华北太古宙长英质岩石的地震波速度及其在地壳中的位置.   总被引：2，自引：1，他引：1       下载免费PDF全文

孙君秀  谢亦汉  张友南 《地震学报》2000,22(6):622-631

研究了两项内容:① 在室温高压和高温高压条件下,华北地区长英质结晶岩的压缩波速度;② 在常压和石英-相变温度下,长英质岩石的加热声发射．结果表明:在相同的温压条件下,长英质结晶岩的波速明显低于基性岩,而与变质相的关系不大;含石英岩石的波速曲线具有与其它任何岩石不同的曲线形态,显示了-相反应峰;在常压下加热岩石至石英相变点时,长英质深变质岩和岩浆花岗岩产生声发射,另一种交代成因的花岗岩不产生声发射．其地质意义表明:结合其它地学资料解释了华北克拉通区的地壳组成,阐明了石英和石英的存在空间;说明了新生代构造沉降区下地壳岩石中石英的-相变以及角闪石和黑云母的脱水熔融是沉降区和隆起区间断裂活动（张性断裂）和地震活动的动力．   相似文献   

浙江中生代火山岩时代厘定和问题讨论：兼评Lapierre等关于浙江中？…   总被引：12，自引：1，他引：11  

陶奎元  邢光福 《地质论评》2000,46(1):14-21

浙江中生代火山岩的时代长期以来存在不同意见,主要分岐为浙江磨石山群和浙西建德群时代窨是晚侏罗世、早白垩世、抑或晚白垩世。Ｌａｐｉｅｒｒｅ等（１９９７）的一文中据两条Ｒｂ－Ｓｒ等时线年龄,给出了如下论断;浙西火山活动（建德群）时代为１２４Ｍａ,划归为第一幕第一次岩浆事件;浙东（磨石山群）时代为９７Ｍａ,划归为第一幕第二次岩浆事件,而第二幕岩浆事件（指永康群）时代〈９７Ｍａ,本文就Ｌａｐｉｅｒｒｅ等文  相似文献   

皖南新元古代井潭组火山岩锆石U-Pb定年和同位素地球化学研究   总被引：10，自引：0，他引：10  

吴荣新  郑永飞  吴元保 《高校地质学报》2007,13(2):282-296

对皖南江南造山带新元古代井潭组火山岩样品进行了锆石微区U-Pb定年、全岩主微量元素分析和Sr-Nd同位素分析以及矿物氧同位素分析。结果表明,井潭组火山岩存在二期火山岩,形成时代分别为820±16 Ma和776±10 Ma。所有样品都具有较高的基性组分(ΣTiO2+ Fe2O3 T+MgO) 含量(4.7%~16.36%),LREE富集,中等Eu负异常,大离子亲石元素K,Rb,Ba,Th,U等富集,Nb,Ta,Sr,Ti等相对亏损。εNd (t )值为-2.79~-1.71,指示岩浆源区含有显著的新生地壳组分。这些岩石具有高A/CNK(1.37~1.61)和高δ18O值(锆石6.52‰~8.98‰),显示为壳源S型岩浆岩的特点。石英、斜长石和钾长石等矿物氧同位素具有很大的变化范围,表明井潭组火山岩经历了不同程度的亚固相中温热液蚀变。根据锆石U-Pb定年和元素以及同位素分析结果,776±10 Ma井潭组火山岩与石耳山花岗岩为同期岩浆岩,井潭组火山岩直接来源于早新元古代新生地壳重熔,而石耳山花岗岩源岩为约825 Ma岩浆岩,间接来源于早新元古代新生地壳的再造。这些新生地壳是江南弧–陆碰撞造山带的组成部分,在Rodinia超大陆裂解时发生拉张跨塌熔融,既不是地幔柱岩浆活动产物,也不是岛弧岩浆作用的直接产物,而是板块–裂谷岩浆活动产物。  相似文献   

Geology and Mineral Chemistry of the Deosai Volcanics, Baltistan, N. Pakistan     

Syed Hamidullah 《地学前缘》2000,(Z1)

GEOLOGY AND MINERAL CHEMISTRY OF THE DEOSAI VOLCANICS, BALTISTAN, N. PAKISTAN  相似文献   

A Mechanism for the Building of the Qinghai-Tibet Plateau     

BAI Wenji  YANG Jingsui  SHI Rendeng 《Continental Dynamics》1999,(2)

l.IntroductionSinceArgand's(l924)recognitionthattheCenozoictectonicsoftheHighAsiaareprincipallytheresultoftheconvergenceofGondwanancontinentalfragmentswithLaurisic,therehasbeenageneralacceptanceoftheviewthattheHimalayasandQinghai-TibetPlateauhavebeenformedbyacollisionbetweentheIndianandTibetcontinentsalongtheIndus-Zangbosuture(MolnarandTapponnief,l975,Sengor,l979;ChenBingwei,l982;DengWanming,l978,HuangJiqing,l954;LoZhongshu,l982;PanGuitangetal.,l984,WangQianshenetal.,l982,Besseetal.…  相似文献   

阿尔泰麦兹地区海相火山岩及其与成矿作用的关系   总被引：2，自引：0，他引：2  

张进红  王京彬  丁汝福 《地质论评》1999,45(7):1116-1125

阿尔泰麦兹地区下泥盆统康布铁堡组火山岩,下亚组为偏碱性的富钠流纹岩夹少量的拉斑—碱性玄武岩和粗安岩;上亚组为钙碱性流纹岩类。其构造环境为大陆边缘活化带。下亚组基性火山岩来源于过渡—富集型地幔,酸性火山岩为壳幔混合源,岩浆经历了结晶分异、岩浆混合和岩浆不混熔作用;上亚组酸性火山岩来源于地壳,岩浆演化主要为与上地壳和海水的同化混染作用。本文还探讨了火山岩与铁和铅锌成矿作用的关系。  相似文献   

Timing of Anatexis within the Berere HTHP Complex Belt of Maevatanana Area, North-Central Madgascar, and its Geological Significance     

LI Peng  LIU Shanbao  LI Jiankang  SHI Guanghai  LIU Xiang 《《地质学报》英文版》2020,94(5):1393-1409

The Berere HTHP Complex belt in Maevatanana area of north–central Madagascar formed in the ~ 2.5 Ga orogeny and underwent high temperature (up to 1050oC) and high pressure (up to 11.5 kbar) granulite facies metamorphism. Then a widespread anatexis took place and numerous widely distributed felsic leucosomes formed. The majority of these leucosomes are parallel to the schistosity of the complex or are present as stockworks, as thin layers, or as lenses at different scales in the host rocks. Here, we report new petrographic data, zircon LA-ICP-MS U-Pb ages, and Lu–Hf isotopic data for felsic leucosomes within this complex. Anatexis, as identified by the petrological study of felsic leucosomes in the field and in thin sections, involved initial ternary feldspar exsolving to produce antiperthite and a quartz + plagioclase ± K-feldspar + sericite mineral assemblage around feldspar grain boundaries. Dissolution is apparent along muscovite grain boundaries, and residual sericite is present around the margins of feldspar and quartz, all suggesting that anatexis was driven by reactions involving muscovite. Zircon U–Pb dating indicates that the felsic leucosomes within the complex formed at 2467–2369 Ma. The majority of samples have positive εHf(t) values, although a few have negative values, suggesting their formation from magmas predominantly sourced from the depleted mantle, possibly with the involvement of minor amounts of crustal materials. Two-stage Hf model ages and εHf(t) values for these samples are consistent with those for gneisses of the basement, indicating that the felsic leucosomes were formed by the anatexis of gneisses and both of their protolith formed during the formation of continental crust in Meso-Neoarchean (ca. 3.1–2.7 Ga). As such, the crystallization age of the felsic leucosome (~2.4 Ga) represents the timing of regional anatexis and a change to post-orogenic tectonism. And this anatexis is also corresponds to the thermal event in Dharwar craton in India which has a pronounced similar Precambrian geology with Madagascar, providing an important constraints on the correlation of the two continental fragments  相似文献   

辽宁永宁地区含金刚石闪长质岩石显微特征及金刚石来源探讨          下载免费PDF全文

杨献忠  王爱国  周延  徐华  徐敏成  杨杰 《地质找矿论丛》2023,38(2):185-196

辽宁永宁地区发育一套闪长质火山岩，该岩石中曾选获金刚石及其指示矿物，因此成为辽宁省金刚石第Ⅳ成矿带。通过对该岩石矿物组成及其显微结构构造特征研究，表明：(1)闪长质岩石中的斑晶斜长石具有环带结构；(2)橄榄石及金云母具有多世代性，且目估橄榄石+金云母含量在10%以上，局部更为富集；(3)出现“橄榄石+金云母+石榴石”与“斜长石+辉石+角闪石”不平衡的矿物组合；(4)发现橄榄石有碎斑结构和金伯利岩角砾。初步认为，永宁地区的闪长质岩浆在上升过程中捕获了早先已形成的金伯利岩并与之发生熔融混合作用，金刚石来自于深部的金伯利岩。这一认识对该地区寻找金刚石原生矿具有启示意义。  相似文献   

The Cretaceous volcanic succession around the Songliao Basin,NE China: relationship between volcanism and sedimentation     

Pujun Wang  Yanguang Ren  Xuanlong Shan  Shaobo Sun  Chuanbiao Wan  Weihua Bian 《Geological Journal》2002,37(2):97-115

With volume ratio of 8:1:1.5 amongst acidic, intermediate and basaltic rocks, the Cretaceous volcanics around the Songliao Basin are a series of high‐K or medium‐K, peraluminous or metaluminous, calc‐alkaline rocks, lacking typical basalts and peralkaline members of typical rift‐related types. Their eruption ages range between 133 and 127 Ma, 124 and 122 Ma and 117 and 113 Ma respectively. They are high in total (Rare earth element) REE contents (96.1–326 ppm), enriched in LREE and depleted in HREE (LREE/HREE = 4.6–13.8), with negative Eu and Ce anomalies (Eu/Eu* = 0.04–0.88; Ce/Ce* = 0.60–0.97). They have enriched large‐ion lithophile elements (e.g. K, Ba, Th) and depleted high field strength elements (e.g. Nb, Ti and Y), suggesting a subduction‐related tectonic setting. The volcanic activities migrated from south to north, forming a successively northward‐stepping volcanic series and showing a feature significantly different from the overlying sedimentary sequence striking northeast. Thus, an overlap basin model was proposed. Accompanied by opening of the basin, the volcanogenic succession was formed at the block‐faulting stage (131–113 Ma) owing to the closure of the Mongolia–Okhotsk ocean in the Jurassic and early Cretaceous, while the overlying sedimentary sequence was unconformably deposited at the spreading stage (Albian–Maastrichtian) owing to the oblique subduction of the Pacific plate under the Eurasian plate. The volcanic succession constitutes the lower unit of basin filling and is the forerunner of further basin spreading. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献