Table of Content

20 April 2024, Volume 30 Issue 02

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Molecular Simulations on the Controls of Phase Transition of Ca-Mg-Ba-CO3 Amorphous Precursors by Dehydration: Comparative Study of Dolomite and Norsethite

CHEN Yan, ZHU Xiangyu, TENG Hui

2024, 30(02):  119-132.  DOI: 10.16108/j.issn1006-7493.2023019

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Dolomite, one of the most widely distributed carbonate minerals on the Earth’s surface, is abundantly developed in ancient strata, but rarely exposed in modern marine environments. After decades of research, few low-temperature experiments have been reported to successfully synthesize ordered dolomite. The mineralization behavior of dolomite is one of the most intriguing mysteries. Conventional wisdom theories that Mg²⁺ hydration is the critical limit for Mg²⁺ to enter carbonate lattice. However, a recent study unveiled evidence questioning this premise and instead indicated that the structural constraints in the relevant amorphous precursor phase may play a more important role. Because transformation and crystallization of amorphous precursor phase in solution is a likely crystallization pathway for dolomite formation, and dehydration may have a pivotal effect on this process. Therefore, we carried out a study using molecular dynamics simulations to study the phase transition and dehydration process of amorphous precursors in Ca-Mg-Ba-CO₃ systems. The results show that the density increases significantly during the dehydration process, but the distances between metal cations and other ions are little affected and the total coordination number is unchanged. In terms of translational dynamics, the diffusion behavior of amorphous precursors in hydrated Ca-Mg-CO₃ and Ba-Mg-CO₃ systems (i.e., ACMC and ABMC) are similar, but the particle of ACMC is less mobile, hindering the aggregation of nucleation clusters. Thermodynamically, there is a significant difference in the dehydration enthalpy between ACMC and ABMC systems, with ACMC system having a higher dehydration enthalpy and the difficulty in losing the last few H₂O molecule from the structure, presumably limiting dolomite crystallization. This study systematically addressed the role of dehydration in controlling the crystallization of dolomite and norsethite and the findings of this study may provide insight into the “dolomite problem”.

NaOH Alkaline Fusion Method for B Isotope Analysis of Silicates

LI Zhenghui, CAI Yue, WEI Haizhen, LI Ye, ZHANG Weiwei, LI Baichan

2024, 30(02):  133-141.  DOI: 10.16108/j.issn1006-7493.2023004

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Boron(B) isotope analysis is an important tool in the research of earth and planetary science. However, challenges still exist for precise and accurate measurements of boron isotope ratios of silicate material due to the challenges in sample digestion.
Alkaline fusion is a suitable sample dissolution method for boron isotope analysis in silicates. At present, alkaline fusion  methods require expensive platinum or glassy carbon crucibles as well as high flux-to-sample ratios. Additionally, the existing methods used for dissolving the fusion cake may cause boron loss. To achieve full dissolution and effectively prevent B loss, this study reports an improved alkali fusion method using sodium hydroxide and silver crucibles with a low flux-to-sample mass ratio of 5:1. Full dissolution was achieved through gentle heating in the presence of water combined with a stepwise dissolution procedure, which effectively prevented B loss during the dissolution of the fused alkaline cake. Using this improved procedure for dissolution, Amberlite IRA743 B-specific resin for B purification, and a multi-collector inductively coupled plasma mass spectrometer (MCICP- MS) for isotope analysis, we report boron isotope compositions and concentrations data for five silicate international standards. The results are consistent with the published data within analytical uncertainties. This safe and efficient method will greatly facilitate B isotope research of silicates.

Incorporation Mechanism and Solubility Control Factors of Water in Eclogite from Subduction Zone

YIN Changxin, KANG Lei, LIU Liang

2024, 30(02):  142-156.  DOI: 10.16108/j.issn1006-7493.2022098

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Eclogite, an important high-pressure metamorphic rock in subduction zone, mainly consists of garnet and omphacite which are known as nominally anhydrous minerals (NAMs). With the increasing temperature and pressure during slab subduction, the water-rich fluid is released, but garnet and omphacite in eclogite can still carry a certain amount of water and therefore become important carriers of water transporting to the interior of earth. During the exhumation of ultra-high pressure rocks, garnet and omphacite can release water as hydroxyl exsolution due to the decreasing pressure, which can consequently cause a series of important geodynamic processes such as retrograde metamorphism and even syn-exhumation magmatism. This paper summarized the analytical methods of water in minerals, the mechanism of water dissolved in garnet and omphacite, the controlling factors of water solubility (e.g., chemical composition, pressure, temperature, water fugacity, and oxygen fugacity) and the behavior of water in eclogite during slab subduction / exhumation. The future direction and key scientific problems are also prospected. 


Pyrophyllite Formation and Its Resource Implication in the Late Devonian Wutong Formation of Tongling Mineralization Cluster

LIU Tong, XIE Qiaoqin, XU Liang, WANG Jiayu, ZHOU Yuefei, CHEN Tianhu, XU Xiaochun

2024, 30(02):  157-164.  DOI: 10.16108/j.issn1006-7493.2023002

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Yeshan iron deposit is a small-scale Carboniferous syn-sedimentary hydrothermally overprinted deposit in the Xinqiao ore field, Tongling mineralization cluster. In this paper, systematic mineralogical research has been carried out on sedimentary
rocks of the Late Devonian Wutong Formation in Yeshan iron deposit using powder X-ray diffraction (XRD), scanning electron microscopy (SEM). Our results indicate that the dominant minerals in the Wutong Formation are detrital quartz and feldspar, and clay minerals including pyrophyllite, illite, and kaolinite, with some hematite and goethite. Higher average concentration of pyrophyllite in the studied Wutong sedimentary profile with from 7.54% to 70% occurs in the middle of the profile. Pyrophyllite in the samples shows micrometer scale euhedral to semi-euhedral block forms and grew around quartz particles. Pseudomorphic hexagonal prisms quartz particles consisting of lamellar pyrophyllite are also identified in the sedimentary rocks. The pyrophllite bearing ore compositions based on the XRF data show that the SiO2 content ranges from 44.47% to 80.23%, and Al2O3 from 10.49% to 28.75%. According to mineral assemblages and chemical compositions of the Wutong Formation sedimentary rocks from the Yeshan deposit, pyrophyllite bearing sedimentary rocks are proposed to be pyrophyllite ore and the ore belongs to silicaalumina pyrophyllite ores, which is an important raw clay mineral resource applied in the fields of ceramic raw material, refractory material, and alkali-free glass. The microstr uctures of the ore and the geological background of the mining area indicate that the pyrophyllite in the Wutong Formation may be the products of the reactivation of detrial kaolinite and quartz under Mesozoism. The finding of this study is an important for pyrophyllite ore prospecting in the Tongling region and the Middle-Lower Yangtze River Mineralization Belt which has similar ore-forming geological settings including the Wutong formation and Mesozoic magma.

Evalution of Water in Lunar Interior and Water Ice on Lunar Surface

WU Yanwei, HE Jiafeng, WANG Guoguang

2024, 30(02):  165-177.  DOI: 10.16108/j.issn1006-7493.2023013

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In the process of lunar exploration, water, as the source of life and an important propellant material for future interstellar travel, is one of the most concerned resources. Since United States Apollo and Soviet Union Lunar projects, the paradigm of “no water” on the Moon has been widely accepted for a long time. In this paper, the research progress on lunar interior water and surface water, the origin of lunar water, the evaluation of water resources, and the methods of exploitation and utilization are systematically reviewed. In recent years, the exploration of water resources on the lunar surface and the in-depth study of water content in lunar samples have revealed that the Moon may contain more water than that previously believed. Not only the interior of the Moon contains relatively abundant water, there are also considerable water resources in the polar region of the Moon. The origin of water on the Moon mainly includes original water that was not degassed during formation and differentiation of the Moon, water from asteroids and comets, and water from solar wind hydrogen implantation. It is estimated that the amount of water ice on the lunar surface is about 14.28 billion tons, and the amount of water caused by solar wind implantation on the lunar surface is about 340,000 tons, which will provide important resources for the construction of lunar bases and deep space exploration in the future. At present, a variety of development and utilization schemes have been proposed for the utilization of lunar water resources, including Thermal Mining of Water Ice on the Moon, Lunar Polar Propellant Mining Outpost (LPMO), The Combined System for Drilling and Extracting Lunar Water Ice and so on.

Geochronology, Geochemistry and Geological Significance of Amphibolites in Cenxi-Luchuan Area, Southeastern Guangxi

LIANG Renxin, SHI Yu, PANG Chaowei, LIU Xijun

2024, 30(02):  178-195.  DOI: 10.16108/j.issn1006-7493.2022093

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Zircon U-Pb geochronology and whole-rock geochemistry of amphibolites in Cenxi-Luchuan area, southeastern Guangxi are analyzed in this study. The results show that the amphibolites are probably formed later than the Early Palaeozoic (487-428 Ma). The Mid-Neoarchean zircons reveal that the unexposed Archean crystalline basement might be existed. The whole-rock geochemistry shows that the amphibolites are enriched in large ion lithophile elements (LILE) such as K, Rb, Ba, Sr, etc., and light rare earth elements relative to the original mantle. They are obviously depleted in high field strength elements (HFSE) such as Nb, Ta, Ti, etc., similar to the characteristics of island arc basalt (IAB). The amphibolites are formed by melting the mantle wedge of ancient subduction metasomatism, which might be in the lithospheric extension stage after collision in the Early Paleozoic.


Asteroid Microgravity Impact Sampling Study Based on Discrete Element Method Simulation

GENG Huan, ZHU Yao, LIU Chun, ZHANG Chenwei

2024, 30(02):  196-206.  DOI: 10.16108/j.issn1006-7493.2022094

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Impact sampling is a sampling method applicable to the microgravity environment on the surface of asteroids and has been successfully applied to the Hayabusa 1 and Hayabusa 2 asteroid exploration missions. In this paper, an asteroid microgravity
impact sampling model is developed based on the domestic high-performance discrete element software MatDEM. The effects of initial impact velocity and projectile shape on the interior regolith features and ejecta after impact are investigated. The results show that increasing initial impact velocity can increase the stress and dense degree inside the same region of the regolith, and increase the number of ejecta particles and the number of ejecta particles from the deep part of the regolith. Within the same area of the regolith, the cone-headed projectile produces the highest stress peaks and the flat-headed projectile produces the lowest stress peaks. Round and flat-headed projectiles produce the highest number of ejecta particles and have the best deep sampling capability. Cone-headed projectile produces the lowest number of ejecta particles and has the weakest deep sampling capability. The conclusions help to understand the internal mechanism of the impact process and provide a reference for the design of impact sampling schemes in deep space exploration.


Research of Full Dimension Monitoring Technology and Model Test of Slopes

CHENG Gang, Zhang Haoyu, ZHU Honghu, SHI Bin, WU Jinghong

2024, 30(02):  207-217.  DOI: 10.16108/j.issn1006-7493.2023005

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China is one of the countries with the most severe geological disasters, among which landslides are the most severe. Therefore, it is crucial to study landslide disasters deeply. Slope engineering is often affected by the superposition effect of human engineering activities and natural geological processes, which induce difficulty to scientific understanding of the slope deformation and instability mechanisms. To accurately grasp the slope state information, as well as the process of deformation and instability, a full-dimensional monitoring system is established to achieve dynamic interpretation and characterization of slope state information, thereby obtaining a more accurate, reliable, and intuitive basis for slope stability evaluation. In this paper, we comprehensively analyzes the‘air-space-ground-interior’integrated monitoring technology system of slopes from the perspectives of slope failure modes, typical slope monitoring technologies, and clarification of slope deformation evolution processes; Also, this study provides an overview and summary of the slope monitoring technology based on distributed fiber optic sensing (DFOS), with a focus on the research ideas and implementation paths of DFOS-based slope monitoring with multiple sources and fields. Further more, this study systematically reviews the process and results of physical model experiments of slopes based on typical monitoring technologies and DFOS technology, aiming to provide important reference for the design of slope reinforcement schemes and disaster prevention, mitigation and control.

Genetic Types and Origins of Upper Paleozoic-reservoiered Oil in Dongdaohaizi Sag and Its Surrounding Areas in the Junggar Basin

YIN Shengyu, GONG Deyu, SU Jing, HU Zhengzhou, WU Wei’an, WANG Ruiju

2024, 30(02):  218-230.  DOI: 10.16108/j.issn1006-7493.2022095

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Drilling in Dongdaohaizi sag started in the 1990s, but little progress has been made in oil and gas exploartaion due to the complex structural evolution and sedimentary characteristics for a long time. Recently, oil and gas indications have been  found repeatedly in the exploratory wells deployed in the Dongdaohaizi Sag, which has rekindled the hope of oil and gas exploration in this area. However, the understanding of the origin of oil and gas in this area is still poor, causing significant difficulties in selecting an exploration direction. Based on systematical analyses of stable carbon isotope composition, isoprenoid alkane, sterane terpane biomarkers, and other geochemical characteristics of crude oil and source rocks in the Carboniferous and Permian strata of Dongdaohaizi sag and its surrounding areas, the genetic types and oil sources were discussed. The results showed that the crude oil in the study area has entered the main oil generation window, which belongs to mature crude oil and can be divided into three different types. Type I oil is characterized by heavy stable carbon isotope composition, high Pr/Ph ratio, abundant C19 tricyclic terpanes, C20 tricyclic terpanes and C24 tetracyclic terpanes, and low gammacerane index. These features indicate that  it was derived from humic source rocks in the Lower Carboniferous Songkarsu formation, which was deposited in a freshwater environment. Type II oil is characterized by relatively light stable carbon isotope composition, relatively low Pr/Ph ratio, abundant β-Carotene, high gammacerane index, and low abundance of C19 tricyclic terpane, C20 tricyclic terpane, and C24 tetracyclic terpane. These features indicate that it was derived from the saline lacustrine source rocks in the middle Permian Pingdiquan formation. Geochemical characteristics of Type III oil are between those of Types I and II crude oil, showing a mixed source. The above findings provided a type case of oil source correlation in a multi-source superimposed area and also pointed out the direction for future petroleum exploration in the Dongdaohaizi sag and its surrounding areas.

Provenance and Tectonic Setting Analysis of the Wufeng-Longmaxi Formation Shale in the Sichuan Basin and Its Surrounding Area

PENG Hao, CHEN Lei, HU Yunpeng, LU Chang, HENG De, WEN Ran, TAN Xiucheng, QIN Hexing

2024, 30(02):  231-240.  DOI: 10.16108/j.issn1006-7493.2022097

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The Wufeng-Longmaxi Formation shales show great variations in sedimentological, mineralogical and geochemical characteristics across the Sichuan Basin and its surrounding areas. Provence and sources are the basis in determining  composition, mineralogy, and brittleness of shale. In this paper, we analyze the geochemical characteristics, source rock properties and tectonic setting of the Wufeng-Longmaxi shale in the Sichuan Basin and its surrounding areas based on major elements, trace elements, and rare earth elements data. The results show that the main components of the Wufeng-Longmaxi shale are SiO₂, CaO and Al₂O₃ in the Sichuan Basin and its surrounding areas. From the southwest to south -southeast -northeast Sichuan, the SiO₂ content in the Wufeng-Longmaxi Formation shale increases gradually, while the CaO content decreases gradually. The La/Yb-REE diagram shows that the source rocks of the Wufeng-Longmaxi Formation shale have certain variations in different areas of Sichuan Basin and its surrounding areas. The source rocks of the Wufeng-Longmaxi Formation shales are similar in southwest Sichuan and South Sichuan, mainly consisting of alkaline basalt, sedimentary rocks and granites. The shale source rocks of southeast Sichuan are mainly composed of granite and alkaline basalt, while the shale source rocks of northeast Sichuan are mainly composed of sedimentary rocks and granites. The ICV index analyses reveal that the source of the Wufeng-Longmaxi shales in southwest and south Sichuan is a result of rapid deposition of the first cycle of the near source, while the Wufeng-Longmaxi shales in southeast and northeast Sichuan have undergone recycling or strong chemical weathering. The analyses of Sc/Cr-La/Y diagram and other related parameters indicate that the Wufeng-Longmaxi Formation shale in the Sichuan Basin and its surrounding areas was deposited in a passive continental margin.