigenic chlorite have a certain affection on the reservoir property and sensitivity.

Abstract:

The Triassic Baikouquan Formation in the the Junggar Basin has huge oil and gas exploration potential, but the reservoir sand body has poor physical properties and strong heterogeneity. The reason for the formation of high-quality reservoirs is not yet clear, and the understanding of diagenetic characteristics is vague, which limits the exploration and development of oil and gas in this area. Based on the core observation,thin section analysis, scanning electron microscopy and physical property analysis, the diagenesis and pore evolution of the reservoir from the Baikouquan Formation are analyzed in detail. The results indicate that the rock type of the Baikouquan Formation in the study area is mainly sandy conglomerate, and the reservoir can be divided into reservoir supported by sand and gravel and supported only by sand. The overall reservoir space is mainly composed of primary intergranular pores with poor physical property, belonging to the low porosity and low permeability type. The diagenetic stage of the reservoir is the middle diagenetic stage B. Based on quantitative analysis, it was found that compaction and cementation have a significant impact on the physical properties of the reservoir. The pore increasing ability of dissolution is controlled by the type of rock support, and has a significant impact on the pore increasing of reservoir rocks supported by sand and gravel, while it has a relatively poor impact on the pore increasing of reservoir rocks supported by sandy particles.

Abstract:

The Longtan Formation in the Dafang area of Northwest Guizhou is characterized by alternated shale, coal seams, and sandstones, with typical characteristics of marine-terrestrial transitional facies. On the basis of profile measurement and sample collection, combined with XRD analysis of whole rock and clay minerals, determination of total organic carbon (TOC) measurement, rock pyrolysis, kerogen macerals, and vitrinite reflectance (R_O) analysis, the development characteristics of hydrocarbon source rocks of the Longtan Formation in the study area are studied and evaluated. The results indicate that: ① The minerals in the rocks of the Longtan Formation are mainly clay minerals with strong adsorption capacity, but there is a significant negative correlation between clay mineral content and quartz content (R>0.8), especially the clay content of over 70% in shale and the lower brittleness index, which is very unfavorable for fracturing development; ② The abundance of organic matter in the Longtan Formation is significantly controlled by lithology. The coal seam has the highest TOC content (average 42.9%) and hydrocarbon generation potential (average 2.68 mg/g), indicating strong hydrocarbon generation potential of coalbed methane; The hydrocarbon generation potential of shale is less than 2 mg/g, but about 80% of the samples have TOC content exceeding 2%, and the shale gas resource potential is less than that of coalbed methane; Silty sandstone has the worst hydrocarbon generation potential, with an average hydrocarbon generation potential of 0.13 mg/g and a TOC content of 1.4%~5.6%, indicating a certain degree of tight gas potential; ③ The macerals of the Longtan Formation kerogen are mainly composed of liptinite and vitrinite, with type Ⅲ kerogen being the main type and type Ⅱ₂ being the auxiliary type. They have a high degree of thermal evolution and are in the stage of high-over mature dry-gas generation; ④ The middle section of the Longtan Formation, where coal seams are more developed, is a favorable zone for joint exploration of coalbed methane, shale gas, and tight sandstone gas in the Dafang area.

Abstract:

Strontium isotopes have become one of the effective tools for studying and comparing global geological events such as global sea level changes, orogeny, paleoclimate, and paleoenvironment. This article takes the field profiles and drilled cores of Early and Middle Triassic evaporites in the eastern region of Sichuan Basin as the main research objects, tests the strontium isotope compositions of carbonate rocks, sulfate rocks, and halite rocks, and establishes the corresponding strontium isotope evolution curves. The results show that the average ⁸⁷Sr/⁸⁶Sr value of carbonate rocks is 0.707 895, the average ⁸⁷Sr/⁸⁶Sr value of anhydrite rocks is 0.708 174, and the average ⁸⁷Sr/⁸⁶Sr value of halite rocks is 0.708 177, and the ⁸⁷Sr/⁸⁶Sr value of carbonate rocks increased rapidly from 0.707 413 in the Early Triassic to 0.708 515 in the early Middle Triassic, and then showed a downward trend. Overall, the ⁸⁷Sr/⁸⁶Sr values are close to the published global ⁸⁷Sr/⁸⁶Sr data of the same period in the Early and Middle Triassic, indicating that the material source of the Early and Middle Triassic potassium salt in the eastern region of the Sichuan Basin is mostly seawater and deposited in a marine sedimentary environment. At the same time, the greenhouse effect caused by volcanic activity also provides climatic conditions for potassium salt deposition.

Abstract:

Volcanoes are a window for humans to explore deep magma systems. From a global perspective, crystal-poor and melt-rich volcanic rocks (especially basalt and rhyolite) are mainly exposed all over the earth, while crystal-rich felsic volcanic rocks exposed around many calderas. The felsic crystal-rich volcanic rocks can be mainly divided into two types: one type is the volcanic rocks with homogenous composition and crystal contents; the other type is the volcanic rocks with zoned composition and crystal contents. The crystal-rich volcanic rocks erupted due to the cold stored crystal mush was remelted, reactivated, and remobilized after being repeatedly recharged by hot magma. The composition of the preexisting materials in the reservoir constrained the type of crystal-rich volcanic rocks formed by reactivation. The existence of crystal-rich volcanic rocks can well explain the contradictory phenomenon that the magma reservoir has a long life, but the process of magma accumulation and crystallization is rapid. Although the research of felsic crystal-rich volcanic rocks has made obvious progress in recent years, there are still many problems to be solved, such as the origin of porphyritic lava, how to reveal the reactivation of crystal mush, the relationship between crystal mush reactivation and volcanic eruption, the time scale of magma recharge and crystal mush reactivation, etc. Further research on crystal-rich volcanic rocks will promote the understanding of the mechanisms of melt evolution, migration, and shallow accumulation and eruption, providing more information for establishing a more comprehensive model of felsic magma evolution.

Abstract:

By segmenting the sand sample image into single particles and identifying its components, the accuracy and efficiency of sand sample lithology analysis can be significantly improved. The existing methods for sand sample image segmentation mainly rely on traditional watershed algorithms and convolutional neural networks, but due to insufficient extraction of details from single particle rock debris contours, the mis-segmentation rate is high. Therefore, this paper proposes a single particle image segmentation and extraction method that combines convolutional neural networks and watershed algorithms, using image fusion algorithms as a bridge. Firstly, an improved Mask R-CNN network is used to quickly segment the original sand sample image and obtain its initial segmented image; Then, the initial segmented image is fused with the original sand sample image, and an improved watershed algorithm is used to segment the fusion results; Finally, using the coordinate point matching method of the original sand sample image, the resulting image obtained from watershed segmentation is corrected to complete the extraction of single particle rock debris images. The experimental results show that the accuracy of the single particle automatic segmentation and extraction method proposed in this paper is as high as 96.77%, and the model is lightweight and precise, providing a feasible and effective method for rock debris image segmentation, which can meet the needs of effectively calculating structural changes in oil reservoirs, searching for potential sediment sources, and dynamic changes of reservoirs.

Abstract:

TESCAN Integrated Mineral Analyzer (TIMA) is an analysis system based on a scanning electron microscope that incorporates multiple X-ray spectrometers and other detectors. It could automatically identify minerals and produce images. TIMA has been widely applied in earth sciences, including petrology, mineralogy, geochemistry, petroleum, and paleontology, particularly in the rapid analysis of some geological samples with complex mineral composition and structure and small grain size, and a large number of repetitive samples to obtain statistical data for research purposes. In order to achieve the goals of analysis and save costs, it is crucial to select the optimal analytical conditions, but this aspect is often overlooked. This article takes sample of gold-bearing pyrite-sericite-quartz altered rock from the Huachanggou gold deposit in Lueyang County, Shaanxi Province, as an example. Using TIMA, the samples were analyzed under different scanning modes, analysis types, and various experimental parameter settings. The study compared the mineral phase composition data, image quality of mineral phase maps and elemental distribution maps in a small field, as well as statistical data such as mineral grain size. The results indicate that the main factors influencing the quality of TIMA analysis are the backscattered electron (BSE) pixel spacing, energy-dispersive X-ray spectroscopy (EDS) test dot spacing, and X-ray acquisition counts. The selection of analytical conditions primarily depends on the mineral composition, mineral grain size, and the purpose of the analysis.

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 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:

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:

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:

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:

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:

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:

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:

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:

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.

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.