赣南茅坪钨矿床黄玉单晶流体包裹体研究

文章以赣南茅坪大型钨矿床成矿早阶段形成的黄玉单晶为研究对象,对其中的流体包裹体开展了岩相学、显微测温以及激光拉曼光谱研究。结果显示,茅坪钨矿床黄玉单晶中的流体包裹体以富液两相包裹体为主,同时发育有单相包裹体、富二氧化碳的三相包裹体以及含子矿物包裹体。其中,含子矿物包裹体发育是本矿床黄玉中包裹体的重要特征,子矿物成分有方解石、石英、石盐等;流体包裹体的均一温度介于200~509℃之间,峰值位于420~500℃之间,盐度w(NaCl_(eq))为4.32%~19.22%,峰值介于17%~19%,较前人获得的石英脉型钨矿床成矿温度和盐度均高出许多,其峰值(420~500℃)在一定程度上衔接了石英脉型黑钨矿高温阶段的演化历史;黄玉单晶中包裹体还具有富含CO_2、CH_4、N_2等挥发分的特征。综上所述,笔者认为石英脉型钨矿的成矿流体在早阶段具有高温、中高盐度、富挥发分、富含多种离子的特征。     

贵州碳酸盐岩风化壳中晶体石英形成条件分析:氧同位素证据

贵州碳酸盐岩风化壳中的晶体石英具有较强的测年潜力,其成因判别是年代学研究的前提和基础。对黔北、黔东地区3个碳酸盐岩风化壳剖面中的晶体石英和圆状石英进行了研究,拟通过晶体石英的δ18O值探讨其形成条件。结果表明,晶体石英的δ18O值在17.3‰～22.7‰范围内,平均为19.8‰,与火成岩、变质岩及热水(液)沉积中高温成因石英δ18O值明显不同;与砂岩中的碎屑石英、现代海滨砂中的石英以及风成沉积物中的石英等混合来源石英的δ18O值也有差异;尽管黔东大兴剖面中晶体石英和圆状石英的δ18O值相近,但它们的硅氧同位素相关关系不同,它们具有不同的成因;晶体石英的δ18O值分布在低温成因石英δ18O值范围内,这与其中未见两相包裹体的现象一致。结合实际资料和已有认识,推断晶体石英是包气带地表温度(15～25℃)条件下缓慢生长形成的;其形成过程与碳酸盐岩风化成土的两阶段模式密切相关:酸不溶物风化形成的含硅流体向下淋滤至风化壳底部后被圈闭在已形成的孔隙、空洞中,由于蒸发作用达到过饱和而缓慢结晶形成晶体石英。     

Petrogenesis of the Piqiang mafic-ultramafic layered intrusion and associated Fe-Ti-V oxide deposit in Tarim Large Igneous Province,NW China

ABSTRACT

The Piqiang intrusion is one of the two important ma?c-ultrama?c layered intrusions that host giant Fe-Ti-V oxide deposits in the Permian Tarim Large Igneous Province, NW China. The intrusion mainly consists of gabbro, anorthosite and minor plagioclase-bearing clinopyroxenite in the marginal zone. Disseminated to massive Fe-Ti oxide ores occur as layers and lenses within the gabbro. SHRIMP zircon U-Pb results from both a gabbro from the Piqiang intrusion and a granite from the surrounding granitic dyke yield ages of ~270 Ma. Geochemically, the Piqiang silicate rocks are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high ?eld strength elements (HFSE), and have a limited range of Sr-Nd-Hf isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the layered units suggest that all the rocks are co-magmatic. The parental magma is Fe-Ti-rich and is akin to the most primitive diabasic dyke which is associated with the Piqiang intrusion. Partial melting of the Tarim mantle plume with involvement of a subduction-metasomatized lithospheric mantle source best explains the geochemistry and petrogenesis of the parental magmas of the Piqiang intrusion. We propose that the lithospheric mantle source may have been metasomatized by subduction-related materials and the metasomatic enrichment of this source region which may be correlated with oceanic sediment recycling during southward subduction of the South Tianshan oceanic slab during the Early-Middle Paleozoic. Crystal settling and mechanical sorting is the predominant process responsible for the formation of the massive Fe-Ti oxide ores in the Piqiang intrusion. Central to ore formation is a combination of the protracted differentiation history of a Fe-Ti-enriched parental magma and the later addition of external H₂O from the country rocks to the slowly cooling magma chamber.     

矿物晶体形态统计方法探讨

矿物晶体形态标型研究广泛应用于矿床成因研究和成矿预测工作,是成因矿物学研究中一个很重要的方面。文章以黄铁矿晶体形态统计为例,介绍了适用于简单晶体形态统计的形态统计法、适用于复杂晶体形态统计的习性统计法,以及根据实际观测实践提出的权重统计法。通过对这3种方法的比较,指出了不同方法的利弊,给出了根据不同研究目的及样品实际情况选择不同方法的建议。     

鄂尔多斯盆地镇泾区块上三叠统延长组砂岩中绿泥石矿物特征

本文对鄂尔多斯盆地镇泾区块上三叠统延长组长8油层组砂岩中绿泥石矿物的类型、赋存状态、形成时间、晶体化学特征及成因机制进行了较为系统的研究.结果表明研究区的绿泥石以铁镁绿泥石和铁斜绿泥石为主,包括陆源碎屑绿泥石、自生绿泥石和蚀变绿泥石3种,自生绿泥石又包括颗粒包膜、孔隙衬里和孔隙充填绿泥石3种,以孔隙衬里绿泥石为主,形成...     

黄铁矿中不同赋存状态金的测试及意义 —以胶莱盆地金矿中黄铁矿为例

本文论述了黄铁矿中晶格金、自然金、石英包体金的分离技术及测试方法,它可用于研究金矿载金矿物黄铁矿中不同赋存状态金与成矿的关系。运用本方法对胶莱盆地典型金矿中主成矿阶段黄铁矿三种赋存状态的金进行了测试,发现以自然金为主,且自然金含量比例差别不大,说明盆地中的金矿可能具有相同成矿流体和环境。通过对含矿与不含矿黄铁矿中离子晶格金含量研究,进行了靶区预测验证。研究发现黄铁矿中存在石英包体金,且部分金矿中石英包体金含量较高,普通测试方法可能丢失该类金,造成样品分析结果偏低,进而出现丢矿或资源量估算不准确的现象。     

新疆大黑山东部姜巴斯套组下段的凝灰岩锆石LA-ICP-MS U-Pb年龄及其地质意义

准噶尔东部大黑山地区出露的姜巴斯套组为一套厚层海相火山-沉积地层,其形成时代及地层层序存在争议.对姜巴斯套组下段2个具有地层意义的晶屑凝灰岩开展的锆石LA-ICP-MS测年,获得的加权平均年龄分别为339.4±1.9 Ma(MSWD = 0.39)和336.3±2.6 Ma(MSWD=0.58),结合古生物新的研究成果...     

辽宁瓦房店金伯利岩中石榴石特征及种类鉴定

辽宁瓦房店金刚石矿区金伯利岩中的石榴石一直被当作镁铝榴石。为了确定矿区颜色复杂的石榴石种类,本文对矿区的石榴石进行了系统的采样分析,测定了112件石榴石样品的晶胞参数、50件样品的微区化学成分和40件样品的红外光谱。利用石榴石晶胞参数、红外光谱、化学成分和化学分子式方法对矿区石榴石进行分类,结果显示:晶胞参数分类法误差大,容易得出错误结论;红外图谱分类法准确度不高,只能作为参考方法;化学成分分类法太过笼统,达不到详细划分石榴石种类的目的;化学分子式分类法可把矿区的石榴石详细划分6个矿种:镁钙铁-铝铬铁榴石、镁铁钙-铝铬铁榴石、镁钙铁-铝铬榴石、镁钙-铝铬铁镁榴石、镁铁钙-铝铬榴石、镁铁钙-铝铁铬榴石,每种石榴石都充分反映了A、B离子的种类及占位特征,是4种分类方法中最为科学的方法。研究认为瓦房店金刚石矿区金伯利岩中石榴石A端元成分以Mg²⁺离子占位为主;B端元成分以Al³⁺离子占位为主。由于阳离子替代普遍,A、B端元成分复杂,瓦房店金伯利岩中不存在单纯意义上的镁铝榴石。     

Apatite recrystallisation during prograde metamorphism,Cooma, southeast Australia: implications for using an apatite – graphite association as a biotracer in ancient metasedimentary rocks

The major patterns in the evolution of life during the Phanerozoic are reviewed. Critical transitions in the evolution of life that reflect increases in ecological complexity are the Cambrian radiation; the Ordovician biodiversification and its subsequent diversification and transition into the Modern Marine Fauna following the Permo-Triassic mass extinction; the colonisation of land, and its subsequent diversification; and the biological colonisation of the atmosphere. This increase in ecological diversity and complexity was often accompanied by increases in morphological complexity, arising, in part, from elaboration of the developmental program. However, it was additionally fuelled by increases in diversification and disparity arising also from morphological simplification in some lineages as developmental program became reduced.     

Constraints on Cation Order in Calcium-rich Sedimentary Dolomite

Most sedimentary Ca-rich dolomite in pre-Holocenerocks is known to exhibit a fine-scale modulation inTEM images, reflecting a domain structure of which onecomponent is a low-symmetry variant of dolomite. Thevarious structural models proposed for thelow-symmetry component involve Ca–Mg order patternsthat are different from that in dolomite. Caution istherefore required for interpretation of X-raydiffraction data, which average over the entirestructure. The average structures of two Ca-richdolomites having a structural modulation are refinedusing single-crystal intensity data. The resultsindicate a poor fit using a dolomite model, which isconsistent with the findings from TEM and electrondiffraction indicating that one component of thedomain structure is different than dolomite. Resultsalso indicate that average model A and B cation siteshave mixed Ca–Mg occupancy, which provides someconstraints on possible models for the low-symmetrydomains.