大洋岩石圈拆沉与大陆下地壳拆沉：不同的机制及意义——兼评“下地壳＋岩石圈地幔拆沉模式”

拆沉作用（delamination）是地球科学中一个重要的科学问题。本文认为,大洋岩石圈拆沉和大陆下地壳拆沉是不一样的：（1）拆沉的物质不同。大洋岩石圈拆沉的物质包括大洋地壳、岩石圈地幔甚至一部分软流圈地幔,它们共同进入地幔深部;而大陆下地壳拆沉仅仅限制在下地壳,不包括岩石圈地幔。（2）拆沉的动力不同。大洋岩石圈拆沉是由板块俯冲引起的,是地幔对流的产物,因此是一种快速的主动的拆沉;而下地壳拆沉是由于下地壳加厚使下地壳密度增加引起的,还要求其下刚性的岩石圈地幔转变成塑性的软流圈地幔才有可能发生。因此下地壳拆沉要克服许多阻力才能实现,使拆沉成为一个漫长的过程,是慢速的和被动的拆沉。（3）拆沉的过程不同,大洋岩石圈拆沉是由板块俯冲触发的,俯冲导致碰撞,大洋岩石圈从根部断裂,拆沉进入地幔。大陆下地壳拆沉由地壳加厚开始,使下地壳转变为榴辉岩相;随后,岩石圈地幔减薄,直至全部转化为软流圈地幔;下地壳发生部分熔融,形成大规模的（埃达克质）岩浆,使下地壳榴辉岩的密度大于下伏的地幔,从而引发拆沉。大陆下地壳拆沉不大可能是整体进行的,可能是一块一块地被蚕食,被拆沉的。（4）拆沉后的效液压不同,大洋岩石圈地幔拆沉,使热的软流罪状地幔上涌,从而引发了一系列地质效应;如岩浆活动,地壳抬升,构造松弛以及随后的造山带垮塌等。而下地壳拆沉只引起地壳减薄,高原和山脉垮塌,并不伴有大规模的岩浆活动和地壳抬升等过程。（5）拆沉与岩浆活动的关系不同,主动拆沉导致大规模岩浆活动,而被拆沉是在大规模岩浆活动的基础上开始的。此外,文中还对“下地壳＋岩石圈地幔拆沉”模式提出了质疑,认为该模式有许多难以理解的问题和太多推测的成分,而且与现在保存的地质事实不符。     

鄂尔多斯盆地东部热力作用的期次和特点

盆地深部由于地球内蕴藏的巨大热源和岩石圈放射性元素蜕变热构成的热能,可通过多种热传导方式释放,如岩浆类热流物质向地壳浅部或近地表上部传递热力形成地热异常和热力作用。鄂尔多斯盆地东部晋西挠褶带热力作用发育具有与华北板块早白垩世发生的重要构造转换和岩石圈减薄事件等背景相关,深部岩浆侵入和热力作用事件的发生可使该区地下深处形成许多隐伏的中深成侵入岩或浅成-喷发相岩体及其伴随的热力构造。早白垩世这次强烈的构造热力变动伴有盆地东翼大面积的抬升隆起、吕梁断隆带的翘倾、离石断裂带和晋西挠褶带及西倾大斜坡的形成。以紫金山碱性杂岩体为代表的岩浆热力作用表现为一个多期形成的岩筒、岩床状碱性侵入体,地球化学特点是富碱、Fe,贫Mg;稀土元素含量高,无Eu异常;表现出岩浆侵入有明显的两组方向和多期多阶段侵入或喷发,可侵入到二叠纪—三叠纪地层中。盆地东部火成岩同位素测年数据统计岩浆-热力作用高峰期在110～150Ma。挑选紫金山碱性杂岩体3件单颗粒锆石样数百粒,进行U-Pb同位素SHRIMP测年,其中17组锆石样年龄在125～132Ma,相当于早白垩世。与华北地区早白垩世较普遍的构造热事件具有一致性。此外,还发现有早期(石炭纪—二叠纪)岩浆热力作用事件。构造演化分析显示多期多阶段热力作用特点。鄂尔多斯盆地东部热力作用对盆地油气煤铀多种能源成矿成藏富集研究与勘探评价具有重要意义。     

塔中地区石炭系东河砂岩储层物性影响因素研究

石炭系东河砂岩储层是塔中地区重要的油气产层,通过对岩石铸体薄片、阴极发光薄片、岩心和钻井等资料的综合分析研究认为,岩石颗粒粒度、砂岩厚度以及成岩作用等是影响本区东河砂岩储层物性的主要因素,其中控制储层物性的主要成岩作用有压实作用、胶结作用和溶蚀作用.     

Absorption and Photocatalytic Degradation of Machine Oil by Exfoliated Graphite-Supported Nanometer TiO2 Material

By loading nanometer anatase onto exfoliated graphite with the sol-gel method, exfoliated graphite-TiO2 composite （EG-TiO2） can be prepared, which can adsorb oil and can also degrade oil. In a technologic condition for preparing EG-TiO2, the impregnated number of times is the most important factor to influence oil-adsorbing capability, that is, when the impregnated number of times increases, the amount of saturation-adsorbed oil decreases. The study of EG-TiO2 photocatalytic degradation of machine oil based on the weight-loss method and infrared spectrum method indicates that EG-TiO2 has obvious effect of photocatalytic degradation for machine oil. Its performance is superior to pure nanometer TiO2 powder because nanometer TiO2 in EG-TiO2 has three-dimension laminar structure and comparatively high adsorption capability.     

LA-ICPMS U-Pb Ages of Zircon from Metaleucosomes, Olongbuluke Microcontinent, North Qaidam, and Implications on the Response to the Global Rodinia Supercontinent Assembly Event in NW China

INTRODUCTION The Olongbuluke microcontinent , which wasdisintegratedfromthe northern margin of the Qaidamblock (Lu,2002) ,is composed of a two-fold base-ment with cover strata . The lower basement is themedium- to high-grade Delingha complex and theDakendaban Group, and the upper is the low-gradeWandonggou Group. The Wandonggou Group of theupper basement experienced a Late Mesoproterozoicmetamorphic event (see Yu et al .,1994) ,consistentwith the early isotopic geochronological respo…     

上杭县铁东水库铁锰超标的地球化学作用机理及防治建议

在野外调查及采样分析的基础上,通过综合研究已有资料,对上杭县旧县镇铁东水库中的铁锰质超标原因进行了分析,认为水库中由于残留的有机质与库区内软锰矿层、黄铁矿化岩石在水介质的参与下,发生氧化-还原反应和酸碱反应等一系列现代地球化学作用,形成了一个酸性递增、铁锰离子加快析出的递进的地球化学过程,从而导致水库水中铁锰质超标。     

广西姑婆山里松花岗岩中闪长质包体的地球化学特征及其成因探讨

广西姑婆山里松花岗岩中广泛发育有大量的闪长质包体,包体的野外地质特征、显微结构、矿物组合及化学组成等特征显示其岩浆快速结晶成因。它们的主量元素在相关图上呈不同程度的直线变异关系。在微量元素方面,包体和寄主花岗岩都富含大离子亲石元素和高场强元素。用锆石饱和温度和角闪石成分估算了包体和寄主花岗岩结晶的温度和压力表明,它们的结晶温度和压力条件相近,分别在793—824℃和（3．5—5．1）×10^8Pa范围内。岩石学和同位素地球化学特征也表明,里松包体和寄主花岗岩基本同时结晶,但壳幔比例和来源有所不同。这些特征总体上说明了里松闪长质包体可能是两种岩浆混合时不完全消化的产物     

加强地质勘查实现地质找矿工作新突破

为缓解矿产资源供需紧张对国民经济发展的瓶颈制约作用，国务院出台了“关于加强地质工作的决定”【国发（2006）4号】，河北省作为矿产资源大省，资源对经济的制约作用更加明显，已引起了省委、省政府的高度重视。在新的时期，如何科学地安排地质工作项目，实现地质找矿工作新突破，已成为当代地质工作者思考的重要课题。矿产资源的管理部门，一方面掌握着全省的地勘资金，一方面又苦于没有好找矿项目安排，地质找矿工作应该如何突破？本人根据河北省的成矿地质条件和工作经验，就我省紧缺矿种资源的找矿工作，谈一点个人看法，以供参考。     

“第34届国际水文地质大会”即将在京召开

水文地质学作为与国民经济发展密切相关的应用学科，在世界各国水资源调查、保护和管理方面发挥着重要的支撑作用。2006年是国际水文地质学家协会（IAH）成立五十周年。因此，2006年10月09日-2006年10月13日国际水文地质学家协会和中国国土资源部将在北京市联合举办“第34届国际水文地质大会”。这将是继1988年中国在桂林市成功举办“第21届国际水文地质大会”之后，再次在中国举办国际水文地质大会。     

Possibility of degradation of phenylarsonic acid in the presence of ferrihydrite

Although inorganic species are predominant in natural systems, but there are many kinds of organoarsenic species such as methylated and phenylated arsenic compounds. Phenylarsonic acid （PA） is a degradation product of organoarsenics used for chemical warfare agents, which has been detected in well water at the disposal site of the agents in Japan. There are few reports studying behavior of PA in soil. In this study, PA was adsorbed onto ferrihydrite and its chemical forms were determined using high performance liquid chromatography connected to inductivity-coupled plasma mass spectrometry （HPLC-ICP-MS）. 100 mg/kg of PA was mixed with 0.03 g of 2-line ferrihydrite. For each suspension, pH was adjusted by HNO3 or NaOH. Each sample was incubated for more than 19 hours and the final pH was measured. After filtration, the chemical form of arsenic in the filtrate was measured using HPLC-ICP-MS. In addition, ferrihydrite separated by filtration was dissolved by 3 ml of 0.5 M HCI and the arsenic species in the solution was detected by HPLC-ICP-MS （column： Tosoh TSKgel SuperlC-AP, eluent： 0.01 M HNO3）. It was verified that PA is not degraded by heating in 0.5 M HCl solution. At pH 3.1, any arsenic compounds were not detected from the solution, because almost all arsenic species were adsorbed onto ferrihydrite at lower pH. At pH= 12, however, 7%-10% of inorganic arsenic was detected in the solution. In solid phase, there are some problems to determine the precise ratio of inorganic and organic species. When the solution includes Fe ion at 0.01 M level, the retention time of arsenic species drifted compared to those in standard solution, which makes it difficult to determine precisely the arsenic species adsorbed on ferrihydrite. Therefore, more study is needed to determine the ratio of inorganic and organic species in the system.