博格达山东段石炭纪火山岩地球化学及构造属性   总被引：1，自引：0，他引：1  

梁婷  郭新成  高景刚  范廷宾  秦海峰  周汝洪  黑欢 《新疆地质》2011,29(3):289-295

博格达东段石炭系火山岩发育,通过1:5万区域地质调查工作,将该区划分为3个组,即下石炭统七角井组、上石炭统下部柳树沟组及上石炭统中上部祁家沟组.文中对3组地层中火山岩地质及岩石学、主量元素、稀土元素、微量元素地球化学特征研究表明,下石炭统七角井组、上石炭统下部柳树沟组是以拉斑玄武岩为主的双峰式火山岩建造,上石炭统中上部祁家沟组是小范围火山岩-碎屑岩-碳酸盐岩建造,各组火山岩均为钙碱性拉斑系列,岩浆源是幔源岩浆与地壳物质混合物,形成环境为板内裂谷环境.  相似文献   

长江中下游地区蝌蚪山早白垩世玄武岩中单斜辉石的矿物学研究及其地质意义     

文施华  侯通 《矿物岩石》2011,31(3)

长江中下游地区繁昌火山盆地在早白垩世先后发育3个喷发旋回:中分村旋回、赤沙旋回和蝌蚪山旋回。其中蝌蚪山旋回下段以凝灰质粉砂岩为主,中段为玄武岩和流纹质凝灰岩互层,上段以流纹岩为主。蝌蚪山玄武岩中的辉石既存在斑晶中也存在于基质中,这两种辉石在成分上有明显的差异,从斑晶辉石的核部到边部再到基质的核部,化学成分由富镁向富铁演化,显示出拉斑玄武岩系列的特点,辉石成因的判别图解表明其寄主岩浆为板内拉斑玄武岩,但其化学成分的变化趋势又表明岩浆在结晶分异的过程中向着碱性系列演化。根据单斜辉石与熔体平衡原理计算出玄武岩形成时的温度约为1 100℃,压力约为400MPa,相应的深度约为15km,证明岩浆在地壳中有过短暂的停留,并在上地壳部位发生分离结晶作用后喷出地表快速冷凝形成蝌蚪山玄武岩。  相似文献   

内蒙古贝力克玄武岩地球化学特征及地质意义   总被引：5，自引：2，他引：3  

陈生生  樊祺诚  赵勇伟  史仁灯 《岩石学报》2013,29(8):2695-2708

内蒙贝力克地区存在一片面积为400km2、以发育三级熔岩台地为特征的新生代玄武岩,台地时代分别为2.31 ～2.41Ma、1.56～1.61Ma、0.51～0.61Ma.岩性为具有过渡性质的拉斑玄武岩,分为石英拉斑玄武岩与橄榄拉斑玄武岩,它们都起源于具有交代性质的石榴石橄榄岩源区.地球化学特征显示这两种岩性之间没有演化关系,而是源区不同程度、深度部分熔融的结果;并且在上升过程中,都受到下地壳麻粒岩的混染作用,其中石英拉斑玄武岩混染程度最大.大地构造背景上,贝力克与赤峰同处在兴蒙造山带南缘,它们表现出与华北西部北缘(集宁、大同、汉诺坝、繁峙)相似的岩浆源区和岩石圈地幔热状态,但不同的富集岩石圈地幔类型,即兴蒙造山带南源呈现DMM-EMⅡ特点,而华北西部北缘具有DMM-EM Ⅰ混合趋势.这种差异可能与岩石圈地幔不同的时代及构造背景有关.在软流圈熔体与上覆岩石圈地幔相互反应的拉斑玄武岩成因模式基础上,认为华北岩石圈减薄现象不仅局限于克拉通内部,其处在克拉通西北部,乃至兴蒙造山带南缘也同样经历了岩石圈减薄过程,只是存在不同时间、程度的岩石圈减薄过程.  相似文献   

Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group,the Ogasawara Islands     

Kyoko Kanayama  Susumu Umino  Osamu Ishizuka 《Island Arc》2012,21(4):288-316

The Ogasawara Islands mainly comprise Eocene volcanic strata formed when the Izu–Ogasawara–Mariana Arc began. We present the first detailed volcanic geology, petrography and geochemistry of the Mukojima Island Group, northernmost of the Ogasawara Islands, and show that the volcanic stratigraphy consists of arc tholeiitic rocks, ultra‐depleted boninite‐series rocks, and less‐depleted boninitic andesites, which are correlatable to the Maruberiwan, Asahiyama and Mikazukiyama Formations on the Chichijima Island Group to the south. On Chichijima, a short hiatus is identified between the Maruberiwan (boninite, bronzite andesite, and dacite) and Asahiyama Formation (quartz dacite and rhyolite). In contrast, these lithologies are interbedded on Nakodojima of the Mukojima Island Group. The stratigraphically lower portion of Mukojima is mainly composed of pillow lava, which is overlain by reworked volcaniclastic rocks in the middle, whereas the upper portion is dominated by pyroclastic rocks. This suggests that volcanic activity now preserved in the Mukojima Island Group records growth of one or more volcanoes, beginning with quiet extrusion of lava under relatively deep water followed by volcaniclastic deposition. These then changed into moderately explosive eruptions that took place in shallow water or above sea level. This is consistent with the uplift of the entire Ogasawara Ridge during the Eocene. Boninites from the Mukojima Island Group are divided into three types on the basis of geochemistry. Type 1 boninites have high SiO₂ (>57.0 wt.%) and Zr/Ti (>0.022) and are the most abundant type in both Mukojima and Chichijima Island Groups. Type 2 boninites have low SiO₂ (<57.1 wt.%) and Zr/Ti (<0.014). Type 3 boninites have 57.6–60.7 wt.% SiO₂ and are characterized by high CaO/Al₂O₃ (0.9–1.1). Both type 2 and 3 boninites are common on Mukojima but are rare in the Chichijima Island Group.  相似文献   

Cambrian–early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: Continental break-up and rifting of the northern Gondwana margin     

André Pouclet  J. Javier Álvaro  Jacques-Marie Bardintzeff  Andrés Gil Imaz  Eric Monceret  Daniel Vizcaïno 《地学前缘(英文版)》2017,8(1):25-64

The Cambrian–lower Ordovician volcanic units of the South Armorican and Occitan domains are analysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Cambrian–Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases: (1) basal Cambrian rhyolites, (2) upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, (3) upper lower–middle Cambrian continental tholeiites, (4) Tremadocian rhyolites, and (5) upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic continental rift is termed the “Tremadocian Tectonic Belt” underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that forecasted the South Armorican–Medio-European Ocean as a part of the Palaeotethys Ocean.  相似文献   

柴达木盆地周边火山岩产出地质特征和含矿性     

姜福芝  王玉往 《地质论评》1999,45(7):1019-1027

柴达木盆地周边火山岩十分发育,形成巨大的环状火山岩带。本文着重于研究火山岩的时空分布、产出古地理环境、以及它们的岩石学和岩石化学,以指出其产出构造环境和演化地质历史。根据火山成矿作用与铜多金属等矿产的密切关系和该区火山岩含矿特征,探讨了其含矿可能性。  相似文献   

南天山榆树沟遭受麻粒岩相变质改造的蛇绿岩套研究   总被引：10，自引：1，他引：9       下载免费PDF全文

王润三  王居里  周鼎武  王焰  刘养杰 《地质科学》1999,(2):166

 新疆南天山榆树沟高压麻粒岩地体的原岩是一层序基本完整的蛇绿岩套。该岩套主要由变质橄榄岩、超镁铁质-镁铁质堆晶岩、下部洋脊拉斑玄武岩、以及上部洋脊拉斑玄武岩等四个岩石单元构成。其岩石学和REE与相对惰性微量元素的地球化学特征表明,该蛇绿岩中的玄武岩属洋脊型;结合区域地质背景分析,初步认为榆树沟蛇绿岩可能形成于具相当规模的洋盆构造环境。锆石U-Pb年龄表明其形成时代为早古生代中晚期,证实西南天山早古生代蛇绿岩确已延伸至库米什一带。榆树沟麻粒岩相蛇绿岩套的确定以及对其独特的形成和俯冲-折返过程进行深入研究,不仅对进一步探讨天山构造带的形成和演化有重要意义,而且对发展大陆动力学理论也具重要参考价值。  相似文献   

Evolution of the Bhandara-Balaghat granulite belt along the southern margin of the Sausar Mobile Belt of central India     

H. M. Ramachandra  Abhinaba Roy 《Journal of Earth System Science》2001,110(4):351-368

The Bhandara-Balaghat granulite (BBG) belt occurs as a 190 km long, detached narrow, linear, NE-SW to ENE-WSW trending belt that is in tectonic contact on its northern margin with the Sausar Group of rocks and is bordered by the Sakoli fold belt in the south. The Bhandara part of the BBG belt is quite restricted, comprising a medium to coarse grained two-pyroxene granulite body that is of gabbroic composition and preserves relic igneous fabric. The main part of the belt in Arjuni-Balaghat section includes metasedimentary (quartzite, BIF, Al- and Mg-Al metapelites) and metaigneous (metaultramafic, amphibolite and two-pyroxene granulite) protoliths interbanded with charnockite and charnockitic gneiss. These rocks, occurring as small bands and enclaves within migmatitic and granitic gneisses, show polyphase deformation and metamorphism. Geochemically, basic compositions show tholeiitic trend without Fe-enrichment, non-komatitic nature, continental affinity and show evolved nature. Mineral parageneses and reaction textures in different rock compositions indicate early prograde, dehydration melt forming reactions followed by orthopyroxene stability with or without melt. Coronitic and symplectitic garnets have formed over earlier minerals indicating onset of retrograde IBC path. Evidences for high temperature ductile shearing are preserved at places. Retrogressive hydration events clearly post-date the above paths. The present study has shown that the BBG belt may form a part of the Bastar Craton and does not represent exhumed oceanic crust of the Bundelkhand Craton. It is further shown that rocks of the BBG belt have undergone an earlier high-grade granulite metamorphism at 2672 ± 54 Ma (Sm-Nd age) and a post-peak granulite metamorphism at 1416 ± 59Ma (Sm-Nd age, 1380 ± 28Ma Rb-Sr age). These events were followed by deposition of the Sausar supracrustals and Neoproterozoic Sausar orogeny between 973 ± 63Ma and 800 ± 16Ma (Rb-Sr ages).  相似文献   

江山-广丰地区早白垩世晚期玄武岩的岩石地球化学及其构造意义   总被引：17，自引：0，他引：17  

余心起  舒良树  颜铁增  俞云文  祖辅平  王彬 《地球化学》2004,33(5):465-476

江山-广丰地区所在的信江红色盆地与金衢红色盆地同属于NEE向赣杭断陷盆地带的组成部分.赣杭构造带自早白垩世晚期开始强烈拉张,红色盆地形成.红层下部夹有层状玄武岩,全岩K-Ar年龄为98～105 Ma,属早白垩世晚期.岩石地球化学特征表明研究区有两类玄武岩:江山陈塘坞一带的拉斑玄武岩,礼贤、广丰一带的碱性橄榄玄武岩.Nd、Sr同位素组成分析显示,拉斑玄武岩类(87Sr/86Sr)i值为0.705 4～0.707 0,εNd(t)值为1.69～0.70(接近于0),表明源区为基本未受壳源物质混染的原始地幔,在弧后陆缘环境下快速拉张而上升,呈熔岩被形式分布于信江盆地东部;碱性橄榄玄武岩(87Sr/86Sr)i值为0.707 6～0.708 0,而εNd(t)值偏低(-6.43～-5.18),表明来源于已受壳源物质混染的富集地幔,在拉张加剧、裂陷加深的构造背景下喷发,相对集中分布于盆地中部,范围小于拉斑玄武岩.二者的差别主要是地幔源区受到不均匀混染所致.研究表明,早白垩世晚期至晚白垩世期间,太平洋板块俯冲的角度由缓变陡以及向东南方向的后退作用,对弧后陆缘的快速拉张并形成赣杭带红色断陷盆地及其玄武岩起着关键性作用.  相似文献   

北秦岭柞水——太白区段两类激动陆缘型幔源岩浆活动与岩浆过程          下载免费PDF全文

姜常义  苏生瑞  任名华  杨志华 《岩石矿物学杂志》1997,16(4):314-323

研究区内有两类密切共生的活动陆缘型幔源侵入岩组合，它们分属拉斑系列和钙碱系列。这两个系列的侵入岩存在系统的化学差异，而且在高位岩浆房中普遍经历了镁铁矿物的分离结晶作用。  相似文献