山东含矿金伯利岩的氧、硅同位素地球化学研究

山东胜利1号和红旗6号金伯利岩管是我国著名的原生金刚石矿床。文章以该岩管的各类金伯利岩、深源捕虏体及围岩为测定对象,研究了金伯利岩管的O、Si同位素组成。结果表明,O、Si同位素对揭示含矿金伯利岩形成的地质背景,重塑含矿金伯利岩管的岩相,具有较显著的示踪作用。     

金伯利质岩管的认识及其找矿意义

金伯利岩是世界上分布较少和较难寻找的岩石。因其含有金刚石, 具经济价值,含有地幔捕虏体,给科学界带来地壳深部和上地幔信息,一直为地学界所关注。金伯利岩多呈管状产出,岩管中含有来自上地幔的同源包体以及上升通道周边各种岩石的捕虏体,火山爆发所形成的火山碎屑的复杂性造成其岩石命名有多种不同的认识,有关术语及其用法非常多。在研究国内外关于金伯利岩成果的基础之上,本文将术语用法和岩石命名原则进行分析和总结,解剖三种类型金伯利质岩管在纵向上的变化,分析在中国所发现的含金刚石的金伯利质岩管的特征和分析可能存在的金刚石砂矿。     

华北克拉通金伯利岩型金刚石矿床含矿性判别

金伯利岩型金刚石原生矿床含矿性评价是了解金刚石成矿规律和指导区域性找矿的重要依据。华北克拉通是我国重要的金刚石成矿远景区,目前已发现了两个重要的含金刚石金伯利岩岩区（山东蒙阴和辽宁瓦房店）。近年来,对岩区内不同品位金刚石典型矿床的研究表明金伯利岩中的金刚石品位取决于以下两个重要的地质过程：金伯利岩岩浆对金刚石的捕获作用和金伯利岩岩浆对金刚石的熔蚀作用。在华北克拉通下方存在一个金刚石稳定区,温度为950~1200 ℃,压力为4. 4~6. 1 GPa。山东蒙阴和辽宁瓦房店金伯利岩岩浆在上升过程中穿过该区域并捕获其中的金刚石,成为含矿岩浆;而铁岭和鹤县等金伯利岩岩浆在上升过程中不穿过该区域,成为不含矿岩浆。在穿过金刚石稳定区时,富矿的金伯利岩捕获了更多的金刚石以及金刚石的伴生指示矿物（如镁铝榴石,镁铬铁矿）;而贫矿的金伯利岩则相对捕获了少量的金刚石和指示矿物。这些指示矿物往往参加了金刚石的形成过程,有些作为缓冲剂控制了反应（岩浆或熔体）的氧化还原状态,有些则作为反应物或者生成物参与到反应中。部分指示矿物（如镁铝榴石）还进一步地记录了金刚石形成后金伯利岩岩浆对金刚石的交代作用。金伯利岩岩浆温度（T）,氧逸度（fO2）和挥发份(H2O和CO2)均会对金刚石的熔蚀作用产生影响,其中氧逸度作用最大,温度次之,而挥发份作用最弱。在华北克拉通,金伯利岩中指示矿物（镁铝榴石、镁铬铁矿）和金伯利岩岩浆特征（温度,氧逸度和挥发份）共同组成了金伯利岩型金刚石原生矿的评价指标。     

博茨瓦纳和中国含金刚石金伯利岩的地质特征及对寻找类似岩体的启示

金刚石及其寄主岩石是人类认识地球深部物质组成和性质、壳幔和核幔物质循环重要研究对象。本文总结了中国不同金刚石类型的分布,着重对比了博茨瓦纳和中国含金刚石金伯利岩的地质特征,取得如下认识:(1)博茨瓦纳含矿原生岩石仅为金伯利岩,而中国含矿岩石成分复杂,金伯利岩主要出露在华北克拉通,展布于郯庐、华北中央和华北北缘金伯利岩带,具有工业价值的蒙阴和瓦房店矿床分布于郯庐金伯利岩带中;钾镁煌斑岩主要出露在华南克拉通,重点分布在江南和华南北缘钾镁煌斑岩带中;(2)钙钛矿原位U-Pb年龄和Sr、Nd同位素显示,86～97 Ma奥拉帕金伯利岩群和456～470 Ma蒙阴和瓦房店金伯利岩均具有低87Sr/86Sr(0.703～0.705)和中等εNd(t)(-0.09～+5)特征,指示金伯利岩浆源自弱亏损地幔或初始地幔源区;(3)博茨瓦纳金伯利岩体绝大多数以岩筒产出,而中国以脉状为主岩筒次之;博茨瓦纳岩筒绝大部分为火山口相,中国均为根部相,岩筒地表面积普遍小于前者;(4)奥拉帕A/K1和朱瓦能金伯利岩体是世界上为数不多的主要产出榴辉岩捕虏体和E型金刚石的岩筒之一,而同位于奥拉帕岩群的莱特拉卡内、丹姆沙和卡罗韦岩体与我国郯庐带的金伯利岩体类似,均主要产出地幔橄榄岩捕虏体以及P型和E型金刚石;(5)寻找含矿金伯利岩重点注意以下几点:克拉通内部和周缘深大断裂带是重要的控岩构造;镁铝榴石、镁钛铁矿、铬透辉石、铬尖晶石和铬金红石等是寻找含金刚石金伯利岩重要的指示矿物;航磁等地球物理测量需与土壤取样找矿方法相结合才能取得更好效果;(6)郯庐金伯利岩带、江南钾镁煌斑岩带和塔里木地块是中国重要含矿岩石的找矿靶区,冲积型金刚石成矿潜力巨大。     

金伯利岩:地球深部探测的重要探针

金伯利岩是一种偏碱性的超基性岩,来源于地幔深部,富含挥发份和钾质,属于火成岩类,金伯利岩中主要含有镁铝榴石、金刚石、橄榄石、铬铁矿、铬透辉石、镁钛铁矿,锆石、碳硅石等造岩矿物.同时金伯利岩也被认为是含金刚石最主要的岩石.本文通过文献调研方法,野外现场表明金伯利岩中含有深源包裹体;全球金伯利岩主要分布在俄罗斯、博茨瓦纳、加拿大、安哥拉、南非、刚果民主和纳米比亚;中国金伯利岩主要分布在华北地台,在山东、辽宁、吉林、山西、河南和新疆等地.这些金伯利岩常常与深大断裂甚至地幔深部地质作用关系密切,常出现标志性矿物橄榄石、石榴石、高铬磁铁矿,伴有烃类或氢气.但含金刚石金伯利岩主要沿郯庐断裂带分布,如辽宁瓦房店、山东蒙阴等地.从时代上看,以往认为的早古生代的金伯利岩,更可能都是在早期形成于华北地台之岩石圈底部,而在中生代白垩纪时期才在大规模岩石圈拆沉的地质背景下的以快速上升的,尤其是那些含金刚石的金伯利岩岩管更是快速上升的典型代表,其标型矿物是镁铝榴石、高铬磁铁矿、钙钛矿等.国内辽宁瓦房店含金刚石金伯利岩产于郯庐断裂带东侧,有着与同期金伯利岩相同的岩石矿物学特征,其中的以50号岩管为代表的金刚石矿床是我国重要的战略矿产.金伯利岩及其中的金刚石带来众多直接的深部地幔信息,中国瓦房店、蒙阴一带的金刚石来自上地幔,而一些含硼蓝色金刚石则来自下地幔,不同层圈的金刚石携带不同的标志矿物,以橄榄石为例:来自上地幔金刚石携带的橄榄石为橄榄石;过渡带金刚石携带的主要为瓦兹利石和林伍德石;下地幔的金刚石则为布里奇曼石,它们是深部探测的重要探针.     

我国金伯利岩稀土元素特征

我国山东、辽宁、贵州、山西及河北金伯利岩的稀土总量很高,且变化大。金伯利岩中稀土的球粒陨石标准配分模式为简单的较平滑的线,属LREE极富集型。不同岩体REE含量和配分模式的差异与部分熔融程度、地幔的非均一性、金伯利岩浆早期结晶的石榴石巨晶矿物的含量、壳源物质的混染作用、岩浆中挥发份含量及岩体的产状有关。钙钛矿是金伯利岩中主要的稀土载体矿物,次为磷灰石。     

江苏徐州西村金伯利岩管地质特征及其找矿意义

西村岩管是在苏北地区发现的第一个金伯利岩管,颠覆了苏北地区无金伯利岩的历史。从岩石学、地球化学和伴生矿物等方面分析了西村岩管的地质特征,并进一步探讨其金刚石找矿意义。从区域背景和金刚石形成条件看,西村地区具备了金伯利岩侵位和金刚石矿形成的基本地质条件,而西村岩管为金刚石矿就位提供了母岩条件;西村金伯利岩与山东、辽宁金伯利岩具有相似的地球化学特征,是幔源岩浆低程度部分熔融的产物,且在岩浆上升过程中普遍遭受了壳源物质的混染,后期碳酸盐化现象普遍发育;其相容元素含量与山东金伯利角砾岩相似,均为典型的金伯利岩型配分模式,稀土元素表现为轻、重稀土元素强烈分馏的特征;伴生指示矿物主要为榴辉岩型含铬镁铝榴石、富铬透辉石和富镁铬尖晶石,其特征均表现出含矿金伯利岩的特点。     

中国大陆岩石圈厚度特征研究及其在金刚石原生矿预测中的作用

依据中国大陆三维速度扰动图象,编制了中国大陆现代岩石圈和华北—扬子地台古岩石圈厚度图,并对含与不含金刚石的金伯利岩及钾镁煌斑岩中部分指示矿物和上地幔捕虏体地质特征进行分析,发现岩石圈底部某些地球物理特征与金刚石赋存部位有密切关系。在此基础上,从深部角度讨论了含金刚石的金伯利岩及钾镁煌斑岩时空分布特征,并作了预测研究。     

山东金刚石原生矿成矿规律研究

山东金刚石矿主要分布于蒙阴地区与郯城地区。根据2009年矿产资源利用现状调查资料,山东省有金刚石矿产地9处,其中金伯利岩型原生矿4处,砂矿5处。截止2015年底,山东省保有资源储量为1357万ct,其中常马金刚石原生矿资源量为326万ct,西峪金刚石原生矿资源量为1031万ct。虽然含金刚石的岩石类型很多,但到目前为止,仅有金伯利岩和钾镁煌斑岩（橄榄金云火山岩）可以形成具有工业意义的金刚石原生矿。在山东境内,目前仅有金伯利岩可形成具有工业意义的金刚石原生矿。由于山东金刚石原生矿皆赋存在金伯利岩中,因此研究与寻找金伯利岩是寻找金刚石原生矿的前提条件。鉴于此,对金伯利岩的赋存规律的研究,对金刚石进行成矿预测与指导找矿,都具有极为重要的意义。     

辽宁某地金伯利岩中铬铁矿与金刚石的关系

一、铬铁矿含量与金刚石的关系辽宁某地金伯利岩中普遍含铬铁矿,但含量变化较大,一般含金刚石的贫富与铬铁矿含量成正比。如富含矿(金刚石假品位为5)的五十号岩管中铬铁矿含量平均为372克/吨;中等含矿(金刚石假品位为0.65)的四十二号岩管中铬铁矿含量平均为49克/吨;含矿极贫(金     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

NONMETALS DEPOSITS

正20141520 Bo Ying(Key Laboratory of Metallogeny and Mineral Assessment,MLR,Beijing 100037,China);Liu Chenglin Saline Spring Hydrochemical Characteristics and Indicators for Potassium Exploration in Southwestern and Northern Tarim Basin,Xinjiang(Acta Geoscientica Sinica,ISSN1006-3021,CN11-3474/P,34(5),2013,p.594-602,5 illus.,3 tables,28 refs.)     

MATHEMATICAL GEOLOGY

正20141243Chen Ge(Hangzhou Research Institute of Petroleum Geology,PetroChina,Hangzhou 310023,China);Si Chunsong Study on Sedimentary Numerical Simulation Method of Fan Delta Sand Body(Journal of Geology,     

PROSPECTING EXPLORATION

正20142599Chen Sanming(Guangxi Key Laboratory of Concealed Deposits Exploration,Guilin University of Technology,Guilin541004,China);He Yuzhou Block Model and Reserves Estimation of Panzhihua Iron Deposit Based on 3D Geological Modeling(Journal of Guilin University of Technology,ISSN1674-9057,CN45-1375/N,33(4),2013,p.610-615,9illus.,1table,15refs.)     

STRUCTURAL GEOLOGY

正20140594 Bai Daoyuan(Hunan Institute of Geology Survey,Changsha 410016,China);Zhong Xiang Faults in the Jingzhou Basin and Their Tectonic Settings(Geotectonica et Metallogenia,ISSN1001-1552,CN44-1595/P,37(2),2013,p.173-183,6illus.,59refs.)Key words:basin evolution,tectonic setting,South China In the Upper Paleozoic and Jurassic se-     

STRUCTURAL GEOLOGY

正20141912Cao Hui(State Key Laboratory for Continental Tectonics and Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)Gravitational Collapse and Folding during Orogenesis:A Comparative Study of FIA Trends and Fold Axial Plane Traces(Geology in China,ISSN1000-3657,CN11-1167/P,40(6),2013,p.1818-1828,9illus.,35refs.,with