Spectral characteristics of the Gawler Range Volcanics in drill core Myall Creek RC1     

G. Gordon  S. McAvaney  C. Wade 《Australian Journal of Earth Sciences》2016,63(8):973-986

Traditional core-logging methods in conjunction with spectral scanning techniques have been used to log volcanic successions of the lower Gawler Range Volcanics. The open-file drill core Myall Creek RC 1 was re-logged and scanned using HyLogger? core scanning technologies as a part of the Geological Survey of South Australia's Southern Gawler Rangers mapping program and the Mineral System Drilling Program. Myall Creek RC 1 is one of the key stratigraphic drill cores for the region, owing to the intersection of a large section of the Gawler Range Volcanics. Spectral characterisation of the Eucarro Rhyolite revealed differential weathering of plagioclase phenocrysts, while high-resolution imagery and spectral results were used to log new basaltic flows and small flow features in the Roopena Basalt. The composition and distribution of feldspars in the unnamed lower Gawler Range Volcanic units were used to aid traditional logging of visually similar lithologies. A spectral scalar, the felsic–mafic index, was used to identify unusual features in the unnamed sequence and was found to identify iron oxides as either fracture coatings or finely disseminated in the matrix of the sample. Iron oxides were also used to identify features within lithological units, which were difficult to discern visually, especially the layers in the deepest layered ignimbrite at the end of the drill core.  相似文献   

松潘-甘孜褶皱带复理石火山岩夹层时代及其地质意义     

李祥辉  王成善  刘树根  冉波  徐文礼  周勇 《地质通报》2016,35(6):879-886

在四川北部松潘西北和甘肃南部合作市一带的上三叠统(深海沉积)复理石中发现了数套火山(碎屑)岩夹层。利用UPb同位素测年,获得4件安山岩、凝灰岩样品锆石的年龄加权平均值分别为205.9±1.6Ma、208.9±1.8Ma、210.4±1.6Ma和212.3±1.5Ma,时代属于晚三叠世诺利期晚期—瑞提期早期。此系第一次较为精准地报道松潘-甘孜褶皱带晚三叠世复理石火山岩夹层及其可能代表的火山喷发年龄。研究结果表明,直到瑞提期早期松潘-甘孜古残留海盆还未停止接受沉积物供给。该套火山(碎屑)岩的测年结果为松潘-甘孜褶皱带上三叠统复理石岩石地层单元的划分和对比提供了重要参考,同时为进一步约束华南与华北板块碰撞-造山事件时限提供了新证据。  相似文献   

新疆东准噶尔卡拉麦里蛇绿岩的形成和侵位时限——来自辉绿岩和凝灰岩LA-ICP-MS锆石U-Pb年龄的证据   总被引：12，自引：3，他引：9  

黄岗  牛广智  王新录  郭俊  宇峰 《地质通报》2012,31(8):1267-1278

新疆东准噶尔卡拉麦里蛇绿岩是中亚造山带中最具代表性的蛇绿岩之一,其所代表的古洋盆的形成和关闭时限一直受到地学界的密切关注。采用LA-ICP-MS锆石U-Th-Pb同位素方法,获得卡拉麦里蛇绿岩中辉绿岩的年龄为416.7Ma±3.2Ma,代表了卡拉麦里蛇绿岩的形成年龄。不整合于蛇绿岩之上的地层凝灰岩的年龄为343.0Ma±5.0Ma,限定了卡拉麦里蛇绿岩侵位时代的上限,同时也为沉积盖层提供了可靠的年龄依据。即卡拉麦里蛇绿岩所代表的古大洋形成于早泥盆世洛霍考夫期,闭合于早石炭世杜内期前。卡拉麦里蛇绿岩形成和侵位时代的准确限定对研究东准噶尔的构造演化和古生代中亚地区构造格局提供了重要的制约。  相似文献   

冀北承德盆地侏罗系九龙山组凝灰岩LA-ICP-MS锆石U-Pb年龄与地球化学特征   总被引：2，自引：1，他引：1  

陈海燕  张运强  张计东  范永贵  彭芊芃  连青  孙立萍  于龙 《地质通报》2014,33(7):966-973

对冀北承德盆地中生代侏罗纪各地层单位的时代归属一直存在争议。研究获得承德盆地九龙山组凝灰岩LA-ICP-MS锆石206Pb/238U年龄加权平均值为163.4Ma±1.1Ma(MSWD=3.3),结合研究区中生代侏罗纪其他地层测年结果,认为九龙山组的时限可能为158~164Ma,属中侏罗世晚期—晚侏罗世早期,对应于国际地层表的牛津期—卡洛维期。该组中的凝灰岩具有较高的SiO2、K2O和Al2O3含量,A/CNK=6.31~16.22,反应岩石高钾偏碱性强过铝质的特点;稀土元素总量高,REE配分曲线呈右倾型,具有明显的Eu和Sr负异常;富集大离子亲石元素(Rb、Ba、Th、U),亏损高场强元素(Nb、Ta、Zr)。凝灰岩具有与上地壳相似的稀土和微量元素特征,具典型的壳源成因类型。  相似文献   

湖南桃源理公港地区含金刚石沉凝灰岩的发现及其找矿意义          下载免费PDF全文

杨献忠  蔡逸涛  康丛轩  黄光昭  李帅  向华 《中国地质调查》2014,6(6):56-62

湖南桃源理公港地区白垩纪红盆内的灰绿色和紫红色沉积夹层曾选获过金刚石。以灰绿色岩石为研究对象,通过薄片鉴定和电子探针分析来确定岩石名称和岩石中石榴石和云母的属性。显微镜下,灰绿色岩石呈凝灰结构,由约45%的晶屑、35%的岩屑和20%的玻屑组成,为较典型的沉凝灰岩,并非前人所述的金伯利岩。沉凝灰岩中的石榴石和云母分别为G10型镁铝榴石和金云母,镁铝榴石和金云母的成分与辽宁、山东及南非典型岩管含金刚石金伯利岩中的镁铝榴石及金云母的成分基本一致,暗示其来源于含金刚石的金伯利岩。沉凝灰岩的特征表明,其来源地不会太远,这为在附近找寻火山机构奠定了基础; 金伯利质岩屑、G10型镁铝榴石和金云母的发现,为在周边寻找原生金伯利岩提供了重要信息。  相似文献   

北秦岭罗汉寺岩群锆石SHRIMP U-Pb年龄及其构造地质意义   总被引：1，自引：0，他引：1  

崔建堂  韩芳林  张拴厚  王根宝  王北颖  王学平  郭岐明  彭海练  王金安  彭俊英  卢婷  付垒  崔海曼 《西北地质》2011,(4):8-14

对出露于北秦岭周至黑河小王涧黄草坪南罗汉寺岩群(弧前盆地沉积楔形体)中的英安质晶屑凝灰岩,进行了锆石SHRIMP U-Pb同位素测年研究,获得该群晶屑凝灰岩形成时代为(491±5)Ma,反映该岩群跨及早奥陶世.结合商丹带北侧广泛发育的加里东期岛弧花岗岩带和前人在其他地区测定该岩群的最新年代信息,认为本次测年数据为北秦岭...  相似文献   

The Hianana Volcanics: Remnants of a Late Permian tuff ring and lava flow,Coombadjha Volcanic Complex,northeastern New South Wales     

J. McPhie 《Australian Journal of Earth Sciences》2013,60(4):417-433

The Hianana Volcanics consist of bedded tuff and dacitic lava that form a locally mappable unit within the extensive, Late Permian silicic volcanic sequence of northeastern New South Wales. Principal components of the bedded tuff are crystal and volcanic lithic fragments ranging from coarse ash to lapilli, accompanied by variable amounts of fine ash matrix. Well denned plane parallel thin bedding is characteristic. Sandwave bed forms, including low‐angle cross‐beds and wavy beds, are confined to an area of 2–3 km² coinciding with the thickest sections (70 m) of bedded tuff. A high‐aspect ratio flow of porphyritic dacitic lava overlies the bedded tuff in the same area. The setting, lithofacies, extent and geometry of the bedded tuffs of the Hianana Volcanics are comparable with modern tuff rings which are composed of the deposits from base surges generated by explosive phreatomagmatic eruptions at primary volcanic vents. Many of these have also discharged lava late in their activity. Proximal parts of the Hianana tuff ring were buried by the porphyritic lava after the phreatomagmatic eruptions had ceased. In more distal sections, the bedded tuff is less than 10 m thick and dominantly comprises fine grained, plane parallel, very thin beds and laminae; these features suggest an origin by fallout from ash clouds that accompanied the phreatomagmatic eruptions. The distal ash was covered and preserved from erosion by a layer of welded ignimbrite, the source of which is unknown.  相似文献   

扬子西缘元古宙峨边群烂包坪组地层归属及其锆石SHRIMP U-Pb年代学证据     

熊国庆  江新胜  崔晓庄  卓皆文  陆俊泽  刘建辉  汪正江  王剑 《地学前缘》2013,20(4):350-360

扬子西缘峨边群地层序列一直以来存在争议,其时代归属缺乏地质年代学约束。通过对扬子西缘元古宙峨边群各组、段岩石组合特征、沉积充填序列及其沉积接触关系的综合分析,初步确定了峨边群烂包坪组地层归属。该地层应位于原峨边群上部,代表一次新的构造旋回开始,已不属于峨边群地层范畴。在烂包坪组下部凝灰岩中首次获得的(779.3±15.7) Ma锆石SHRIMP U Pb年龄,进一步证实其形成于新元古代,而非中元古代。(2 737±30) Ma和(2 480±29) Ma的两个单颗粒锆石SHRIMP U Pb年龄,表明扬子西缘峨边-金口河地区可能存在古老的新太古代结晶基底。这些研究成果和新的认识将有助于推动扬子西缘峨边群研究工作的深入开展。  相似文献   

苏门答腊外海13.5万年来的火山灰记录:来自深海沉积物岩心IR-GC1的证据     

QIU Zhongyan  HAN Xiqiu  JIN Xianglong  WANG Yejian  ZHU Jihao 《海洋学报(英文版)》2014,33(12):75-80

Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with the δ18O-based age, it is suggested that ash Layer A is correlated to the youngest Toba tuff(YTT), Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic eruption event.  相似文献   

扬子克拉通北缘大洪山地区打鼓石群与神农架地区神农架群的对比:锆石SHRIMP U-Pb年龄及Hf同位素证据     

李怀坤  田辉  周红英  张健  刘欢  耿建珍  叶丽娟  相振群  瞿乐生 《地学前缘》2016,23(6):186-201

出露于扬子克拉通北缘大洪山地区的打鼓石群一直被认为是一套中元古代沉积地层,其上被花山群不整合覆盖。但是由于缺少可靠的年龄依据,打鼓石群与同属扬子克拉通北缘的神农架群以及其他相关地层的对比关系一直存有争议。本文作者利用高精度高分辨率离子探针质谱仪(SHRIMP)测定了打鼓石群中凝灰岩的锆石U-Pb年龄,并利用激光烧蚀多接收器电感耦合等离子体质谱仪(LA-MC-ICPMS)测定了打鼓石群凝灰岩和基本同时代的神农架地区神农架群上亚群凝灰岩的锆石Lu-Hf同位素。这是迄今为止第一次测得了打鼓石群罗汉岭组凝灰岩年龄(1 225±19) Ma和(1 239±23) Ma;锆石Lu-Hf同位素结果显示打鼓石群罗汉岭组凝灰岩与神农架群上亚群野马河组凝灰岩具有相似的Lu-Hf同位素特征：176Hf/177Hf初始值介于0.282 172~0.282 397,εHf(t)值为4.9~12.0, TCDM=1 150~1 943 Ma。结合现有区域地质资料,我们认为打鼓石群与神农架群上亚群属于同时期沉积物,形成于超级地幔柱主导的哥伦比亚超大陆裂解背景。  相似文献