Mantle processes during ocean formation：Petrologic records in peridotites from the Alpine－Apennine ophiolites

Mantle peridotites were early exposed at the sea-floor of the Jurassic Tethys derived from the subcontinental mantle of the Europe-Adria system. During continental rifting and oceanic spreading, these lithospheric peri-dotites were percolated via diffuse reactive porous flowby melt fractions produced by near-fractional melting of the upwelling asthenosphere. Ascending melts inter-acted with the lower lithosphere, dissolving pyroxenes and precipitating olivine, and crystallized at shallower levels in the mantle column causing melt impregnation.Subsequent focused porous flow formed replacive dunitechannels, cutting the impregnated oeridotites, which were conduits for upward migration of MORB-type liq-uids. Melt migration produced depletionlrefertilization and significant heating of the percolatedlimpregnated mantle, i.e the thermochemical erosion of the litho-sphere. Impregnated and thermally modified lithos-pheric mantle was cooled by conductive heat loss dur-ing progressive lithosphere thinning and was intrudeaby MORB magmas, which formed Mg-rich and Fe-richgabbroic dykes and bodies. Alpine-Apennine ophiolitic peridotites record the deep-seated migration of melts which changed their compositions and dynamics during the rift evolution. The thermochemical erosion of the lithospheric mantle by the ascending asthenospheric melts, which induces significant compositional and rhe-ological changes in the lower lithosphere, is a major process in the evolution of the continent-ocean transi-tion towards a slow spreading oceanic system.     

浅谈火山作用

地壳深处的岩浆喷出地壳便产生了火山现象，所引起的全部地质过程称为火山作用。火山喷发是一种极为壮观而令人生畏的自然现象，介绍了火山喷发主要的3种形式、火山作用造成的灾害类型和中国的火山特点，以及自全新世以来我国有过喷发活动的8个主要活火山。提出了要加强认识火山的活动规律、形成过程、喷发机理，开展监测，采取对策，防灾减灾。     

广西中三叠统浊流流向及坡向

通过对广西中三叠统浊积岩系中溢堤流沉积的识别,结合同一鲍马层序Tc段斜层理倾向与其底部槽模走向不一致的分析,以及横向冲刷模、U形障碍冲刷痕等冲蚀构造、大型滑动模等压刻构造的认识,筛选出宽阔水道充填沉积、扇状体及分支水道沉积中底模构造的指向数据,来指示浊流主体流向,并区分出溢堤流流向。从而确定了本区中三叠世时的浊流主体流向为NW向,平均为300°。根据滑塌沉积中滑塌包卷层轴面、滑塌面的测定,确定凤山县金牙处的古坡向平均为322°,与浊流主体流向基本一致。还认为中三叠世时右江盆地沉积物源来自桂东和桂东南蚀源区,海水由其南的越南境内进入。     

TL dating of loess in China

TL ages of 56 loess samples collected from Xinjiang and the middle reaches of the Yellow River were determined by using fine-grained quartz and man-made light source bleaching techniques.The results indicate that :1.The well-preserved loess sections in Xinjiang began depositing 400000 a ago.The loess/paleosol series may be comparable with that observed in the middle reaches of the Yellow River but the depositing time was probably delayed by 30000-50000a.2.The bottom boundary age of the Malan loess varies from one place to another.The TL dates can be divided into two group:70000-130000 a and 30000-50000 a.The TL data are con-sistent with the appearance of two warmer climate periods since the Pleistocene,indicating obvious regional differences in stratigraphic development of loess,i.e.,paleosol occurred in the warm climate period in the same location,but loess was deposited in other locations.The initial age of loess deposition tends to become older from west to east and from south to north .In contrast ,the cold cli-matic belt showed an opposite trend.The TL ages of loess provide strong evidence for the Quaternary stratigraphy throughout geological times and the shift tendency of climatic belt.3.The depositing rate of the Malan loess along the middle reaches of the Yellow River varies from place to place but the TL age shows a linear relationship with the depositing thickness.The de-positing rate of loess in the north is higher than that in the south,suggesting that loess materials are derived from desert areas of northern China.     

准噶尔盆地腹部Z2井三叠系地层及沉积特征

对准噶尔Z2井三叠系各组的岩性、电性特征进行了详细解释与描述,对各组的孢粉、大孢子组合特征展开了讨论,提出了该井三叠系地层划分为自碱滩组、克拉玛依组和百口泉组,且将其与邻区钻遇的三叠系进行了横向及纵向对比。在此基础上,通过对测、录井资料的精细解释,并借鉴前人的区域沉积相研究成果,探讨了该区三叠纪沉积环境。     

东秦岭二郎坪群中火山成因块状硫化物矿床地质地球化学特征及其成因讨论

二郎坪群是东秦岭造山带重要的组成部分,其火山建造中广泛发育有火山成因块状硫化物(VMS)矿床.文章总结并分析了南阳盆地东、西两侧二郎坪群中3个典型矿床(刘山岩、水洞岭和上庄坪)的研究资料,把二郎坪群VMS矿床分为3类:Zn-Cu型矿床(刘山岩矿床);Zn-Cu型与Zn-Pb-Cu型矿床(水洞岭矿床);Zn-Pb-Cu型矿床(上庄坪矿床).从刘山岩矿床到水洞岭矿床,再到上庄坪矿床,铜的含量减少,铅的含量增多.二郎坪群VMS矿床矿石富集LREE、Ce负异常及Eu正异常,说明矿床为热液成因.石英和重晶石中流体包裹体的氢氧同位素特征表明,成矿流体主要来自建造水,南阳盆地以西,矿床成矿流体中伴有较多古大气降水.矿石的硫同位素特征说明,二郎坪群VMS矿床中的硫可能为地幔岩浆硫和海水硫的混合硫.围岩与矿石的铅同位素组成基本一致,说明矿石和围岩可能来源于相似的物源区,成矿元素主要来源于地幔或下地壳深源物质,而水洞岭矿床明显有上地壳浅源物质的混染.研究表明,南阳盆地以西的水洞岭和上庄坪矿床可能形成于大陆边缘海环境,盆地规模较小,受陆源物质影响较大;而南阳盆地以东的刘山岩矿床可能形成于远洋盆地,盆地到达成熟阶段.用地震泵模式可解释二郎坪群VMS矿床的成因机制.     

山东省济宁强磁异常区深部铁矿初步验证及其意义

山东省济宁磁异常是一个重、磁同源体,面积大于100 km2,磁异常峰值为3800nT。钻探验证在孔深1041.57～1796.54m位置发现铁矿体,矿体总厚度74.04～220m,磁性铁平均品位15.89～25.19%。矿石类型有条带状方解磁铁石英岩和条带状磁铁石英大理岩,矿石的主要组成矿物为石英、方解石、磁铁矿、磁赤铁矿、菱铁矿。矿体产于济宁岩群浅变质岩系中,矿床特征与条带状铁建造（BIF）铁矿或鞍山式铁矿有明显区别,铁矿成因类型属与千枚岩、变质中酸性火山岩、大理岩有关的沉积变质型铁矿床。该区铁矿资源潜力巨大。     

松辽盆地嫩江组白云岩形成机理——以松科1井南孔为例

松科1井是中国大陆第一口以白垩系地层为主的全取心科学探井,由松科1井南孔和松科1井北孔两个钻孔组成.在松科1井南孔岩心精细描述的过程中发现嫩江组地层中发育层状白云岩和椭球状白云岩,共62层.白云岩结核垂向截面的透镜形状、结核内部上凸下凹两端收敛的层理特点以及在显微镜下观察到的白云石的雾心亮边结构和泥灰岩被局部交代产生的"豹斑状"白云石聚集均显示嫩江组白云岩是湖相泥灰岩在准同生期被交代的产物.白云岩的形成机制是在晚白垩世松辽盆地海侵背景下Mg2 在准同生期交代由浊积事件、介形虫灭绝事件所带来的泥灰岩沉积而成.     

“第十届全国古地理学及沉积学学术会议”在成都召开

由中国矿物岩石地球化学学会岩相古地理学专业委员会、中国矿物岩石地球化学学会沉积地质专业委员会、中国地质学会沉积地质专业委员会、中国地质学会地层古生物专业委员会、中国地质学会石油地质专业委员会和中国石油学会石油地质专业委员会主办,中国石油化工股份有限公司勘探南方分公司和中国石油化工股份有限公司西南油气分公司承办,中国石油大学(北京)、成都理工大学和中国石油勘探开发研究院协办的"第十届全国古地理学及沉积学学术会议",2008年9月22-24日在成都召开.这次会议是我国古地理学及沉积学领域的一次盛会.与会人员来自中科院、高校、石油系统、地矿系统、煤炭系统、核工业系统和出版系统等近40个单位,共185人.其中,年龄最大的82岁,最小的22岁.