山东临朐山旺新生代玄武岩中超镁铁岩包体的研究   总被引：5，自引：0，他引：5  

王方正  金隆裕  徐耀荣 《地球科学》1987,(3)

山旺新生代玄武岩中的超镁铁质包体分为五类:尖晶石纯橄榄岩、尖晶石二辉橄榄岩、尖晶石方辉橄榄岩、尖晶石石榴石二辉岩和石榴石二辉橄榄岩。对它们的地质学,岩相学、岩石化学,造岩矿物的化学成分,稀土配分模式及热力学计算的研究表明,前三种岩石属原始地幔岩,后二种是地幔中岩浆作用的产物。  相似文献   

我国东部若干地区新生代玄武岩中长石巨晶的特征及成因   总被引：2，自引：0，他引：2  

邱家骧  刘蒙华 《矿物学报》1987,(1)

本文汇集了中国东部新生代玄武岩中76个长石巨晶的化学成分,并与53个国外长石巨品进行了对比。文中对长石巨晶的产状、物理性质、矿物化学及微量元素进行了研究,并对国际上关于长石巨晶五个有争议的问题进行了讨论。作者同时也提出了自己的观点。  相似文献   

阿尔泰东部新生代火山岩的地球化学特点及构造环境   总被引：3，自引：0，他引：3  

王登红  李天德 《大地构造与成矿学》2001,25(3):282-289

新疆三大山系均有新生代火山岩,其中南部西昆仑、阿尔金山及天山托云等地的新生代火山岩比较发育,在新疆东北部地区的阿尔泰哈拉乔拉一带也发育新生代的陆内喷发火山岩。这套火山岩虽然面积不是很大,但具有大陆溢流玄武岩的特点。在地球化学上也具有典型热点成因洋岛玄武岩或其它地幔柱成因玄武岩的特点,如TiO2含量高大于2%、轻稀土元素和不相容元素显著富集等。表明新疆北部特别是阿尔泰造山带东部演化到新生代以后,有向裂陷拉张方向演化的趋势,标志着一个新的大地构造演化阶段的到来。  相似文献   

威宁铜厂河玄武岩铜矿成矿地质特征及成因探讨   总被引：3，自引：0，他引：3  

武国辉  金中国  董家龙 《矿产与地质》2005,19(5):482-486

研究威宁铜厂河铜矿区玄武岩的岩石类型、常量元素、微量元素及稀土元素地球化学特征,探讨玄武岩铜矿的成矿地质背景、控矿因素、产出特征和成矿规律,系统总结了找矿标志.研究认为,本区玄武岩具大陆拉斑玄武岩特征,铜矿属火山同生热液成矿叠加埋藏变质作用改造形成的玄武岩铜矿.  相似文献   

Triassic mid-oceanic sedimentation in Panthalassa Ocean: Sambosan accretionary complex, Japan     

Tetsuji  Onoue  Hiroyoshi  Sano 《Island Arc》2007,16(1):173-190

Abstract   The Sambosan accretionary complex of southwest Japan was formed during the uppermost Jurassic to lowermost Cretaceous and consists of basaltic rocks, carbonates and siliceous rocks. The Sambosan oceanic rocks were grouped into four stratigraphic successions: (i) Middle Upper Triassic basaltic rock; (ii) Upper Triassic shallow-water limestone; (iii) limestone breccia; and (iv) Middle Middle Triassic to lower Upper Jurassic siliceous rock successions. The basaltic rocks have a geochemical affinity with oceanic island basalt of a normal hotspot origin. The shallow-water limestone, limestone breccia, and siliceous rock successions are interpreted to be sediments on the seamount-top, upper seamount-flank and surrounding ocean floor, respectively. Deposition of the radiolarian chert of the siliceous rock succession took place on the ocean floor in Late Anisian and continued until Middle Jurassic. Oceanic island basalt was erupted to form a seamount by an intraplate volcanism in Late Carnian. Late Triassic shallow-water carbonate sedimentation occurred at the top of this seamount. Accumulation of the radiolarian chert was temporally replaced by Late Carnian to Early Norian deep-water pelagic carbonate sedimentation. Biotic association and lithologic properties of the pelagic carbonates suggest that an enormous production and accumulation of calcareous planktonic biotas occurred in an open-ocean realm of the Panthalassa Ocean in Late Carnian through Early Norian. Upper Norian ribbon chert of the siliceous rock succession contains thin beds of limestone breccia displaced from the shallow-water buildup resting upon the seamount. The shallow-water limestone and siliceous rock successions are nearly coeval with one another and are laterally linked by displaced carbonates in the siliceous rock succession.  相似文献   

Geochemistry of the high-Mg andesites at Zhangwu, western Liaoning: Implication for delamination of newly formed lower crust   总被引：6，自引：0，他引：6  

Huang Hua  Gao Shan  Hu ZhaoChu  Liu XiaoMing  Yuan HongLing 《中国科学D辑(英文版)》2007,50(12):1773-1786

Ten volcanic samples at Zhangwu,western Liaoning Province,North China were selected for a sys-tematic geochemical,mineralogical and geochronological study,which provides an opportunity to ex-plore the interaction between the continental crust and mantle beneath the north margin of the North China craton.Except one basalt sample(SiO2= 50.23%),the other nine samples are andesitic with SiO2 contents ranging from 53% to 59%.They have relatively high MgO(3.4%―6.1%,Mg#=50―64) and Ni and Cr contents(Ni 27×10?6―197×10?6,Cr 51×10?6―478×10?6).Other geochemical characteristics of Zhangwu high-Mg andesites(HMAs) include strong fractionation of light rare earth elements(LREE) from heavy rare earth elements(HREE),and Sr from Y,with La/Yb greater than 15,and high Sr/Y(34― 115).Zircons of andesite YX270 yield three age groups with no Precambrian age,which precludes ori-gin of the Zhangwu HMAs from the partial melting of the Precambrian crust.The oldest age group peaking at 253 Ma is interpreted to represent the collision of the Siberia block and the North China block,resulting in formation of the Central Asian orogenic belt by closure of the Mongol-Okhotsk Ocean.The intermediate age group corresponds to the basalt underplating which caused the wide-spread coeval granitoids in the North China craton with a peak 206Pb/238U age of 172 Ma.The youngest age group gives a 206Pb/238U age of 126±2 Ma,which is interpreted as the eruption age of the Zhangwu HMAs.The high 87Sr/86Sri(126 Ma)>0.706 and low εNd(t)= ?6.36―?13.99 of the Zhangwu HMAs are distinct from slab melts.The common presence of reversely zoned clinopyroxene phenocrysts in the Zhangwu HMAs argues against the origin of the Zhangwu HMAs either from melting of the water saturated mantle or melting of the lower crust.In light of the evidence mentioned above,the envisaged scenario for the formation of the Zhangwu HMAs is related to the basaltic underplating at the base of the crust,which led to the thickening of the lower crust and formation of lower crustal eclogite,followed by foundering of the eclogitic lower crust into the asthenosphere.The foundered eclogite then melted and the resul-tant melts interacted with surrounding peridotite during their upward transport,which finally produced the high-Mg andesites.This well explains the high-Mg adakitic characters and absence of ancient in-herited zircon in the Zhangwu lavas.  相似文献   

准噶尔盆地陆梁地区基底火山岩的岩石地球化学及其构造环境   总被引：16，自引：9，他引：16  

王方正  杨梅珍等 《岩石学报》2002,18(1):9-16

准噶尔盆地腹地陆梁起基底火山岩岩性为富钠玄武岩及流纹岩，总体显示出板内双峰火山岩特点。玄武岩的特征是：岩石的五晶和基质中普遍出现橄榄石；辉石为普通辉石；斑晶和基质中的长石为偏酸性的斜长石（平均牌号为30－50）；全岩化学成分CIPW计算结果表明，绝大部分含有Ne（2．8％－4．6％），均含有O1（19．3％－10．1％）和Di（0．2％－24．6％），标准矿物分子组合为Ne＋O1＋Di＋An；在全碱－SiO2图上玄武岩投影于碱性区；Mg^#＜65；REE总量为110．29－158．06μg/g。（La/Y）N变化范围为3．10－4．51。δEu变化于0．93－1．04；弱武岩的微量元素标准化图解为LILE相对于LREE适度富集，Nb,Ta相对于LREE和LILE亏损。Ni,Cr含量略低于原始岩浆的参考值；以上特征表明，弱武岩总体上属于碱性橄榄玄武岩；玄武岩具有较同正的εNd(t)和低的^87Sr/^86Sr，而流纹岩则具有较低的εNd(t)和较高的^87Sr/^86Sr，反映它们的同源性和遭受陆壳物质同化混染程度的不同。同位素Rb-Sr等时线年龄和单颗粒锆石蒸发年龄集中在323－395Ma。以上特点表明，陆梁玄武岩来自于亏损的地幔源区，并经历了一定程度的分异作用和陆壳物质的混染作用，其形成于板内环境，与泥盆纪－石灰纪区域伸展作用有关，因此，陆梁隆起带基底很可能是一个大陆裂谷带。  相似文献   

海底玄武岩中的中酸性玻璃质熔体研究     

陈小明  赵广涛  李巍然  潘燕宁 《地学前缘》2001,8(3):216-222

笔者在冲绳海槽海底玄武岩基质中发现的中酸性玻璃质熔体 ,与以往在基性火山岩中发现的玻璃质熔体存在明显的差异 :( 1)在存在状态上 ,前者呈充填状态存在于细小的基质矿物之间 ,其体积明显受到岩浆冷却速率的制约 ;后者常出现富铁相和富硅相两种熔体共存现象 ,且一种熔体常呈球状分布于另一种熔体中。 ( 2 )在成分演化上 ,前者随着冷却速率的降低 ,成分向酸性方向演化 ;后者的成分与冷却速率间的关系不明显 ,一直表现为富铁相和富硅相两端员成分 ,缺失中间过渡成分。这两种类型的熔体 ,分别反映了幔源岩浆不同的演化过程 :冲绳海槽海底玄武岩中的中酸性玻璃质熔体 ,反映了幔源岩浆结晶分异演化过程 ,并记录了演化过程中各阶段产物的特征 ;而以往在基性火山岩中发现的富铁相和富硅相两种熔体的共存现象 ,反映了幔源岩浆的熔离过程 ,并记录了熔离产物的特征。  相似文献   

桐庐杂岩体中共存的两种碱性长石研究          下载免费PDF全文

陈小明  刘昌实等 《地质论评》2001,47(3):317-321

桐庐同熔型火山－侵入杂岩中出现两种碱性长石，一种为无色透明，另一种为微红色，本文利用X射线衍射仪，电子探针，透射电镜对其结构态，成分及出溶微结构进行了对比研究。结果表明，两者成分差别不大，而结构差别较大，无色透明的为透长石，出溶叶片发育；微红色的为正长石或低透长石，出溶结构不发育。而且随着冷却速率的变慢，无色透明碱性长石的Al/Si有序度增大，微红色碱性长石的有序度降低，分析后认为这种共存现象是岩浆混和造成的，从而为桐庐杂岩体的岩浆混合成因提供了有力的证据。  相似文献   

Geochemical Characteristics and Genesis of Late Cretaceous to Paleogene Basalts in the Tuyon Basin, South Tianshan Mountains     

WANG Yanbin  WANG Yong  LIU Xun  FU Derong  XIAO Xuchang  QI Longshui . Institute of Geology  Chinese Academy of Geological Sciences  Beijing . Hebei College of Technology  Tangshan 《Continental Dynamics》2001,(1)

1. Introduction The Tianshan Mountains is a typical intercontinental orogenic belt in the world. From late Carboniferous to Permian, the old Tianshan formed during the tectonic amalgamation of the Tarim block, Tianshan block and Siberia craton (Carroll et al, 1990). Mid-Cenozoic basalts are widely distributed in both the Tuyon basin of southwest Tianshan and its western part of Tianshan in Jierjisi in late Cretaceous-Paleogene period, which indicates the activation of the old Tianshan.…  相似文献