佛子岭群逆时针P-T轨迹对大别碰撞造山带构造演化的探究     

杨根山  石永红  唐虎  李秋立  侯振辉 《岩石学报》2020,36(12):3654-3672

佛子岭群位于大别造山带最北缘，处于华北和扬子两大板块结合部位，构造位置十分关键，是解析两大板块精细耦合过程和探究大别造山带晚古生代构造事件的重要单元。然而，由于长期以来佛子岭群一直被视为"浅变质"复理石沉积单元，因而对其变质演化过程的解析较为薄弱，制约了对大别造山带形成过程的全面理解。本次通过对老虎场-龚店地质剖面细致的观测，石榴黑云母片麻岩精细的岩相学、矿物化学分析、热力学评价和年代学研究，建立了佛子岭群一个逆时针P-T变质演化型式。研究显示，佛子岭群记录了Ⅰ、Ⅱ、Ⅲ和Ⅳ四个变质阶段，温压变化依次为：①T=658~663℃、P=1.08~1.16GPa→②T=755~762℃、P=1.21~1.45GPa→③T=549~554℃、P=1.08~1.19GPa→④P_标定=0.3~0.6GPa、T=477~499℃，①至③为近等压升温和降温过程，③至④则表现为近等温降压型式。锆石U-Pb定年显示了1484±64Ma~1180±192Ma、995±35Ma~606±14Ma和370±14Ma~331±8Ma三组年龄，前两组代表了碎屑锆石年龄；第三组共计7颗锆石，年龄集中，Th/U比值0.01~0.03，加权平均年龄为344±11Ma，代表了主期变质年龄。结合此次地质剖面结构特征和岩石类型，以及前人白云母⁴⁰Ar-³⁹Ar的270~255Ma变质年龄，表明佛子岭群记录了两期变质事件，早期为晚古生代的拉张背景下的岛弧根部变质，晚期为晚古生代末的较为快速抬升构造热事件，并据此推测大别造山带可能为增生和碰撞复合型造山带。  相似文献   

海南岛石炭纪双峰式火山岩及其板块构造背景   总被引：4，自引：2，他引：4  

夏邦栋  施光宇 《岩石学报》1991,7(1):54-62

海南岛西部的石炭纪火山岩为一套大洋拉斑玄武岩-流纹斑岩的双峰式火山岩。玄武岩中的不相容元素和稀土元素的丰度和比值,以及稀土分配模式与大陆裂谷的拉斑玄武岩的地球化学特征一致,说明海南岛晚古生代裂谷作用的存在。玄武质岩浆来源于地幔深部,演化程度较低,受下地壳物质混染。流纹质岩浆不是玄武岩浆结晶分异产物,而是受裂谷区高热流影响,由陆壳部分熔融形成。  相似文献   

黑河实验（HEIFE）能量平衡和水汽输送研究进展   总被引：16，自引：0，他引：16  

胡隐樵 《地球科学进展》1994,(4)

总结了黑河实验中能量和水汽交换特征研究进展。建立了绿洲同包围它的沙漠环境相互作用基本模型，即绿洲的冷岛效应和沙漠的逆湿现象。绿洲对沙漠观测的主要干拢是沙漠能量平衡中的一个小量，即可以忽略不计的潜热通量。所以黑河实验沙漠和戈壁站能量平衡的基本特征对干旱地区有一定的代表性。  相似文献   

海南岛砖红壤中重金属元素的分布特征及其环境效应   总被引：10，自引：1，他引：10  

赵志忠  毕华 《矿产与地质》2005,19(1):7-11

选择海南岛占地面积广、发育典型的砖红壤作为研究对象，探讨砖红壤发育过程中重金属元素的组成特征，分析不同地区砖红壤剖面重金属元素含量的纵向变化规律，厘定不同剖面不同层位重金属元素的富集规律及其成因，并阐述土壤重金属污染的环境效应及其与人类健康之间的相关关系。  相似文献   

祁连山扎麻什基性杂岩体岩石地球化学特征及其大地构造意义   总被引：4，自引：7，他引：4  

刘传周  肖文交袁超 闫臻 《岩石学报》2005,21(1):57-64

青海省祁连县扎麻什基性杂岩体侵位于寒武一奥陶纪地层中。岩体以辉长岩为主，并伴有超基性岩，辉石岩，角闪石岩与闪长岩出露。岩石地球化学研究表明，该岩体是由钙碱性岩浆经不同程度的分离结晶作用形成的。岩石具富集大离子亲石元素(LILE)而亏损高场强元素(HFSE)，并具有明显Nb和Ta负异常。结合该岩体与北侧清水沟一百经寺俯冲杂岩的空间分布关系，表明该杂岩体是形成于北祁连洋壳向南俯冲形成的岛弧环境。  相似文献   

南海东岛湖泊沉积物中的生态环境记录   总被引：7，自引：2，他引：7       下载免费PDF全文

刘晓东  孙立广  赵三平  尹雪斌  谢周清  罗泓灏 《第四纪研究》2005,25(5):574-584

东岛牛塘为目前在西沙群岛少见的淡水湖泊,发育保存完好的沉积物。文章通过对一根长126cm的沉积柱开展多方面的沉积学分析,包括沉积物的岩性特征,反映碳酸盐含量的白度、CaO和LOI950℃以及反映有机质含量的TOC,TN,TS和LOI550℃等地球化学指标随深度的变化特征,沉积物和环境介质的碳、氮同位素的对比分析,沉积物的稀土元素和Sr,F,P,Se等元素地球化学特征。结果认为:该湖泊沉积剖面自上而下可分成3个具有明显不同沉积学特征的沉积单元,其中25～96cm的沉积层明显地受到了海鸟粪的影响。识别出的海鸟粪土沉积层,为进一步研究历史时期岛屿鸟类生态系统和气候演化提供了良好的信息载体。  相似文献   

Sediment movement rates and processes on cinder cones in the maritime Subantarctic (Marion Island)     

Stephen Dale Holness 《地球表面变化过程与地形》2004,29(1):91-103

Sediment transport in the scoria areas of Marion Island is primarily the result of needle‐ice‐induced frost creep associated with diurnal soil frost cycles. Clasts move most rapidly in ?ne textured areas (532 mm a^?1; SD 382), more slowly in stony areas (161 mm a^?1; SD 179), and most slowly in blocky areas (26 mm a^?1; SD 23). Movement rates increase with increasing frost susceptibility of sediments, slope angle and altitude. The heave of dowels indicates that frost heave is active in all the scoria areas examined. The depth of effective frost heave increases with increasing altitude, with frost heave being restricted to the upper 100 mm of the soil in low altitude areas (<200 m). The heave of 150 mm dowels at the higher altitude sites provides evidence for segregation ice formation at depths greater than those associated with needle ice and diurnal soil frost cycles. Vertical movement pro?les show a concave downslope pro?le, with sediment movement rates being most rapid at the soil surface and decreasing rapidly with depth. This pro?le shape is typical of areas dominated by diurnal freeze–thaw cycles and needle ice. The capture of sediments moving downslope in troughs and the sampling of material lifted by needle ice, suggest that sediment transport by needle ice under present conditions is extremely effective. Observations suggest that although both ?ne material and clasts are transported downslope, some preferential transport of clasts occurs. Experiment results and observations of soil frost processes suggest that frost creep associated with needle ice activity is the dominant slope process in the scoria areas of Marion Island. Other slope processes such as slopewash and debris ?ows appear to play a relatively minor and localized role in sediment transport. It is suggested that needle ice activity is likely to be the dominant geomorphic agent in other areas of the Subantarctic with similar climatic characteristics to Marion Island. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

海南抱伦金矿床控矿构造特征及其对金矿化的控制作用   总被引：4，自引：0，他引：4       下载免费PDF全文

陈柏林  李中坚董 诚 丁式江 舒 斌廖香俊  董法先傅杨荣 《中国地质》2004,31(2):139-146

抱伦金矿床是海南省新近发现的大型金矿床之一，属于成生于印支期受构造控制的岩浆热液型金矿床。矿区出露下志留统陀烈组浅变质岩系与白垩系红色碎屑岩，西北侧分布印支期花岗岩。北北东向豪岗岭断裂与其上盘的北北西向断裂破碎带组成矿区基本构造格架。磁组构分析显示矿区千枚岩以压扁变形占绝对优势，主压应力近东西向，矿化热事件前的构造变形较强，矿化之后的构造变形较弱。矿化期构造应力场为近东西向拉伸(主压应力近南北向)。北北西向断裂破碎带是主要赋矿(含矿)构造，对矿体的空间分布、形态产状起重要的控制作用。  相似文献   

海南岛烟塘岩体的成因及其构造意义     

云平  谢盛智  谢盛周  吴育波 《华南地质与矿产》2004,(2):40-45

烟塘岩体位于海南岛东部，岩石化学成分上具高Si富K，贫Na，Fe和Mg等特点，属壳源过铝质岩浆成因侵入花岗岩。研究表明，烟塘岩体的源岩主要是海南岛结晶基底抱板群变质火山岩和砂泥质变沉积岩，其形成主要与岩石圈汇聚、挤压碰撞、陆壳加厚有关，可能是古特提斯洋闭合、琼北与琼中两大地块之间“挤压-碰撞-陆壳加厚”这一深部构造作用的浅部响应。  相似文献   

Longwave Measurements for the Coast of British Columbia and Improvements to the Tsunami Warning Capability   总被引：1，自引：0，他引：1  

Rabinovich  Alexander B.  Stephenson  Fred E. 《Natural Hazards》2004,32(3):313-343

A few years ago the Canadian Hydrographic Service initiated a major upgrade toall tide gauges and tsunami stations on the coast of British Columbia (B.C.). Thisprogram was undertaken to address shortcomings of the earlier digital systems andwas driven by concerns about emergency response continuity in the year 2000. By1999, thirteen tide gauge stations had been installed and were operational. Three ofthese stations (Tofino, Winter Harbour, and Langara) were selected for use as tsunamiwarning stations. Several years of continuous, high quality data have now been collectedat these stations and used for analysis of long waves in the tsunami frequency band.Careful examination of these data revealed two weak tsunamis recorded by severalB.C. stations: a distant tsunami of June 23, 2001 generated by the Peru Earthquake(M_w = 8.4), and a local tsunami of October 12, 2001 induced by the Queen Charlotte Earthquake (M_w = 6.3$). Spectral characteristics of these two tsunamis are compared with the spectral characteristics of long waves generated by a strong storm (October, 2000) and of ordinary background oscillations. The topographic admittance functions (frequency responses) constructed for all stations showed that most of them (in particular, Winter Harbour, Tofino, Bamfield, Port Hardy, and Victoria) have strong resonance at periods from 2.5 to 20 min, indicating that these locations are vulnerable to relatively high-frequency tsunamis. The Winter Harbour station also has two strong resonant peaks with periods of 30 and 47 min and with amplification factors of about 7. The estimated source functions show very clear differences between long waves associated with the seismic source (typical periods 10–30 min) and those generated by a storm, which typically have shorter periods and strong energy pumping from high-frequencies due to non-linear interaction of wind waves.  相似文献