苏鲁超高压变质带西北缘五莲断裂外侧浅变质花岗片麻岩的地球化学特征与原岩成因研究

五莲杂岩中的正片麻岩主要为正长花岗质片麻岩，少数石英正长质片麻岩，具有适度碱性的演化趋势。以贫CaO、低MgO、高Na2O为特征，岩石中虽然碱度较高，但仍属较强过铝型。这套正片麻岩还表现为较强的轻、重稀土元素分馏程度和强的负Eu异常，尤以强烈富集大离子亲石元素（Rb、Ba、Th、U、K)和亏损高场强元素Ti、Zr、Hf．Nb、Ta(部分样品中Zr、Hf除外)，明显的Ba、P负异常为显著特征。岩石地球化学的总体特征与苏鲁造山带内的花岗质片麻岩有一定的可比性，而与华北克拉通内的前寒武纪正片麻岩明显不同。推测五莲地区正片麻岩的原岩是晚元古代由大陆下地壳富钾的变质玄武质组分部分熔融形成的，母岩浆的演化主要表现为以长石(奥长石和钾长石)的分离结晶为主，其中可能还有少量黑云母和角闪石，以及副矿物锆石和磷灰石的分离结晶。     

胶北早前寒武纪变质基底多期岩浆-变质热事件:来自TTG片麻岩和花岗质片麻岩中锆石U-Pb定年的证据

本文采用LA-ICP-MS技术,对胶北地体TTG片麻岩和花岗质片麻岩中锆石进行系统原位U-Pb定年和稀土、微量元素的分析,发现研究区早前寒武变质结晶基底存在多期岩浆-变质热事件。4件TTG片麻岩和2件花岗质片麻岩锆石样品记录了2909±13Ma、2738±23Ma、2544±15~2564±12Ma和2095±12Ma 4组岩浆事件年龄,以及2504±16~2513±32Ma和1863±41Ma 2组变质事件年龄。结合以往TTG片麻岩和花岗质片麻岩的地球化学及Nd同位素研究发现,约2738Ma的TTG岩浆事件可能代表胶北地体地壳最主要的生长事件,而2544~2564Ma的岩浆事件则可能代表古老地壳重熔的最强烈岩浆事件,约2095Ma岩浆事件则反映了胶-辽-吉构造带内部在该时期与地壳拉张作用有关的岩浆活动。2504~2513Ma是研究区以及华北克拉通早前寒武基底最主要的一期变质热事件,可能与地幔柱(热点)岩浆的底侵作用有关,而TTG片麻岩记录的约1863Ma的变质年龄与研究区基性和泥质高压麻粒岩相岩石记录的麻粒岩相变质时代一致,暗示TTG片麻岩可能也经历了古元古代高压麻粒岩相变质作用,上述研究进一步表明胶北地体在古元古代的确存在一期陆-陆碰撞的重要造山事件。该项研究成果对于进一步深入探讨胶北乃至华北克拉通早前寒武纪变质基底的形成演化、岩浆-变质热事件序列及其构造背景具有重要的科学意义。     

西秦岭党川花岗岩基的岩石化学特征

党川花岗岩基产于祁连与北秦岭造山带结合部位,由9个岩体组成,岩石普遍富K2O。志留纪为闪长岩-石英闪长岩,显著贫SiO2、Na2O,显著富MgO、CaO、TFeO、MnO、P2O5。泥盆纪-侏罗纪岩体为二长-正长花岗岩类,各岩体岩石化学特征较相似,高TiO2、K2O、Na2O,贫MgO、CaO,显示继承性演化规律。志留纪岩体的岩石化学构造环境判别及与其共生的早古生代火山岩相配套,是俯冲造山过程中的岛弧闪长岩类,而泥盆纪熊山沟岩体则是与之密切有关的造山期后陆缘或弧后花岗岩类。其余各岩体是本区造山后与大陆抬升作用以及大陆裂谷作用有关的花岗岩类。     

浙西晚中生代富碱高钾花岗岩类的岩石地球化学特征及构造意义

浙西晚中生代侵入岩分布广泛,在江山、龙游和遂昌三县(市)接壤地带厘定出一套富碱高钾花岗岩类。初步研究表明,以往被认为是I型的该套花岗质岩石应属铝质A型花岗质岩石,在空间上明显受江山—绍兴断裂带及其柘岱口—溪口断裂带的控制,呈北东向带状展布。该岩类由石英正长岩、石英正长斑岩、正长岩、石英二长岩、二长岩、二长花岗岩、花岗岩和花岗斑岩组成,以富碱高钾为显著特点,莱特碱度率 (A.R)为2.14~5.76,过碱指数(AKI值)为0.58~0.96 (平均0.83),偏铝到过铝质 (A/NKC＝0.93~1.30,平均1.05),富含稀土元素 (∑REE＝226.65×10^-6~429.18×10^-6)和较高的Zr＋Nb＋Ce＋Y元素组合值(282×10^-6~826×10^-6,平均482×10^-6),而亏损Ba、Ta、Nb、P、Ti等, 在Na₂O-K₂O>成因类型判别图解中全部落入A型花岗岩区,反映其具A型花岗质岩石的成分特征。洪公岩体与沐尘岩体的Nd同位素模式年龄为1.2~1.6Ga,反映其主要起源于地壳物质的部分熔融。区域背景、构造被动定位特点和地球化学综合分析表明,该套富碱高钾花岗岩类形成于后碰撞构造环境,是早白垩世早期该区重要的构造—岩浆热事件的产物。     

BOOK REVIEWS

Book Reviewed in this article: The City in Cultural Context . John Agnew, John Mercer, David Sopher, eds. Soils and Geomorphology Peter W. Birkeland. Urbanization and Settlement Systems, International Perspectives . L. S. Bourne, R. Sinclair, and K. Dziewoński. eds. An Introduction to Urban Historical Geography . Harold Carter. Overshoot, The Ecological Basis of Revolutionary Change . William J. Catton, Jr. Rivers of the World . Eberhard Czaya. Jewish Communities in Frontier Societies: Argentina, Australia and South Africa . Daniel J. Elazar with Peter Medding. Color in Public Spaces: Toward a Communication-Based Theory of the Urban Built Environment. Kenneth E. Foote. Spatial Statistics and Models. Gary L. Gaile and Cort J. Willmott, eds. Mega-Geomorphology. Rita Gardner and Helen Scoging, eds. Technological Change and Regional Development. Gillespie, ed. The Arid Lands: Their Use and Abuse. R. L. Heathcote. The Location of Industry in Britain. A. G. Hoare. Groundwater as a Geomorphic Agent . R. G. LaFleur, ed. Rural Public Services: International Comparisons. Richard E. Lonsdale and Gyorgy Enyedi, eds. Saving Water in a Desert City. William E. Martin, Helen M. Ingram, Nancy K. Laney, and Adrian H. Griffin. Water Resources: Distribution, Use and Management. John R. Mather. Transnationals and the Third World: The Struggle for Culture. Armand Mattelart. South Hadley, MA: USGS Digital Cartographic Data Standards. R. B. McEwen, R. E. Witmer, and B. S. Ramey, eds. The Ecosystem Concept in Anthropology. Emilio F. Moran, ed. Boulder, CO: Women, Men, and the International Division of Labor. June Nash and Maria Patricia Fernandez-Kelly, eds. Nuclear Power: Assessing and Managing Hazardous Technology. Martin J. Pasqualetti and K. David Pijawka, eds. Mary Somerville and the Cultivation of Science 1815-1840. Elizabeth Chalmers Patterson. An Introduction to Coastal Geomorphology. John Pethick. Late Quaternary Environments of the United States , Vol. 1, The Late Pleistocene. Stephen C. Porter, ed. Planning and Ecology. R. D. Roberts and T. M. Roberts, eds. Regionalism and the Pacific Northwest. William G. Robbins, Robert J. Frank, and Richard E. Ross, eds. Environment and Health. Anthony J. Rowland and Paul Cooper. Sunbelt/Snowbelt: Urban Development and Regional Restructuring. Larry Sawers and William K. Tabb, eds. The Bad Earth. Environmental Degradation in China. Vaclav Smil. Armonk, NY: Voyage into Substance: Art, Science, Nature, and the Illustrated Travel Account, 1760–1840. Barbara Maria Stafford. The Institute of British Geographers: The First Fifty Years. Robert W. Steel. Visions of the Past. Christopher Taylor and Richard Muir. Glacial Lake Agassiz. J. T. Teller and Lee Clayton, eds. The Tule Breakers: The Story of the California Dredge. John Thompson and Edward A. Dutra. The Balkan City 1400–1900. Nikolai Todorov. Explanation, Prediction and Planning: the Lowry model. Michael J. Webber. Mercedes Reales: Hispanic Land Grants of the Upper Rio Grande Region. Victor Westphall. The World Atlas of Revolutions. Andrew J. M. Wheatcroft. The West European City, A Social Geography. Paul White. Urban Elites and Mass Transportation. J. Allen Whitt. Princeton, NJ: Urban Life In Contemporary China. Martin King Whyte and William L. Parish. The Demand for Energy in the Soviet Union. David Wilson. London and Canberra: Rethinking Geographical Inquiry. J. David Wood, ed.     

东秦岭花岗伟晶岩的基本地质矿化特征

伟晶岩是一种特殊的火成岩类,东秦岭是我国重要的花岗伟晶岩分布区和稀有金属成矿区之一,这里广泛发育各种类型花岗伟晶岩,并形成4个大的花岗伟晶岩脉密集区。岩石化学、稀土配分和氧同位素研究结果显示,东秦岭的花岗岩与伟晶岩具有一致或相似的特点。其粗大的矿物组成,表明伟晶岩中富含挥发份并且是在封闭条件较好的地壳中深部形成的,是地壳深部过程的记录和区域侵蚀深度较大的标志。各种类型的花岗伟晶岩具特征的结构、成分和矿化分带现象,反映出深部透岩浆流体的成矿作用。东秦岭花岗伟晶岩受秦岭造山带主造山阶段的加里东期板块俯冲碰撞的影响,是同一板块俯冲碰撞构造体制下由花岗岩母岩浆分异、演化的结果。东秦岭花岗伟晶岩分布面积大、类型全、分异演化强烈、矿化普遍,是我国寻找花岗伟晶岩型稀有元素矿产、铀矿和部分宝石资源的有利地区。     

Petrology and Geochemistry of the Huangshan Granitic Intrusion in Anhui Province, Southeast China: Implications for Petrogenesis and Geodynamics

<正>The Huangshan granitic intrusion in Anhui province,SE China,is tectonically located at the southeastern boundary of the Yangtze Block.Based on the contact relation and the petrography,the Huangshan granitic intrusion can be divided into four stages,from early to late,medium-grained monzogranite,coarse-grained porphyric granite,fine-medium grained porphyric granite,and finecoarse grained granite.All rocks from the Huangshan granitic intrusion display similar petrological and geochemical characteristics,i.e.relatively high SiO_2(75%) and alkali(7.85%-8.59%),low CaO (1%),high Fe-number(FeO_T/(MgO+FeO_T) = 0.93-0.97) and A/CNK(atomic Al/(Ca+Na+K))=1.04- 1.19.They are also enriched in rare earth elements(REE,except for Eu,with a total REE contents ranging from 116 ppm to 421 ppm),high strength field elements such as Zr,Hf,Nb,but depleted in Ba,Sr and Ni.The 10 000×Ga/Al ratios are higher than 2.6,which are consistent with the A-type granitoids.Based on the classification diagrams proposed by Eby,the Huangshan granite can be classified into the A2 group,which is usually believed to be formed under an extensional tectonic setting.Their Nd isotopic compositions suggest that the primary magmas of the Huangshan granite are predominantly derived from the Proterozoic andesitic rocks in the region,and this conclusion is also supported by REE modeling.The systemic investigations on the geochemistry of the Huangshan granitic intrusion can provide significant implications for the understanding of the petrogenesis and the geodynamic regime of southeastern China during the Late-Mesozoic.     

湘中白马山复式岩体成因及其成矿效应

白马山复式岩体位于湘西雪峰山弧形构造隆起带与湘中白马山-龙山-紫云山EW向构造带的交汇处,由水车、龙潭、小沙江和龙藏湾超单元花岗岩组成.锆石LA-ICP-MS U-Pb同位素定年显示,水车、龙潭、小沙江、龙藏湾超单元花岗岩的侵位年龄分别为424.9±2.2Ma、228.2±1.3Ma、225.3±1.1Ma和215.0...     

幔源岩浆持续提供热的有力证据：以湘南九嶷山花岗岩体中暗色包体成因研究为例

湘南九嶷山复式花岗岩体位于南岭西段, 由一个加里东期岩体和四个燕山期岩体组成。其西侧金鸡岭岩体中广泛发育形态多样的暗色包体。本次选取一个2m×2.5m不规则椭球形包体开展研究, 发现它与寄主岩具有较为相近的年龄、矿物组合、地球化学和同位素特征: (1)SIMS锆石U-Pb定年结果显示寄主岩和暗色包体的年龄分别为154.0±1.6Ma和151.4±2.1Ma, 两者在误差范围内一致; (2)两者均以钾长石、石英、斜长石、黑云母、磷灰石、锆石等为主要的矿物组成, 但在矿物组成比例、粒度和形态上有所差距; (3)寄主岩和暗色包体的SiO₂含量分别为70.9%~75.6%和67.3%~68.0%, 两者均富集大离子亲石元素(LILE)而亏损高场强元素(HFSE), 但暗色包体的LILE略低于寄主岩而HFSE略高于寄主岩; (4)寄主岩的ε_Hf(t)值和δ¹⁸O值分别为-8.6~-0.4和7.8‰~8.9‰, 包体的ε_Hf(t)值和δ¹⁸O值分别为-7.0~+1.6和7.3‰~8.9‰。这些特征表明, 金鸡岭暗色包体是由富钾的下地壳玄武质变质火成岩在受到幔源岩浆持续加热后发生部分熔融, 熔融产物注入到已存在于中上地壳的岩浆房中(寄主岩)后发生淬冷作用形成的。尽管寄主岩和暗色包体均是下地壳物质发生部分熔融的产物, 但地壳成分的不均一性导致两者拥有略有差异的同位素和元素组成。沿南岭郴州-临武北东走向断裂带从南向北依次分布有姑婆山、铜山岭、九峰、骑田岭、宝山、锡田花岗质岩体, 其所含暗色包体的ε_Hf(t)和δ¹⁸O值从亏损(+8、5‰)到富集(-8、9‰)变化范围很大, 表明南岭地区暗色包体成因模式具有多样性, 但无论是哪种类型, 幔源岩浆的长期活动持续为下地壳的熔融和岩浆房演化提供热量是一个必不可少的重要因素。