A uniquely shaped impact structure,the Hailin impact crater,has been discovered in northeast China.The crater was formed on a granodiorite hillside and is an oval depression with asymmetric rim height and a maximum diameter of 1360 m.The bottom of the crater is filled by Quaternary sediments with large amounts of rock fragments underneath.The discovery of quartz planar deformation features in rock clasts on the crater floor provides diagnostic evidence for the impact origin of the structure.The shape of the crater is largely due to the impact having occurred on a ridge terrain.The impact event probably occurred in the late Cenozoic Era.The Hailin impact crater is the fourth confirmed Chinese impact crater.

The high pressure minerals were formed in association with the collision process of planets or high pressure and high temperature conditions in the deep Earth.They are of special geological significance in the study of Earth and planetary sciences.shock-metamorphic rocks(meteorites)are important sample sources for finding high pressure minerals.Up to now,high-pressure minerals found in the terrestrial impact craters include coesite,stishovite,reidite,diamond,lonsdaleite,akaogiite,riesite,TiO2-Ⅱ,maohokite and majorite.Their genesis is related to the mechanisms including the solid state phase transformation,crystallization from melt,and/or decomposition of mineral.Because of the complexity in types and compositions of rocks and minerals on the earth surface,the study of high-pressure minerals in the terrestrial impact craters which are treasure houses for high-pressure minerals has an important development prospective.

Selenium (Se) is a micronutrient that has attracted significant attention, because the threshold for human health is low. During soil surveys in China, large areas of low-Se soil were found, and this condition may increase the probability of people suffering from Se deficiency. A multi-purpose regional geochemical survey conducted in the Lou Shao basin of Hunan Province found abundant Se-rich soils in Lianyuan City. However, as the primary grain-producing area in Hunan Province, the key factors affecting the spatial distribution of soil Se in the cultivated land of Lianyuan City remain to be elucidated. Therefore, based on the data of 5516 topsoil samples (0–20 cm) of cultivated land in Lianyuan City, we used geostatistics, correlation analysis, and a Geodetector to explore the effects of geological conditions (strata), soil types, soil properties, and topography on the distribution of Se in soil. The results showed that (1) in comparison to cultivated land in the Chinese mainland, Japan, Belgium, and Sweden, the cultivated land in Lianyuan City exhibits higher Se contents, with Se-sufficient and Se-rich areas accounting for 9.74% and 88.96% of the total area, respectively; (2) the distribution of high-Se soil was consistent with that in the Longtan Formation, Dalong Formation, and Daye Formation; (3) organic matter (OM) showed a positive correlation with Se, while both the elevation and slope were negatively correlated with Se; (4) stratum had the most significant effect on the spatial variation in soil Se, followed by OM. Lianyuan City is a typical Se-rich area, and the high level of Se in soil reduces the risk of local residents suffering with diseases caused by Se deficiency. The synergistic effect of stratum and OM is the key factor influencing Se enrichment in soils. Moreover, low-lying flat areas are more conducive to the accumulation of Se. This study will help farmers to identify suitable Se-rich cultivation areas in order to increase the Se content in crops, thereby providing a valuable basis for improvements in human health and the optimization of agricultural strategies.

The south of Hunan is rich in low temperature geothermal water resources, yet their formation mechanism has not been well investigated. This study focused on the occurrence conditions of geothermal water and estimation the thermal reservoir temperature and the circulation depth of geothermal water in this area. The hydrogeochemical analyses of 23 geothermal water samples are proceeded with the help of Origin, PHREEQC and Aquachem software. The results show that the main hydrochemical type of geothermal water in the study area is HCO 3 ·SO 4 –Ca·Mg and HCO 3 –Na. The δD and δ 18 O of the geothermal water samples show a linear right-up trend, indicating the geothermal waters were recharged by meteoric water. The mineral saturation index was calculated by PHREEQC, which indicated that the quartz and chalcedony minerals were close to the saturation state. The reservoir temperature range of geothermal water is estimated to be 38–122°C by using a silica (quartz) geothermometer, with an average of 73°C. The geothermal water circulation depth range calculated by the geothermal gradient is 1–4 km, with an average of 2.13 km.

Heavy metals with a high concentration value in the soil are detrimental to the soil ecosystem. In this study, 96 samples were taken from two soil sections (A-A, B-B) in the mouth of the Juanshui River to analyze heavy metal pollution. Soil pollution status and the ecological risk were investigated using Nemerow and the potential ecological risk index. The sources affecting pollution and pollution distribution characteristics were exhibited based on Inverse Distance Weighted (IDW), principal component analysis (PCA), and Statistics. Pollution in the soil of the mouth of the Juanshui River had reached a moderate level. Hg and Cd were the main potential ecological risk contributions. Coal burning and agricultural chemicals were the predominant pollution source in the study area. In order to avoid the soil of the river mouth becoming a secondary pollution source for water bodies and resulting in a vicious circle of heavy metal pollution, heavy metals in the soil of the river mouth of China should be mainly managed and controlled.

Impact breccia is a unique rock type that formed during the meteorite impact process and it is an ideal sample for the studies on the formation process of impact crater, dating impact craters, and shock effects in minerals and rocks. The Xiuyan impact crater is a simple crater with a diameter of 1800m and large amount of impact breccia in it. Here we mainly document the petrology and shock metamorphism of impact breccias from the Xiuyan impact crater through optical microscope, universal-stage microscope, electron probe microanalysis, X-ray fluorescence, and inductively coupled plasma mass spectrometry and then discuss their formation process and the morphology of impact crater. There are three types of impact breccia in the Xiuyan impact crater, which are the basaltic breccia and the polymict lithic breccia from the upper part of impact breccia lens, and the melt-bearing breccia at the bottom. The clasts in the basaltic breccia and the polymict lithic breccia are weakly shocked and only some quartz grains display planar deformation features which indicate shock pressures less than 20GPa. In contrast, the clasts in the melt-bearing breccia are strongly shocked, in which silicate glass, quartz planar deformation features, coesite, silica glass, diaplectic feldspar glass, reidite are observed, which indicate a shock pressure > 50GPa. This study confirms that the melt-bearing breccia is usually produced at the bottom of simple impact craters and is formed by mixing rock clasts collapsed from the transient crater rim and wall with shock melt at the bottom. The true depth of Xiuyan impact crater is 495m, and the true depth/diameter ration is 0. 275, which is consist with other simple impact craters. The central thickness of impact breccia lens is 188m and the thickness/diameter ration is 0. 104, slightly lower than that of other simple impact craters, which may be due to less rock clasts collapsed into the crater in the modification stage that caused by hilly terrain.

球粒陨石中的富Ca、Al包体(简称CAIs)主要由一些富Ca、Al的硅酸盐和氧化物(如尖晶石和黄长石等)组成,是目前已知的太阳系最古老的固体物质(4567.2±0.6 Ma;4567.30±0.16 Ma);球粒的矿物组成以镁铁质硅酸盐(如橄榄石和低Ca辉石等)为主,明显经历过熔融结晶过程.CAIs及其构成矿物具有最富16O的同位素组成特征,并在氧同位素δ17O-δ18O图解上构成一条斜率接近1的直线,这条直线常称为碳质球粒陨石无水矿物线(简称CCAM线).镁铁质硅酸盐球粒一般具有贫16O同位素组成特征.

The new Cuban chondrite, Viñales, fell on February first, 2019 at Pinar del Rio, northwest of Cuba (22°37′10″N, 83°44′34″W). A total of about 50–100 kg of the meteorite were collected and the masses of individual samples are in a range 2–1100 g. Two polished thin sections were studied by optical microscope, Raman spectroscopy and electron microprobe analysis in this study. The meteorite mainly consists of olivine (Fa 24.6 ), low-Ca pyroxene (Fs 20.5 ), and troilite and Fe-Ni metal, with minor amounts of feldspar (Ab 82.4-84.7 ). Three poorly metamorphosed porphyritic olivine-pyroxene and barred olivine chondrules are observed. The homogeneous chemical compositions and petrographic textures indicate that Viñales is a L6 chondrite. The Viñales has fresh black fusion crust with layered structure, indicating it experienced a high temperature of ∼1650°C during atmospheric entry. Black shock melt veins with width of 100–600 μm are pervasive in the Viñales and olivine, bronzite, and metal phases are dominate minerals of the shock melt vein. The shock features of major silicate minerals suggest a shock stage S3, partly S4, and the shock pressure could be >10 GPa.

We report the petrology and oxygen isotopic composition,using a Cameca Nano SIMS 50L ion microprobe,of a plagioclase–olivine inclusion,C#1,found in the Ningqiang carbonaceous chondrite.In addition to major phases（plagioclase,spinel and olivine）,C#1 is also surrounded by a pyroxene rim （64 vol%Ca-rich and 36 vol%Ca-poor pyroxenes）.On a three-isotope oxygen diagram,δ 17 O vs.δ 18 O,the compositions of individual minerals analyzed in C#1 fall along the carbonaceous chondrite anhydrous mineral line （CCAM）,and oxygen isotopic compositions in C#1 show significant variability in δ 18 O and δ 17 O.The oxygen isotopic compositions of the pyroxene rim minerals are similar to those of the other host minerals,which suggests that the rim likely formed from the same melting process as the host.The rim is considered to have formed as a result of interaction between an 16 O-poor gas and a melt.Some spinel grains are typically 16 O-rich and likely of relict origin,which is similar to 16 O-rich Ca-,Al-rich inclusions,which are probably a precursor of C#1.The inclusion then likely melted in an 16 O-poor region where chondrules form,accompanied by oxygen isotope exchange with an 16 O-poor gas.Some anorthite,pyroxene and spinel might have undergone fluid-assisted thermal metamorphism on the Ningqiang chondrite parent body.The oxygen isotope data and evolution of the C#1 plagioclase–olivine inclusion are similar with those of Al-chondrules in chondrites.

Coesite embedded in silica glass in suevite from the Xiuyan crater has been studied by scanning and transmission electron microscopy to better understand the mechanisms at formation of coesite. Coesite grains in this study mainly occur as vein‐like aggregates (10–40 μm in width) and irregular aggregates (IAs; <40 μm in size). Both aggregate types are composed of subhedral to anhedral coesite crystals with random orientations. Most of the crystals are 100–1000 nm in size, and some display twinning. The shape, twinning, and random orientation of coesite crystals suggest rapid crystallization in amorphous silica that became supercooled. The center of vein‐like aggregates crystallized from localized silica melt within diaplectic silica glass, whereas the rim of vein‐like aggregates and IAs crystallized from diaplectic silica glass. The size and amount of coesite crystals in the vein‐like aggregate vary greatly from the rim to the center of such veins. Microstructures suggest that the crystals nucleated heterogeneously at the outer rim of the vein and nucleated homogeneously within the vein. IAs do not show any changes in size and amount of coesite crystals from the rim to core of such aggregates. Coesite crystals in IAs primarily nucleate heterogeneously in diaplectic silica glass. It can be concluded that vein‐like coesite aggregates are mainly formed by crystallization from silica melt, and irregular coesite aggregates should be formed by solid‐state transformation of diaplectic silica glass.

“矿物学”是地质类专业的核心专业课程，是研究矿物的物理性质、化学性质、晶体结构、自然分布和状态的一门学科。“矿物学”课程的教学质量，直接关系到后续晶体光学、岩石学、矿床学等主干专业课的教学效果。众所周知，美国的高等教育质量在全球处于领先地位。亚利桑那州立大学整体实力在美国处于中上水平，是一个特色鲜明的强校，其地球与行星科学在全美处于靠前的位置。本文对亚利桑那州立大学的“矿物学”本科课程进行了详细介绍，并剖析研究了其教学特点，以期能为我国高校的相关课程教学提供一定的经验和借鉴。

陨石坑是固体星球表面最常见的地质构造.陨石坑在厘定星体表面年龄、地球地质历史上的灾变事件、矿物岩石冲击变质等研究中具有不可替代的作用.陨石撞击过程具有高温高压的特点,能在矿物岩石中留下独特的标志,从而为判定陨石坑提供依据.地球上识别陨石坑的线索可以分为地貌标志、矿物岩石标志和地球化学标志3大类,但只有矿物岩石中的冲击变质特征才能最终判定是否是陨石坑.迄今为止,地球上已发现190余个陨石坑,其中174个发育了冲击变质特征.文章首先介绍了陨石坑的类型和形成过程,然后详细论述了陨石坑的判别标志,最后总结了国内的陨石坑研究现状.

Feldspar is the most abundant mineral in the Earth’s crust and is widely distributed in rocks. It is also one of the most common minerals in meteorites. Shock-metamorphic features in feldspar are widely used to calibrate the temperature and pressure of shock events and can also provide clues for searching for impact craters on Earth. In this study, shocked alkali feldspars in the lithic breccia and suevite from Xiuyan Impact Crater were investigated using polarizing optical microscopes, Raman spectroscopy and electron microprobes to better constrain the shock history of this crater. For this study, feldspar grains occurring in gneiss clasts in the impact breccia and four shock stages were identified, e.g., weakly shocked feldspar, moderately shocked feldspar, strongly shocked feldspar, and whole rock melting. According to the shock classification system for alkali feldspar and felsic rocks, we estimated the shock pressure (SP) and post-shock temperature (PST) histories of these gneiss clasts. Weakly shocked feldspars display irregular fractures and undulatory extinction, and their shock stage is F-S2, which indicates that SP and PST are from ~5 to ~14 GPa and ~100 °C, respectively. Moderately shocked feldspars show planar deformation features and are partially transformed into diaplectic glass, which indicates that the F-S5 shock stage of SP and PST is from ~32 to ~45 GPa and 300–900 °C. Strongly shocked feldspars that occur as vesicular glass indicate a shock stage of F-S6, and the SP and PST are 45–60 GPa and 900–1500 °C, respectively. The whole felsic rock melting occurs as mixed melt glass clast and belongs to the F-S7 stage, and SP and PST are >60 GPa and >1500 °C, respectively.

Aluminum-rich chondrules are one of the most interesting components of primitive chondrites, because they have characteristics in petrography and mineralogy that are similar to both Ca- and Al-rich inclusions (CAIs) and ferromagnesian chondrules. However, their precursor and formation history remain poorly constrained, especially with respect to their oxygen isotopic distributions. In this study, we report on the petrography, mineral chemistry, and oxygen isotope ratios of two Al-rich chondrules (K1-CH1 and K2-CH2) in the Kainsaz (CO3) carbonaceous chondrites. The major phases in Kl-CH1 are plagioclase, olivine and Ca-poor pyroxene, and those in K2-CH2 are plagioclase and olivine. All minerals in two Al-rich chondrules are O-16-poor. The Delta O-17 values in K1-CH1 vary in two ranges of from -11. 1 parts per thousand to -8. 7 parts per thousand and from -3. 9%o to 0. 4 parts per thousand, while those in K2-CH2 vary from -6. 6%o to -0. 6%o with a tendency increasing from the core to rim. These observations provide a strong indication that the two Al-rich chondrules formed by the melting and crystallization of a mixture of materials from CAIs and ferromagnesian chondrules. The precursor materials of K1-CH1 and K2-CH2 are CAIs + olivine-pyroxene-rich chondrules and CAIs + olivine-rich chondrules, respectively. The O-16-poor isotopic compositions of all components in two Al-rich chondrules can be explained by oxygen isotopic exchange between the melt and O-16-poor nebular gas (Delta O-17: - 8. 7 parts per thousand - 7. 8 parts per thousand) during melting in chondrule-forming regions; whereas the minerals in two chondrules could have experienced further oxygen isotopic exchange with a relatively O-16-poor reservoir (Delta O-17: -0. 6 parts per thousand similar to 0.4 parts per thousand) on the parent body, likely during fluid-assisted thermal metamorphism.

CRATER. Feng Yin, Ming Chen, Thomas Sharp, Department of Geology, Hunan University of Science and Technology, Xiangtan, China 411201 (yinfeng@hnust.cn), Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China 510640, School of Earth and Space Exploration, Arizona State University, Tempe AZ, USA 85287-1404.

Introduction: Coesite, a common high pressure mineral with chemical composition of SiO2, is widely distributed in metamorphic rocks, meteorites, and impact craters. Coesite was firstly found in Meteor crater by Chao et al. [1] and was explained to be formed via a polymorphic transformation of quartz. So far, coesite had been reported in more than 30 impact craters and were considered as a result of solid-state transformation of amorphous silica [2] or crystallize from silica melt [3]. There are many coesite in silica glasses of the suevite from the Xiuyan crater. Chen et al. [4] proved these coesite crystallized from silica melt based on the morphology and occurrence of coesite. Here, we summarize the further investigations of the microtextures of coesites with different occurrences in the Xiuyan crater. Sample and Methods: A sample of suevite was collected from the drill cores of Xiuyan crater. Thin sections of the suevite were investigated using a combination of polarized and reflected light optical microscopy to document shock metamorphic features of minerals. And then Raman spectroscopy was used to verify the high pressure phases. We followed these investigations with field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) to characterize the microtextures of coesite in the suevite. Results: The suevite consists of fragments of gneiss, amphibolite, silicate glass and fine-grained matrix. Gneiss clasts are strongly shocked and are composed of silica glass, vesicular feldspar glass, and opaque black patches. Most silica glasses keep the same morphology as primary quartz, and some silica glasses display round outline. There are many coesite grains in the silica glasses and they mainly occur in two kinds of occurrence. One is the stringer of coesite that the average width is about 20 μm. The stringer always extends across most or all of the silica glass. The other is the granular coesite with a diameter up to 30 μm that are randomly distributed within the silica glass.. TEM images reveal both stringer and spherulite are indeed polycrystalline aggregates of coesite microcrystal. In the stringer, individual coesite microcrystal ranges from 100 to 500 nm and coesite crystals distribution is denser in the rim than that in the core (Fig. 1). In the spherulite, most coesite microcrystals aggregate and isolated coesite crystals are rare (Fig. 2). Discussion: Occurrences of coesite assemblages in the silica glass undoubtedly indicate they crystallize from silica melt. Phase diagram for SiO2 [5] indicates the pressure for coesite crystallization is 4.5-13 GPa.

The Xiuyan crater is a simple bowl-shaped crater 1800 m in diameter.Through a core drilling at the center of the crater,a small amount of siderite breccia was found at the top of the impact breccia unit that is covered by Quaternary lacustrine sediments of 107 m thick.The siderite breccia is composed of microcrystalline siderite and clasts of rocks and minerals.Carbon isotope analyses of the siderite exhibit extremely high δ13C values(+13.76‰ versus V-PDB).The age of siderite formation is about 37000 years ago,which is later than that of lacustrine sediments(39000–50000 years ago) and that of the impact event(50000 years ago).Positive δ13C excursions in siderite are mainly explained by carbon isotopic discrimination between carbonate and organic carbon due to methanogenic bacteria decomposing organic matter in a reducing environment.The siderite should be formed by deposition.The deposited siderite cemented clasts of rocks and minerals in impact breccias,which formed the siderite breccia.

The Xiuyan crater is a simple bowl-shaped crater 1800 m in diameter.Through a core drilling at the center of the crater,a small amount of siderite breccia was found at the top of the impact breccia unit that is covered by Quaternary lacustrine sediments of 107 m thick.The siderite breccia is composed of microcrystalline siderite and clasts of rocks and minerals.Carbon isotope analyses of the siderite exhibit extremely high δ13C values(+13.76‰ versus V-PDB).The age of siderite formation is about 37000 years ago,which is later than that of lacustrine sediments(39000–50000 years ago) and that of the impact event(50000 years ago).Positive δ13C excursions in siderite are mainly explained by carbon isotopic discrimination between carbonate and organic carbon due to methanogenic bacteria decomposing organic matter in a reducing environment.The siderite should be formed by deposition.The deposited siderite cemented clasts of rocks and minerals in impact breccias,which formed the siderite breccia.

<正>角砾岩是由未被磨圆的砾石经胶结而形成的碎屑岩。角砾岩可以形成于多种地质过程中,如沉积角砾岩、火山角砾岩、构造角砾岩以及撞击角砾岩等。与陨石坑研究有关的是撞击角砾岩。撞击角砾岩按照岩石特征,又可以分为石质角砾