Abstract:

Mesoproterozoic magmatic rocks are extensively exposed along the southwestern margin of the Ordos Basin. Relevant studies are of great significance for revealing the breakup process of the Columbia Supercontinent. To clarify the magmatic genesis and the tectonic evolution characteristics of this era, this paper conducts systematic petrological, zircon U-Pb geochronological, and geochemical studies on the bimodal igneous rocks in the Qi'angou area of the southwestern Ordos Basin. Zircon U-Pb dating results show that the ages of the granite porphyry and basaltic andesite are 1 794±10 Ma and 1 803±21 Ma, respectively, indicating their formation in the Mesoproterozoic. Geochemical characteristics reveal that the granite porphyry is a peraluminous A₂-type granite, enriched in largeion lithophile elements (LILE) and depleted in high field strength elements (HFSE), with relatively high Rb/Sr ratios (2.95~3.55), reflecting its origin from crustal melting.The basaltic andesite belongs to the calc-alkaline series, exhibiting island arc-type distribution characteristics of selective LILE enrichment and significant HFSE depletion, with right-inclined rare earth element (REE) distribution patterns. Compared with the continental crust, it has higher La/Nb (3.83~4.01) and La/Ta (342~355) ratios, indicating its derivation from the enriched lithospheric mantle and influence of crustal material contamination (Nb/Ta=17.8~18.6, obvious Rb-Th enrichment). The insignificant Eu anomaly (δEu=0.96~0.97) suggests that the magma did not undergo obvious plagioclase fractional crystallization during its evolution.Comprehensive analysis based on tectonic discrimination diagrams and regional tectonic settings indicates that this set of bimodal igneous rocks formed in a post-orogenic intracontinental extensional environment during the Mesoproterozoic, reflecting the breakup event of the North China Craton around 1.80 Ga.

Abstract:

Based on the 1∶50 000 regional geological and mineral survey in Jianshui area of Yunnan Province, a set of pillow lava was determined in the study area, which was scattered on the Triassic clastic rock strata. The weighted average age of 14 zircons obtained by LA-ICP-MS zircon U-Pb dating is 352.3±5.9 Ma (MSWD=1.7), which belongs to the early period of Early Carboniferous and represents the eruption time of lava. The lava has the characteristics of high alkali (Na₂O>K₂O, Na₂O/K₂O=2.93～65.7, average 23.1), high Al(Al₂O₃=11.43%～16.67%)and low Ti(TiO₂=1.71%～2.62%,average 2.16%). It belongs to the subalkaline basalt series. The total amount of rare earth elements of the lava is low, ∑REE = 101.81×10^-6~138.50×10^-6, and it is enriched in large ion lithophile elements such as Rb, Ba, Th, K and high field strength elements such as Nb, Ta, etc., showing the characteristics of the large uplift distribution pattern unique to the intraplate basalt, which is similar to the characteristics of OIB. The normalized rare earth element distribution pattern of lava shows a right-leaning distribution pattern enriched in light rare earth elements, which is similar to the characteristics of intraplate basalt or oceanic island basalt. Combined with the regional geological background, this paper believes that the Jianshui pillow lava may be a product of the Yangtze and Cathaysian continental blocks controlled by the Paleo-Tethys multi-island ocean system under the early extension of the Late Paleozoic, along with the basic volcanic rocks in the northern section of Shizong-Mile, and the Early Carboniferous pillow basalts in the Longlin area of Jingxi, western Guangxi.

Abstract:

The Late Neoarchean witnessed a significant compositional transition of the continental crust in the North China Craton from sodium-rich to potassium-rich, marking a key stage of crustal maturation. However, the precise timing and processes of this transition remain unclear. In this study, we present an integrated analysis of petrography, geochemistry, zircon U-Pb geochronology, and Lu-Hf isotope for Late Neoarchean sodium-rich and potassium-rich granites from the southwestern Zhongtiao Mountains. The purpose of this study is to constrain their formation ages and source characteristics, and to explore their dynamic background and implications for continental crust maturation. Zircon U-Pb dating indicates that both the trondhjemitic gneiss and the monzogranite were formed in the late Neoarchean, with crystallization ages of 2 531±18 Ma and 2 527±54 Ma, respectively. Whole-rock major and trace element data, together with zircon Lu-Hf isotopes, suggest that the trondhjemitic gneiss was mainly formed by the partial melting of the mafic rocks in the lower crust in the early Neoarchean, while the monzogranites were primarily derived from partial melting of ancient high- to medium-K basaltic lower crust, with a minor contribution from metasedimentary rocks (mainly graywacke). Combined with regional geological evidence, we propose that the diverse Late Neoarchean granitoids in the Zhongtiao Mountains were generated by partial melting of sources at different crustal depths, including mafic lower crust, and minor metasedimentary rocks, likely triggered by mantle plume activity. The emplacement of the potassium-rich granite at ~2.53 Ga signals crustal maturation in this region, reflecting the stabilization of the local continental crust.

Abstract:

This study presents a systematic petrological, LA-ICP-MS zircon U-Pb geochronological, and whole-rock geochemical investigation on the Neoproterozoic augen- and granitic gneisses from the Wenquan Group, West Tian-shan. Results show that these granitic gneisses crystallized at 904.5±4.1 Ma to 902±4 Ma, representing an early Neoproterozoic magmatic event. The rocks are characterized by high silica (SiO₂ = 65.23%~68.75%), high alkali (ALK=7.46%~8.89%), high potassium (K₂O/Na₂O = 1.01~2.24), and strong peraluminous affinity (A/CNK= 1.05~1.18), belonging to the high-K calc-alkaline series and typical S-type granites. They are enriched in Rb, Ba, Th, and light rare earth elements (LREE), depleted in Nb, Sr, Ti, and P, and exhibit moderate negative Eu anomalies. Comprehensive analysis indicates that the magmas were derived from high-temperature dehydration melting of greywacke with minor pelitic rocks from the Paleoproterozoic Wenquan Group, and formed in a syn-collisional tectonic setting related to the Grenvillian orogeny during the assembly of the Rodinia supercontinent. This study provides precise geochronological and geochemical constraints on the Precambrian basement of the Yili Block and offers important insights into the tectonic affinity between the Yili Block, the Central Tianshan Block, and the Tarim Craton.

Abstract:

Carbonate reservoirs play a pivotal role in petroleum exploration endeavors within the Tarim Basin. However, due to limited core sampling, severe dolomitization, and challenges associated with conventional well logging interpretation, the classification and correlation of Cambrian-Ordovician carbonate strata have long remained contentious. Stable carbon isotopes offer a promising avenue for facilitating global or basin-scale stratigraphic correlation, thereby presenting a novel approach to addressing this issue. This study systematically investigates the carbon and oxygen isotopes of 116 carbonate samples sourced from the Upper Cambrian to Lower-Middle Ordovician in Well GC8, situated in Gucheng area, Tarim Basin, NW China. The results show that the distribution of δ¹³C values ranges from -2.32 ‰ to +0.53‰, with an average of -0.95‰. The overall δ¹³C exhibits a negative trend from bottom to top with a small change in amplitude, typified by two cycles of gradual negative excursions succeeded by abrupt positive excursion. The δ¹⁸O values portray a predominantly negative trend with limited variability, characterizing by two weak positive excursions followed by strong positive excursions. Based on the conodont biostratigraphy, comparative analysis with other representative sections elucidates the presence of TOCE (top of Stage 10 isotopic carbon excursion), COTICE (Cambrian-Ordovician transition isotopic carbon excursion) and MDICE (mid-Darriwilian isotopic carbon excursion) through the Upper Cambrian to Lower-Middle Ordovician in Well GC8. Notably, the documentation of TOCE and COTICE excursions within the Tarim Basin represents a pioneering discovery, with potential implications for positioning the Cambrian-Ordovician boundary at the inflection point of δ¹³C positive excursion after the TOCE. Furthermore, regional disparities in the MDICE development across the Tarim Basin hint at potential sedimentary hiatus of the Yijianfang Formation in Well GC8, with likely exhibiting the absence of the Pygodus anserinus conodont zone and a substantial portion of the Pygodus serra conodont zone in the Yijianfang Formation in Gucheng area.

Abstract:

The Neoproterozoic strata in the southeastern North China Craton are primarily distributed in the western part of Shandong, the Xuzhou-Suzhou area, and the Huainan area, spanning several administrative regions and tectonic units. The coeval Neoproterozoic strata in these areas have been named differently within separate areas, which has created significant challenges for regional stratigraphic correlation. This has further hindered the comprehensive and systematic studies on the sedimentary environment evolution, paleogeographic patterns, and geothermal resource distribution in the southeastern North China Craton during the Neoproterozoic. Based on the historical stratigraphic classification and abundant data of specific stratigraphic sections, especially the field sections measured by this study, we establishes a stratigraphic correlation framework for the Neoproterozoic strata of the southeastern North China Craton. Through field-based lithological and sedimentary structural descriptions, combined with the microscopic identification of sedimentary components and textures, five sedimentary facies zones have been identified within the Neoproterozoic carbonate strata. They are Evaporitic facies, Platform interior restricted, Open marine, Platform-margin reef and shoals, and Carbonate ramp slope facies zones. The statistic of the carbonate strata thicknesses from various sections reveals that the relatively deep-water Platform-margin reefs and shoals facies zone are predominantly distributed in the southeastern part of the study area. Toward the western and northwestern parts of the study area, the depositional environment shallows progressively and Open marine and Platform interior restricted facies zones developed, accompanied by a gradual thinning of the strata. This facies zone transition reflects a Neoproterozoic paleogeographic pattern of low in southeast and high in northwest, with marine water transgressed from the southeastern part to the northwestern part of the study area. Based on the facies and paleogeographic analysis, and in combination with geothermal reservoir evaluation criteria, it can be inferred that the reef-shoal facies bearing Niyuan, upper Wangshan, and Jinshanzhai formations on the southern part of Huaibei, the dolostones bearing Sidingshan Formation on the northwestern part of Huainan, and the Platform-margin reefs and shoals facies zone bearing Jiuliqiao and Sidingshan formations on the eastern part of Bengbu have great potential for the development of karst geothermal reservoir. These findings provide targeted areas for future geothermal exploration and development.

Abstract:

In spodumene pegmatite veins, spodumene exhibits a distinctive spodumene-quartz intergrowth (SQI) texture. Studying its microstructure, textural characteristics, and genetic mechanism is of great significance for further revealing the metallogenic mechanisms of granitic pegmatite-type lithium deposits. This paper takes the Late Triassic to Early Jurassic spodumene pegmatite veins in the Lijiagou area, Markam, western Sichuan, as an example. By integrating optical microscopy, scanning electron microscopy, electron probe microanalysis, and electron backscatter diffraction, we investigated the mineral composition, major element geochemistry, and crystal-lographic orientation of the rocks. Combined with the regional geological background and previous research findings, this study provides the following preliminary insights into the formation mechanism of the SQI texture in the Lijiagou spodumene pegmatites in western Sichuan: ① The fine-grained spodumene within the SQI shows high consistency with the host spodumene in terms of major element composition and crystallographic orientation. Moreover, cleavage planes of the host crystal extend continuously into the SQI domains, indicating that both originally belonged to the same crystal and share identical compositional and structural features; ② The SQI did not form through magmatic-hydrothermal metasomatism or undercooling crystallization. Instead, early spodumene phenocrysts underwent brittle ductile deformation under regional tectonic stress, leading to shearing and fragmentation into fine-grained spodumene aggregates. Subsequently, siliceous melt infiltrated along the fracture systems and crystallized as quartz, ultimately forming the intergrowth texture; ③ The morphology of quartz is controlled by the interstitial spaces between spodumene grains and shows no obvious signs of deformation. It is interconnected with surrounding quartz, suggesting that its formation occurred after the syn deformational period, representing crystallization of siliceous melt within the interstitial gaps along spodumene grain boundaries. In summary, the spodumene-quartz intergrowth texture in the Lijiagou spodumene pegmatite veins formed under an orogenic compressional setting and is a deformation-induced product.

Abstract:

Rutile is one of the common solid inclusions in quartz crystals. In addition to existing as a single mineral inclusion, there is also a special growth phenomenon of the intergrowth of rutile and hematite forming "rutile star". This study investigates the crystallographic orientation relationship and formation mechanism of rutile inclusions within quartz crystals through various analytical techniques including optical microscopy, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and crystallographic structure analysis. The results indicate that the rutile inclusions in quartz crystal samples are either protogenetic or syngenetic inclusions. Microscopic observations revealed two distinct morphological types of rutile: one is the oriented arrangement of rutile with irregular bamboo-joint-like fractures, and the other is the elongated prismatic rutile growing with hematite as the core, forming a "rutile star" with an approximate 60° angle. Since the {100} or {010} plane nets of rutile are structurally similar to the {001} plane net of hematite, the {100} or {010} plane of rutile can be joined and grow with the {001} plane of hematite. There are two possible crystallographic orientation relationships for the intergrowth of rutile and hematite: the c-axis of rutile is parallel to the <210> direction of hematite, and the <101> direction of rutile is parallel to the <210> direction of hematite. The formation of "rutile star" inclusions originates from the parent hematite-ilmenite solid solution. As the temperature decreases, the solid solution decomposes into ilmenite and hematite. The Fe²⁺ in ilmenite is oxidized to Fe³⁺, resulting in the formation of hematite and rutile. The rutile nucleates perpendicular to the {001} planes of hematite and grows progressively along {001} planes of hematite, ultimately forming "rutile stars" with hematite as the core and rutile crystals intersecting at 60°.

Abstract:

Carbonatite-alkaline complex-associated rare earth element (REE) deposits are the principle sources of REEs. The enrichment and mineralization processes of REEs during such magmatic-hydrothermal systems are currently the most highly debated issues in metallogenic studies. Due to the widespread occurrence of bastnäsite and monazite in nature, most studies are focused on the mineralogical and geochemical properties of REE phosphates and fluorcarbonates. Unfortunately, experiment results demonstrate that the solubilities of REE phosphates and fluorcarbonates are insufficient for the formation of REE mineralizing fluids. By contrast, REEs also occur as Na-rich REE carbonate minerals in carbonatites, including carbocernaite and burbankite. These minerals are formed from some unique fluids, meanwhile easily altered during later hydrothermal processes, hence attracting limited research interests. However, according to the results from latest experiments, the transition from bastnäsite to carbocernaite via reacting with Na⁺ and CO^2-₃ is the essential process that leads to the exceptional enrichment of REEs in aqueous liquids. Furthermore, REEs precipitate preferentially as carbocernaite or burbankite from Na-enriched carbonate fluids, and crystallization of bastnäsite occurs either during a relatively early stage where Na is insufficiently enriched, or after Na precipitating substantially as alkaline silicate minerals during interaction with silicate wall rocks. These findings are consistent with REE occurring as burbankite in isolated systems (such as fluid inclusions), but as bastnäsite in carbonatite ore veins or other open systems, and indicate that such Na-rich REE carbonate minerals have clear implications for REE mobilization and mineralization processes. In this paper, we reviewed the crystal structures and chemical properties of carbocernaite and burbankite, and compared the occurrence of both minerals in carbonatite REE deposits to those in high pressure-temperature experiments, aiming to reveal the roles of such minerals during REE mobilization and mineralization processes, and provides clues for establishing a comprehensive REE metallogenic model in carbonatite systems.

Abstract:

Continental collisional orogens represent a critical component of Earth's deep carbon cycle, with their decarbonation processes exerting a profound influence on global carbon budgets and long-term climate evolution. In contrast to oceanic subduction zones, continental collision belts are characterized by higher geothermal gradients, more felsic (sialic) compositions, and weaker fluid activity. Their decarbonation mechanisms are dominated by metamorphic reaction-driven decarbonation and anatexis-induced carbon release. This contribution systematically reviews decarbonation mechanisms in continental collisional orogens, with a focus on thermodynamic modeling of Paleoproterozoic "hot" orogens (exemplified by the Khondalite Belt, North China Craton) to elucidate carbon cycling characteristics under early plate tectonic regimes. Modeling results reveal that high geothermal gradients promoted intense and rapid metamorphic decarbonation during the early prograde stage in Paleoproterozoic orogens, whereas Phanerozoic cold orogens experienced decarbonation predominantly during exhumation. Under high-temperature and fluid-present conditions, carbonate rocks may undergo partial melting (generating anatectic carbonatites). These carbonatitic melts are highly mobile, and their degassing during formation, ascent, and interaction with country rocks constitutes a significant pathway for carbon release. We propose that the widespread continental collisional orogeny and supercontinent assembly events in the late Paleoproterozoic, due to their elevated thermal regimes, may have triggered large-scale carbon emissions, profoundly influencing contemporary global carbon cycling and climate evolution. The associated carbon fluxes quantitative constraints are needed in future models.

Abstract:

The exhumation of geological bodies is a product of interactions among Earth's spheres. Precisely determining the timing and processes of exhumation has become a crucial aspect of modern Earth system science. Thermochronological techniques, particularly fission-track and (U-Th)/He dating, play a central role in this endeavor. Conventionally, for the same mineral type within a single rock sample, the fission-track age should be greater than or equal to the corresponding (U-Th)/He age. However, the phenomenon of the (U-Th)/He age appears older than the fission-track age, and significant dispersion of single-grain (U-Th)/He ages beyond analytical error are common yet often overlooked anomalies in low-temperature thermochronology. This paper aims to clarify potential misconceptions in interpreting thermochronological data and provides a concise yet systematic review of the interplay among factors such as the accumulation and annealing of radiation damage, the U-Th zonation, thermal history, and mineral chemical composition. These factors can significantly alter the annealing behavior of fission tracks and the diffusion behavior of ⁴He within crystals, leading to a decrease in the fission-track annealing temperature and an increase in the (U-Th)/He closure temperature, thereby resulting in age inversion. The dispersion of single-grain (U-Th)/He ages and the inversion between fission-track and (U-Th)/He ages often carry important geological information, providing key clues for interpreting complex thermal histories.

Abstract:

Natural pink diamonds have attracted significant attention due to their stunning color, complex geological background, and extreme rarity. Their main coloration mechanisms include the 550 nm absorption band (accounting for approximately 99%) and NV color centers (accounting for approximately 0.6%). The former is found in Type Ⅰa and Ⅱa diamonds, while the latter only exists in Type Ⅱa diamonds. Currently, there is no artificial method capable of simulating natural plastic deformation to introduce the 550 nm absorption band. However, NV color centers can be introduced through multi-stage treatments including HPHT, irradiation and annealing, which are used for color modification of natural diamonds (predominantly Type Ⅰa, supplemented by Type Ⅱa) and synthetic diamonds (Type Ⅰb-Ⅱa and Type Ⅱa). Additionally, NVH and SiV color centers are also found in some chemical vapor deposition (CVD) synthetic diamonds. This paper systematically compares the gemological and spectroscopic characteristics of natural pink diamonds, treated natural diamonds, and synthetic diamonds (produced by CVD or HPHT methods), and proposes a rapid identification method based on ultraviolet-visible spectroscopy (UV-Vis) and infraredspectroscopy (IR). Furthermore, comprehensive identification of pink diamonds is achieved by combining photoluminescence spectroscopy (PL) and DiamondView.

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:

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:

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:

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 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:

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:

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:

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:

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:

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:

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:

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.