湖南浏阳永和碳酸盐岩中的天青石

湖南浏阳永和天青石赋存于二叠系栖霞组,由生物屑泥灰岩或泥晶灰岩构成的灰岩瘤状体中。瘤状体中含一团或数团呈放射状类似菊花的天青石晶簇。 分析结果证实,本区天青石晶体成分纯净,仅含有少量方解石。据化学分析数据,运用氧原子法计算,其晶体化学式是（Sr 0.97600,Ba 0.0012）SO₄。 野外和镜下观察以及碳、氧同位素分析表明,菊花状天青石是在碳酸盐沉淀后,在成岩阶段,由于介质性质（Eh、pH等）的变化,原先呈分散状分布的天青石重新溶解,向弱酸性和氧逸度较高的地方聚集结晶而成。     

沉积型天青石矿床的地质特征及其成因探讨

沉积型天青石矿床和蒸发岩类 ,特别是石膏的沉积密切相关 ,含矿地层主要是纹层状叠层石或藻灰岩。天青石中硫、锶同位素值和海水硫、锶同位素值相近。在蒸发条件下海水浓缩到一定浓度时 ,产生天青石沉积 ,或是富锶的硫酸型晶间卤水和钙碳酸盐反应 ,形成交代型天青石。天青石主要分布于蒸发盐盆地的边缘部位 ,位于钙碳酸盐和钙硫酸盐沉积的过渡带     

米粒状白云石及其出溶成因

米粒状白云石产于奥陶系近岸碳酸盐岩序列的云斑(生屑)泥晶灰岩、砾屑灰岩和叠层石灰岩中,在虫孔和砾屑粒间最为富集,外形为伸长菱面体,薄片中呈米粒状.晶体无环带或雾心,但内部含大量呈规则分布的细小方解石“包体”,结晶C轴垂直于晶体延长方向.与背景方解石泥晶相比,Fe、Mn、Na和Ba含量较高,Sr含量较低.C轴的固定取向排除了石膏假晶的可能,也不是普通白云石化或交代钡白云石的结果,推测是沉淀镁方解石重结晶后在压力增加的条件下经出溶作用形成.     

黄龙铺钡天青石的矿物学研究及其意义

黄龙铺钼矿床中脉石矿物“天青石”以其颜色、粗大晶体和形态引人瞩目。该矿床的辉钼矿—方铅矿—黄铁矿—“天青石”—石英—方解石脉,呈大脉和网脉状产于熊耳群细碧岩内。“天青石”除在黄龙铺产出外,在邻近地区构成矿床(点),因此,确定其确切种属不仅有矿物学意义,而且对其矿床(点)进行合理评价也有实际价值。我们根据该矿物的物理性质和化学成分并与国外钡天青石资料对比,将其定名为钡天青石。     

川东地区锶矿床地质特征及成因探讨

川东是我国锶矿资源远景最大，质量最佳的成矿区。铝矿产于下三叠统嘉陵江组二、四段的灰岩－白云岩－天青石膏质藻层纹白云岩－石膏岩（或灰岩）韵律层中。天青石膏质藻层纹白云岩是含矿层。准同生阶段已有天青石沉积，局部富集形成矿源层。在后生阶段的热力、压力驱动下．四川盆地的热卤水（２２０～３００℃）沿含矿层交代形成条纹条带状天青石矿层；第二期热卤水（１５０～２２０℃）在含矿层及其附近的碳酸盐岩裂隙中充填交代，形成四块状、脉状天青石；第三期热卤水（＜１５０℃）沿断裂充填形成天青石、重晶石脉。一、二期热卤水成矿作用常相互叠加，形成工业矿床。川东褶皱带西部背料部位具良好的找矿前景。     

安徽灵璧地区新元古代臼齿构造（徽亮晶）碳酸盐沉积及意义

微亮晶碳酸盐岩是一种发育在前寒武纪尤其是元古代的特殊类型碳酸盐岩,它在结构上与基质有明显区别,是由均一、等轴、多边形的微亮晶方解石组成,个体为5～15μm。安徽灵璧地区微亮晶碳酸盐岩按其成因可分为原地和异地两类。原地微亮晶主要分布于泥晶灰岩、粉屑泥晶灰岩、泥灰岩或泥岩中;异地微亮晶主要发育在粉屑灰岩或砾屑灰岩中。微亮晶碳酸盐岩的岩石学特征指示其形成并发育于稳定克拉通浅海潮下及环潮坪环境,特别是中浅缓坡向上变浅旋回的底部,风暴浪基面是其发育的最大深度。微亮晶碳酸盐岩作为一种具有全球性意义的沉积碳酸盐岩类,具有特定的时限分布范围,这对于提高前寒武纪地层对比精度具有重要意义。     

黄龙铺钡天青石的矿物学研究及其意义

黄龙铺钼矿床中脉石矿物“天青石”以其颜色,粗大晶体和形态引人瞩目。该矿床的辉钼矿—方铅矿—黄铁矿—“天青石”—石英—方解石脉,呈大脉和网脉状产于熊耳群细碧岩内。“天青石”除在黄龙铺产出外,在邻近地区构成矿床(点),因此,确定其确切种属不仅有矿物学意义,而且对其矿床(点)进行合理评价也有实际价值。我们根据     

青海大风山天青石矿床地质特征及成因分析

大风山天青石矿床位于柴达木盆地西北部,由Ⅰ、Ⅱ、Ⅲ、Ⅳ四个矿区组成,赋矿地层为第三系上新统狮子沟组,含矿层位不稳定,矿体多呈薄层状、扁豆状或透镜状产于含碳钙质泥岩中,矿石主要为天青石、菱Sr矿等;矿区内东西、北东东向次级断裂及舒缓短轴复式背斜构造严格控制着天青石矿体的产出形态;成矿物源具有多源性,一方面周边山系含Sr水为主要补给源,其次为富Sr的油田水。另外,深部含Sr卤水的补给也具有重要作用;矿床成因具有陆相湖泊化学沉积-热水沉积叠加改造型矿床特征。     

新疆乌恰县帕恰布拉克天青石矿床成因研究

应用岩相学及矿相学镜下鉴定、粉晶衍射半定量分析、包裹体测试分析及电子探针分析技术,结合地质温压计估算流体的温度,对天青石矿床的成因进行探讨。结果表明,新疆乌恰县帕恰布拉克天青石矿床中矿石类型主要有厚层块状天青石岩、天青石化灰岩、天青石化硅质细砾岩及热液角砾状天青石岩。矿物主要为天青石、方解石、白云石等。成矿流体主要为3种类型,分别为气相高温中盐度流体、液相中温高盐度流体及液相低温低盐度流体。矿床的形成可划分为2个期次5个阶段,其中2个期次分别为热卤水同生沉积成岩成矿期、盆地流体改造期。5个阶段为富锶热卤水同生沉积-交代阶段、富锶热卤水同生沉积阶段、热卤水喷流沉积阶段,后期含碳酸盐质的热水混合沉积阶段,盆地流体改造阶段。     

青海尖顶山锶矿床地质特征及成因分析

尖顶山天青石矿床位于柴达木盆地西北缘,矿体主要产于上新统狮子沟组上段含碳钙质泥岩及灰岩中,呈层状、似层状、透镜状,矿石以原生天青石矿石为主,品位较高,连续性好。含矿砂岩ΣREE值较低,平均为42.73×10~(-6),LREE/HREE平均为6.48;δEu平均为0.94,δCe平均为0.98;La/Yb-REE图中含矿岩石投点于沉积岩区,显示成矿物源具有多来源性特征;天青石矿的形成可能与深层地下卤水及盆地周缘陆缘碎屑物质富矿流体的补给紧密相关,表明该矿床成因可能具有陆源碎屑化学沉积型特征。     

浏阳式菊花石的特征及其地质找矿意义

菊花石是天青石矿物在岩石中呈三度空间发育的放射状集合体。白色或微带黄色色调,半透明,因状如菊花故得名。湖南浏阳是盛产此珍贵石雕工艺品原料之地,故名浏阳式菊花石浏阳菊花石已有一百多年的开采历史,在1915年巴拿马国际博览会上荣获金奖。但在矿物学上的进一步认识,以及在地质学上把它作为一种找矿标志来加以重视,却是近几年的事。它赋存于华南二叠纪碳酸盐岩中,与世界上稀缺的海泡石粘土同属一个层位,密切共生,因而成为华南寻找海泡石的一个重要宏观标志。其分布如图1所示。     

论华南栖霞组中的菊花石

本文中的菊花石指华南栖霞组中由柱状晶体放射状排列而成的菊花状晶簇。它最早发现于湖南浏阳永和镇栖霞组上部(方邺森等人,1988),之后又见于广西来宾县城郊栖霞组上部(沙庆安等人,1990),它们被认为是天青石或天青石假象。笔者(1991)在湖北省黄石地区栖霞组上部发现该类假象,并认为其原生矿物是六水碳钙石。虽然它们分别被解释成不同矿物,但无论是外部形态还是内部成分、结构构造均具极大的相似性。对该矿物集合体的不同解释将对栖霞组沉积环境的认识产生重要影响。本文通过与六水碳钙石假象的对比,讨论该矿物集合体的成因及其环境意义。不妥之处请批评指正。     

Nodular celestite in the Chihsia Formation (Middle Permian) of south China

The middle Permian Chihsia Formation of south China accumulated on a shallow shelf, and consists mainly of black to dark grey micritic limestone rich in chert nodules and organic matter. A unique type of nodular crystal cluster is distributed widely in the carbonate succession. Most crystal clusters consist of calcite. Some, however, are composed of celestite, and geochemical, microscopic and crystal morphological data suggest that celestite was the precursor of the calcite. The celestite developed displacively within the sediments during early diagenesis, before compaction and before local dolomitization of the host rock. Similar strontium isotopic values were obtained from the celestite clusters, replacement calcite, vein calcite and host rock. The values are within the range of middle Permian sea water. The strontium in the celestite was furnished chiefly by either diagenetic alteration of strontium‐rich marine aragonite to strontium‐poor calcite, or aragonite dissolution induced by aerobic oxidation of organic matter, or both. The sulphur isotopic values of the celestite are about 6–11‰ heavier than the sulphur isotopic value of sulphate in coeval sea water. Based on geological context, this difference is attributed to microbial reduction of porewater sulphate in the Chihsia sediments.     

菊花石中纳米矿物的微观组织研究

采用扫描电镜、透射电镜和能谱分析研究了浏阳产菊花石的微观组织,发现浏阳菊花石的花瓣保留了原生矿物——天青石SrSO₄及其单晶体的外形,但是花瓣内部出现了硅化现象;菊花石中存在多种纳米矿物材料,例如非晶纳米硅氧线、颗粒状纳米CaCO₃和SrSO₄、CaCO₃的二维纳米片和纳米带等。某些非晶纳米硅氧线外包覆了纳米晶化层,镁含量越高,非晶纳米线越容易晶化。     

菊花石及其他两种放射状形貌对比研究

通过天青石菊花石形貌与红柱石菊花石钟乳石截面放射状形貌的对比,找出它们形成的共同规律,并从形貌细节差异上分析了其形成机制和条件的差别。     

华南二叠系栖霞组菊花状天青石锶同位素特征及其地质意义

菊花状天青石是华南地区栖霞组内一种特殊的矿物集合体,形成于早期成岩作用阶段。在研究其成因过程中,系统分析了湖北黄石和湖南浏阳栖霞组内菊花状天青石的Sr同位素组成以及湖南浏阳、湖北黄石、江西永丰和广西来宾四处天青石假象、天青石围岩（泥晶灰岩）和围岩中方解石脉的Sr同位素组成。Sr同位素分析结果表明,天青石中的87Sr/ 86Sr最高值为0.707525,最低值为0.706981,平均值为0.707215。与天青石相比,天青石假象、天青石围岩和方解石脉的87Sr/ 86Sr值整体相对富含87Sr。由于天青石假象和方解石脉明显为晚期成岩作用成因,它们相对富含87Sr的锶同位素特征应是晚期成岩作用叠加的结果,与其类似的泥晶灰岩的87Sr/ 86Sr值也可能同样受到了晚期成岩作用的影响。栖霞组菊花状天青石比同组泥晶灰岩更好地记录了栖霞期海水的Sr同位素组成。     

Mineralogical and isotopic record of biotic and abiotic diagenesis of the Callovian-Oxfordian clayey formation of Bure (France)

The Callovian-Oxfordian (COx) clayey unit is being studied in the Eastern part of the Paris Basin at depths between 400 and 500 m depth to assess of its suitability for nuclear waste disposal. The present study combines new mineralogical and isotopic data to describe the sedimentary history of the COx unit. Petrologic study provided evidence of the following diagenetic mineral sequence: (1) framboidal pyrite and micritic calcite, (2) iron-rich euhedral carbonates (ankerite, sideroplesite) and glauconite (3) limpid calcite and dolomite and celestite infilling residual porosity in bioclasts and cracks, (4) chalcedony, (5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ³⁴S (−38‰ to +34.5‰), providing evidence of bacterial sulphate reduction processes in changing sedimentation conditions. The most negative values (−38‰ to −22‰), measured in the lower part of the COx unit indicate precipitation of pyrite in a marine environment with a continuous sulphate supply. The most positive pyrite δ³⁴S values (−14‰ up to +34.5‰) in the upper part of the COx unit indicate pyrite precipitation in a closed system. Celestite δ³⁴S values reflect the last evolutionary stage of the system when bacterial activity ended; however its deposition cannot be possible without sulphate supply due to carbonate bioclast dissolution. The ⁸⁷Sr/⁸⁶Sr ratio of celestite (0.706872-0.707040) is consistent with deposition from Jurassic marine-derived waters. Carbon and oxygen isotopic compositions of bulk calcite and dolomite are consistent with marine carbonates. Siderite, only present in the maximum clay zone, has chemical composition and δ¹⁸O consistent with a marine environment. Its δ¹³C is however lower than those of marine carbonates, suggesting a contribution of ¹³C-depleted carbon from degradation of organic matter. δ¹⁸O values of diagenetic chalcedony range between +27‰ and +31‰, suggesting precipitation from marine-derived pore waters. Late calcite crosscutting a vein filled with chalcedony and celestite, and late euhedral quartz in a limestone from the top of the formation have lower δ¹⁸O values (∼+19‰), suggesting that they precipitated from meteoric fluids, isotopically close to present-day pore waters of the formation. Finally, the study illustrates the transition from very active, biotic diagenesis to abiotic diagenesis. This transition appears to be driven by compaction of the sediment, which inhibited movement of bacterial cells by reduction of porosity and pore sizes, rather than a lack of inorganic carbon or sulphates.     

华蓥山地区天青石矿稀土元素地球化学特征

华蓥山地区天青石矿各类型天青石的稀土总量(∑REE)均较低,为轻稀土富集型。巨晶天青石和条带状矿石之白色条带状天青石具铕的正异常,为热卤水成因,层状和条带状矿石之暗色条带天青石具δ Eu的负异常,与碳酸盐岩围岩一致,为沉积成因。区内天青石、碳酸盐岩表现为δ Ce的轻度负异常或无异常,与该区早三叠世嘉陵江组沉积时期所处的含膏泻湖相沉积环境有关。     

Geochemistry of Sedimentation and Diagenesis in Qixia Formation (Early Permian) of Badong,Hubei Province, China: Implications for T-R Cycle Interpretation

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