关于C型埃达克岩成因的再探讨   总被引：5，自引：0，他引：5  

张旗 《岩石矿物学杂志》2011,30(4):739-747

文中回顾了对C型埃达克岩认识的过程,归纳了C型埃达克岩的产出特征、存在问题、研究意义及今后研究的方向,指出中国东部C型埃达克岩是高钾钙碱性的,可能是变质的中钾和高钾的中基性岩在高压条件下部分熔融形成的。不同于O型埃达克岩,它的成因、源区特征、熔融机制,是今后研究的重点,需要大量实验研究的支持。钾质的C型埃达克岩是新的大陆构造学研究的切入点,比钠质的O型埃达克岩具有更重要的意义。  相似文献   

Symposium On Sediment Storage In Rivers And Estuaries     

《The Professional geographer》2013,65(4):487-488

Book Reviewed in this article:

Geographical Aspects of Health and Disease in India. Rais Akhtarand A.T.A. Learmonth, eds.

Antarctic Treaty System: An Assessment. Proceedings of a Workshop at Beardmore South Field Camp, Antarctica.

American Electoral Mosaics. J. Clark Archerand Fred M. Shelley.

Kompas op Suidwes-Afrika/Namibie. W.S. Barnard, ed.

Jerusalem in the 19th Century: The Old City. Yehoshua Ben-Arieh.

The World as a Total System. Kenneth E. Boulding.

A Social History of Housing 1815–1985, Second Ed. John Burnett.

Human Migration. W.A.V. Clark.

Regional Population Projection Models. Andrei Rogers.

The State of Population Theory: Forward from Malthus. David Colemanand Roger Schofield, eds.

Imagining Tomorrow: History, Technology and the American Future. Joseph C. Corn, ed.

Swidden Agriculture in Indonesia: The Subsistence Strategies of the Kalimantan Kantú. Michael R. Dove.

Glacial Geologic Processes. David Drewry.

Physics of Desertification. Farouk El-Bazand M.H.A. Hassan, eds.

Housing the Homeless. Jon Ericksonand Charles Wilhelm, eds.

Settlement Patterns in Missouri: A Study of Population Origins, with a Wall Map. Russel L. Gerlach.

Desert Development: Man and Technology in Sparselands. Yehuda Gradus, ed.

Nuclear Winter. The Evidence and Risks. Owen Greene, Ian Percivaland Irene Ridge.

The Take-off of Suburbia and the Crisis of the Central City. Günter Heinritzand Elisabeth Lichtenberger, eds.

Regional Input-Output Analysis. Geoffrey J. D. Hewings.

Spatial Transportation Modeling. Christian Werner.

The Atlas of Georgia. Thomas W. Hodlerand Howard A. Schretter, eds.

Latin America. 5th ed. Preston E. Jamesand C.W. Minkel.

Applied Remote Sensing. C.P. Lo.

Localities, Class, and Gender. The Lancaster Regionalism Group.

Urban Social Movements: The City after Castells. Stuart Lowe.

Politics and Method. Doreen Masseyand Richard Meegan, eds.

Land Use. A. S. Mather.

The Kingdom of Coal. Donald L. Millerand Richard E. Sharpless.

The Presidio and Militia on the Northern Frontier of New Spain, A Documentary History, Vol. 1: 1570–1700. Thomas H. Naylorand Charles W. Polzer, S.J., comps. andeds.

Nuclear Power: Siting and Safety. Stan Openshaw.

The Central African Republic: The Continent's Hidden Heart. Thomas O'Toole.

Environmental and Dynamic Geomorphology. Márton Pécsi, ed.

Remote Sensing Principles and Interpretation. Floyd F. Sabins, Jr.

Acid Rain and Friendly Neighbors: The Policy Dispute between Canada and the United States. Jurgen Schmandtand Hilliard Roderick, eds.

Earth's Changing Surface: An Introduction to Geomorphology. M.J. Selby.

International Migration: The Female Experience. Rita J. Simonand Caroline B. Brettell, eds.

On Geography and Its History. D.R. Stoddart.

Transportation Networks: A Quantitative Approach. D. Teodorovic.

Processes in Physical Geography. R.D. Thompson, A.M. Mannion, C.W. Mitchell, M. Parry, J.R.G. Townshend.

Imaging Radar for Resources Surveys. J.W. Trevett.

Dominance and Affection: The Making of Pets. Yi-Fu Tuan.

Capturing the Horizon. The Historical Geography of Transportation since the Transportation Revolution of the Sixteenth Century. James E. Vance, Jr.

Nations at Risk: The Impact of the Computer Revolution. Edward Yourdon.  相似文献   

囊谦盆地新生代高钾岩浆岩的地球化学特征:岩石成因及其构造意义   总被引：2，自引：2，他引：0  

程锦  夏斌  张玉泉 《大地构造与成矿学》2008,32(3)

位于青藏高原东缘的囊谦高钾岩浆岩(37.5~38.3Ma)SiO2含量49.9%~66.6%,富集LREE和LILE(K、Rb、Sr、Ba、Th),亏损HREE和HFSE(Nb、Ta、Ti等),在微量元素蛛网图上Nb、Ta、Ti显示负异常。囊谦富钾岩浆岩的Sr-Nd同位素变化范围窄(87Sr/86Sr=0.70425~0.70548,143Nd/144Nd=0.51256~0.51273),显示出EMI富集趋势。通过对囊谦高钾岩石的元素和同位素地球化学的研究,认为其源区同时受到了因俯冲而进入地幔的地壳物质及蚀变洋壳析出流体的改造和交代作用。这套钾质岩石的形成是受到了特提斯洋俯冲消减,进而印度大陆与欧亚大陆碰撞,以及之后发生的岩石圈由挤压转为拉张并由此产生的软流圈上涌等一系列动力体系的控制。  相似文献   

河北康保地区花岗岩独居石电子探针定年   总被引：5，自引：1，他引：5  

王鑫琳 张臣刘树文  舒桂明 《岩石学报》2007,23(4):817-822

已有年代学研究表明,康保地区西阿公单元含石榴二长花岗岩形成于中元古代。我们采用近年来新发展的独居石电子探针Th-U-总Pb定年方法对康保地区西阿公单元十硼地区变质细粒含石榴二长花岗岩样品中的独居石开展了电子探针进行测年分析,计算方法为Suzuki和Adachi等提出的方法。独居石年龄峰值分别为252Ma,265Ma,281Ma和322Ma,表明西阿公单元含石榴二长花岗岩形成时代不是中元古代,其侵位时间应为二叠纪。这一新的年代学结果与Sengor和王荃推测的华北板块与西伯利亚板块"晚二叠世碰撞"的模式一致。康保地区西阿公单元含石榴二长花岗岩具过铝花岗岩特征,代表古蒙古洋消失,是华北板块与西伯利亚板块碰撞造山阶段多期岩浆作用的结果,为确定古亚洲洋的闭合时间提供了重要依据。  相似文献   

Aoyitake plagiogranite in western Tarim Block, NW China: Age, geochemistry, petrogenesis and its tectonic implications   总被引：1，自引：2，他引：1  

ZHANG Chuanlin  YU Haifeng  YE Haimin  ZHAO Yu  ZHANG Dongsheng 《中国科学D辑(英文版)》2006,49(11):1121-1134

SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block, NW China. The plagiogranite intruded the Middle Pro- terozoic and Lower Carboniferous with an exposure area of ca. 60 km2 and crystallized at 330.7±4.8 Ma. Rock types mainly include tonalite, trondhjemite and minor amounts of diorite and quartz-diorite. Feldspars in the rocks are dominated by oligoclase-andesine, and minor perthite observed locally. The granites are sodic with Na/K ratios (molar) between 4 and 87. Total REE (50-220 ppm) show a clear positive correlation with SiO2. There is no LRRE/HREE fractionation (LaN/YbN=0.5-1.5), me- dium negative Eu anomalies (δ Eu=0.3-0.6), high Y content and low Sr/Y ratio (~1.0). These granites exhibit relatively juvenile Nd T2DM model ages of 470 to 580 Ma and positive εNd(331 Ma) values of 6.23 to 7.65. The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites. However, the regional geology, especially its scale, precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma. We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca. 50% partial melting of the juvenile basaltic crust. The primary magma experienced intensive frac- tionational crystallization, and intruded into the middle to upper crusts to form the granite pluton. In combination with the previous regional geological data, it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.  相似文献   

Organic geochemistry and source potential of the lacustrine shales of the Upper Triassic - Lower Jurassic Kap Stewart Formation, East Greenland     

Gregers Dam  Flemming G. Christiansen 《Marine and Petroleum Geology》1990,7(4)

The Upper Triassic — Lower Jurassic Kap Stewart Formation (Jameson Land, East Greenland) has been studied by a combination of sedimentological and organic geochemical methods (LECO/Rock Eval, sulphur, gas chromatography) in order to assess the hydrocarbon source potential of the abundant and extensive lacustrine shale intervals present in the formation.The organic matter in the shales is a mixture of algal and higher plant remains (type I and III kerogen). An organic assemblage dominated by algal material, having a rich oil potential, occurs in an interval approximately 10–15 m thick in the uppermost part of the formation. This interval has an organic carbon content up to 10% and Hydrogen Index values up to 700. The interval is consistently traceable along the exposed margins and the central part of the basin. The deposition of the uppermost shale interval coincided with the largest expansion of the lake, during a period with a stratified water column and anoxic bottom-water conditions.Locally the rocks exposed are thermally postmature due to the thermal influence of dolerite sills which intruded the Kap Stewart Formation in Tertiary time. However, the organic-rich shale interval is beyond the influence of the sills and indicates a maturity prior to or in the early stages of oil generation.Calculations of the generative potential of the lacustrine source rocks suggest that significant amounts of petroleum may have been generated in those sediments which have undergone sufficient burial in the southern and central part of the basin. Here, the contemporaneously deposited delta front and barrier island sandstones can thus be considered as potential targets for future hydrocarbon exploration. This type of play may also be of importance in other North Atlantic basins with a similar basin history.  相似文献   

南方水稻复种指数变化对国家粮食产能的影响及其政策启示   总被引：7，自引：1，他引：7  

蒋敏  李秀彬  辛良杰  谈明洪 《地理学报》2019,74(1):32-43

中国南方地区水稻生产的变化对国家粮食安全具有重要影响。本文利用Landsat数据提取1990-2015年南方地区水稻种植制度分布及变化,并分析其对粮食产能的影响。结果表明：① 1990-2015年,水稻复种指数从148.3%下降到129.3%,双季稻改种单季稻（“双改单”）损失的播种面积为253.16万hm²,区域上以长江中下游地区变化最为突出。南方地区水稻种植制度整体呈现由北向南“双退单进”的变化格局;② 1990-2015年,“双改单”导致全国水稻产量减少6.1%,粮食产量减少2.6%。水稻主产区湖南省和江西省以及经济发展较好的浙江省因“双改单”水稻减产幅度较大,均超过13%;③ 充分利用“双改单”稻田的粮食产能相当于新增耕地223.3万hm²,为2001-2015年通过土地整治项目新增耕地总量的54%,是2016-2020年全国新增耕地规划目标的1.7倍,可节省约1674.4亿元新增耕地开垦费用。因此,与其追求低质量的“新”耕地,不如充分利用已有的高质量“旧”耕地,政府应转变耕地占补平衡的考核方式,将因提高复种指数增加的播种面积纳入补充指标。  相似文献   

桂北融水地区钾镁煌斑岩Ar- Ar年代学、地球化学特征及其构造意义     

林木森  彭松柏  吴长锋  王新宇  吴祥珂 《地质学报》2019,93(8):1985-1997

桂北地区发育较多的钾镁煌斑岩脉,可能为该区近源金刚石重砂矿的母岩,对于其形成时代一直是长期争议悬而未决的重要地质问题。本文研究表明,融水地区金云钾镁煌斑岩的金云母(斑晶、基质) 40 Ar- 39 Ar冷却封闭年龄为203~204 Ma,表明其形成于晚三叠世。岩石SiO 2为55. 68%~56. 85%,高钾(K 2O/Na 2O=1. 87~3. 06)、高Mg # (71. 90~73. 20)、轻稀土富集、重稀土相对亏损,轻重稀土分异明显,Eu略亏损,富集大离子亲石元素,亏损高场强元素,地球化学特征表明其来源于俯冲流体交代的富集地幔特征。上述研究表明,扬子克拉通东南缘桂北地区中生代岩石圈地幔为经历俯冲流体交代的富集地幔,并于晚三叠世经历了重要的岩石圈伸展减薄构造事件,其形成可能与古太平洋板块平板式俯冲有关。  相似文献   

华北克拉通南缘古元古代末(～1.84Ga)垣头A-型花岗岩成因及其构造意义     

邓小芹  彭头平  赵太平  丘志力 《岩石学报》2019,35(8):2455-2469

在华北克拉通陆续发现有大量的古元古代末-中元古代早期A-型花岗岩,它们具有独特的地球化学特征和特定的形成条件,可为进一步了解A-型花岗岩的岩石成因以及华北克拉通由结晶基底的形成向稳定盖层发育时期构造环境的转折提供重要依据。本文对华北克拉通南缘产出的垣头花岗岩体进行了岩石学、锆石U-Pb年代学、元素地球化学和Nd-Hf-O同位素研究。结果表明,垣头岩体岩石类型主要为正长花岗岩,形成时代为1841±4Ma;全岩样品具有较高的铁(FeO~T/(FeO~T+MgO)=0. 75～0. 86)、富碱(K_2O+Na_2O=8. 11%～9. 13%,K_2O/Na_2O 1)、低MgO (0. 28%～0. 56%)、P_2O_5(0. 04%～0. 08%)和MnO(0. 03%～0. 04%),富含大离子亲石元素(如Rb、Th、U、K)、亏损高场强元素(Nb、Ta、Zr、Hf),具有Eu、Sr负异常,高10,000Ga/Al比值( 2. 76)、准铝质-弱过铝质且不含碱性暗色矿物,属于铝质A-型花岗岩;全岩εNd(t)=-4. 68、tC DM=2. 70Ga,锆石εHf(t)=-12. 0～-4. 71、tC8DM=3. 22～2. 78Ga,锆石δ1O=5. 4‰～6. 5‰(加权平均值为6. 1‰),指示它们是古老基底物质部分熔融的产物。结合区域上的地质特征和研究资料,我们认为垣头A-型花岗岩体形成于碰撞后的伸展环境,标志着华北克拉通1. 85Ga前后的造山运动的结束。  相似文献   

城市"新经济"发展的空间效应及其启示——以西安市为例   总被引：1，自引：0，他引：1  

王慧 《地理研究》2007,26(3):577-589

以知识为基础、以计算机与信息技术为依托、技术与制度创新驱动、兼跨第二与第三产业并以服务业居重、高度外向而趋于全球化的当代"新经济"的兴起,正从诸多方面影响和改变着城市。本文以西安市为实证分析案例,依据对"新经济"内在禀赋特性的认识,从城市"产业区"格局重构、城市办公楼宇设施增长、高新技术产业区的CBD化、产业与居住功能分区的模糊化、城市经济与社会空间的极化等方面对城市"新经济"发展的空间影响效应进行了分析,并就其对于城市规划与决策的启示予以探讨。  相似文献