我国电气石矿产资源开发前景分析

电气石是近年来开发的重要的新型功能矿物材料。文章论述了我国电气石矿产的类型、成矿特点及电气石矿产产出时空分布特征,表明我国具有电气石矿产资源优势。同时介绍了电气石矿物功能特性和电气石应用产品,展现我国电气石资源开发应用前景。     

江苏地矿实验室生存发展新思路

1949年以来,江苏地矿实验室为江苏地矿事业的发展做出很大贡献。跟随国家机构改革的步伐,地矿实验室实现了属地化改造,隶属于国土资源系统。由于上级主管部门的缺失,江苏地矿实验室的生存与发展面临困境,本着立足江苏为出发点,提出了几点发展新思路。     

Evolution of the composition of seawater through geologic time, and its influence on the evolution of life

The redox state of the surface environment of the early Earth is still controversial, and a detailed and quantitative estimate is still lacking. We carried out in-situ analyses of major, trace, and rare-earth elements of carbonate minerals in rocks with primary sedimentary structures in shallow and deep sea-deposits, in order to eliminate secondary carbonate and contamination of detrital materials, and to estimate the redox condition of seawater through time. Based on the Ce content and anomalies of the carbonate minerals at given parameters of atmospheric CO₂ content (pCO₂) and Ca content of seawater, we calculated the oxygen contents of shallow and deep seawater, respectively. The results show that the oxygen content of the deep sea was low and constant until at least 1.9 Ga. The oxygen content of shallow seawater increased after 2.7 Ga, but fluctuated. It became quite high at 2.5 and 2.3 Ga, but eventually increased after the Phanerozoic. In addition, the calculation of a high pCO₂ condition shows that seawater was more oxic even in the Archean than at present, suggesting a relatively low pCO₂ through geologic time.Our detailed calculations from compositions of carbonate minerals in Three Gorge area, south China show a low oxygen content of seawater after the Snowball Earth until the late Ediacaran, an increase in the late Ediacaran, and a significant decrease around the Precambrian–Cambrian and Nemakit/Daldynian–Tommotian boundaries. These variations were possibly caused by global regression and dissolution of methane hydrates.     

Provenance of Cretaceous clastics in the Subhercynian Basin: constraints to exhumation of the Harz Mountains and timing of inversion tectonics in Central Europe

The Harz Mountains and the adjacent Subhercynian Cretaceous Basin figure as the most prominent surface representative for Late Cretaceous inversion structures in Central Europe. Facies, depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the Harz. From Hauterivian to Early Santonian there is no evidence for detrital input from the nearby Harz area. Sediments are mature quartzarenites derived from Paleozoic basement rocks and/or recycled Permian to Mesozoic sedimentary rocks. This situation changed drastically in Middle to Late Santonian when freshly exhumed and eroded Mesozoic sedimentary cover rocks of the Harz were delivered into the basin. Feldspar and lithoclasts reflect erosion of Triassic and, in places, Jurassic to Turonian strata. Apatite and garnet in heavy mineral spectra are derived from largely unweathered Lower Triassic Buntsandstein as indicated by apatite and garnet chemistry. In Early Campanian, Paleozoic lithoclasts indicate erosion cutting down into the basement of the Harz. Simultaneous strong decrease of feldspar, garnet and apatite suggest an almost complete removal of the 2–3 km thick Mesozoic cover of the Harz within only 2–4 Myr. This translates into an exhumation rate of approximately 1 mm/a consistent with apatite fission track data from granitoid rocks of the Harz Mountains.     

南极普里兹湾主要碎屑矿物特征及物源分析

基于南极普里兹湾海域33个表层碎屑沉积物样品的碎屑矿物学分析,对该区的沉积环境与物质来源进行了分析。结果表明该区碎屑重矿物共17种,石榴子石、普通角闪石和磁铁矿为优势矿物,紫苏辉石和赤铁矿为特征矿物。根据矿物组合分布特征,普里兹湾可划分为4个矿物区:Ⅰ区为石榴子石含量占绝对优势、重矿物含量较高的弗拉姆浅滩矿物区;Ⅱ区为石榴子石、普通角闪石含量较高,磁铁矿为特征矿物的普里兹水道矿物区;Ⅲ区为紫苏辉石含量较突出的四女士浅滩矿物区;Ⅳ区为普通角闪石含量明显突出,石榴子石显著减少的深水陆坡矿物区。通过电子探针测试研究区石榴子石结果表明:碎屑石榴子石含有较高的Fe、Mg和较低的Ca、Mn,属主要来源于高级麻粒岩相副变质岩的A型石榴子石。普里兹湾海域的碎屑矿物分布特征是物质来源、海流系统以及冰川活动等多重因素综合作用的产物。     

Dissolution kinetics of selected natural minerals relevant to potential CO2-injection sites − Part 1: A review

This publication provides a literature review on experimental studies of dissolution kinetics of mainly carbonates and feldspar group minerals, i.e. most common minerals at potential CO₂-injection and/or storage sites. Geochemical interaction processes between injected CO₂ and coexisting phases, namely reservoir and cap rock minerals and formation fluids close to the CO₂-injection site can be simulated by flow-through or mixed flow reactors, while processes far from the injection site and long-term processes after termination actual CO₂-injection can be mimicked by batch reactors. At sufficient small stirring rates or fluid flow rates as well as low solute concentrations flow-through reactors are also able to simulate processes far from the injection site. The experimental parameter temperature not only intensifies the dissolution process, the dominant dissolution mechanisms are also influenced by temperature. The dissolution mechanisms change from incongruent and surface controlled mechanisms at lower temperatures to congruent and transport controlled mechanisms at higher temperatures. The CO₂ partial pressure has only a second order influence on dissolution behavior compared to the influence of pH-value and ionic strength of the CO₂-bearing brine. Minerals exposed to CO₂-bearing brines at elevated temperatures and pressures are subject of alteration, leading to severe changes of reactive surfaces and potential precipitation of secondary minerals.Computational simulations of mineral reactions at potential CO₂ storage sites have therefore to include not only the time-resolved changes of dissolution behavior and hence kinetics of mineral dissolution, but also the influence of secondary minerals on the interaction of the minerals with CO₂-enriched brines.     

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite,Yarlung Zangbo Suture Zone,Western Tibet,China: Implication for its Origin

The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements (PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios (<0.1). In mid-ocean ridge basalts (MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral (PGM) grains were discovered from the samples, including laurite, erlichmanite, Os-Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os-Fe alloy and increased thereafter, with the fall in temperature. Primary Fe-Ni and Fe-Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high-pressure and low-pressure chromites. Low-pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high-pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.     

地表“矿物膜”半导体矿物光电子调控微生物群落结构演化特性研究

矿物-微生物交互作用广泛参与地球表层系统物质循环与能量流动过程,深刻地影响着一系列重要的地表生物地球化学进程。近年来地表半导体矿物的相关研究,为矿物-微生物交互作用提供了崭新研究方向,揭示地表“日光-半导体矿物-微生物”系统电子传递过程及其环境效应,是地质微生物学交叉领域研究的核心科学问题之一。本研究从地表不同生境“矿物膜”出发,以光电化学技术证实喀斯特、红壤、岩石漆“矿物膜”在1 000 min长时间循环实验中平均光电流值约为5.4、3.4、3.2 μA/cm²,证实“矿物膜”良好日光响应特性且铁锰氧化物矿物在其中发挥核心作用。基于笔者前期研究所发现的“矿物膜”电活性菌富集且与半导体矿物分布呈正相关性这一现象,本文进一步构建模拟光电子红壤细菌群落系统,20天后细菌群落α多样性显著提升,研究证实细菌群落具有模拟光电子响应活性,且电极与溶液群落均具有演化方向性;16S rRNA测序分析表明模拟光电子作用下Shewanella、Pseudomonas、Streptococcus、Lactobacillus、Acinetobacter等电活性菌显著富集。综上,本文研究结果间接证实地表半导体矿物光电子可有效调控微生物群落结构并促进电活性菌在“矿物膜”中富集。     

矿物热电效应与火山地震之热电异常

地壳物质组成的不均一性及矿物形成物理化学条件的复杂性决定了地壳内广泛存在半导体矿物。半导体矿物的主要特征之一是晶格内存在一定量由成分(本征元素或杂质元素)异化或结构缺陷形成的潜在载流子。当遇有温差热激发条件时,梯度温度场会驱动矿物晶体内的潜在载流子定向移动,进而产生温差热电势,这种现象称作热电效应。一般来说,火山地震孕育和发生过程中其震源处常常存在由扰动热流而产生的不均匀热场,该热场的梯度效应(温差效应)能够触发半导体矿物产生热电效应,并将热能转化成电能。因此推测,作为火山地震的重要前兆之一,地电异常的出现很可能存在热电效应的贡献,即火山地震地电异常存在热电效应机制。这一认识对于深刻理解火山地震孕育过程中的地电异常具有启示意义。     

南极半岛西北部海域表层沉积物碎屑矿物研究

本文通过对南极半岛西北部海域23个表层沉积物中碎屑矿物分析研究,获得以下结果:1.主要矿物有单斜辉石、斜方辉石、角闪石、绿帘石、磁铁矿、钛铁矿、黄铁矿、白云母、黑云母、绿泥石、橄榄石,玄武闪石、石榴石、磷灰石、锆石、金红石及火山玻璃、斜长石、石英等;2.根据矿物分布特征和稀土元素特征本区可分为三个矿物区和三种矿物组合类型:①基性火山碎屑矿物沉积区,矿物组合类型为辉石-火山玻屑型;②中酸性火成矿物沉积区,矿物组合类型为辉石-绿帘石-角闪石-石英;③基性火山碎屑矿物和变质矿物混合沉积区。矿物组合类型为辉石-绿帘石-石榴石-石英-火山玻屑。