Early Mesoproterozoic bimodal plutonism in the southeastern Gawler Craton,South Australia     

W. L. Zang  C. M. Fanning  A. C. Purvis  O. L. Raymond  R. A. Both 《Australian Journal of Earth Sciences》2013,60(5):661-674

The Curramulka Gabbronorite on Yorke Peninsula, southeastern Gawler Craton has an emplacement age of 1589 ± 5 Ma. This is similar to previously determined ages for Arthurton Granite (1582 ± 7 Ma), Tickera Granite (ca 1600 – 1575 Ma), regional alteration, the Moonta – Wallaroo mineralisation (ca 1585 Ma) and localised deformation (Tiparra Deformation). Mesoproterozoic bimodal plutonism is interpreted to have resulted from mafic underplating, emplacement of mafic magmas during lithospheric attenuation and enhanced high heat flow assisting in melting of the lower crust to form the broadly A-type Arthurton and Tickera Granites. Plutonism either directly or indirectly created advective fluid-flow to form Cu – Au mineralisation in the Moonta – Wallaroo area. The nature and characteristics of Mesoproterozoic mafic bodies on the Gawler Craton are poorly known. The Curramulka Gabbronorite has a continental tholeiitic composition and igneous layering that is partly of cumulus origin but also contains magmatic segregations formed by fractionation. Some of these segregations have provided zircons for dating. This igneous layering is overprinted by two foliations of tectonic origin: the first is interpreted to be coeval with magma emplacement and the second with conjugate shearing accompanied by retrogression.  相似文献   

勉略构造带横现河地区张岩沟双峰式火山岩的地球化学特征、LA-ICP-MS锆石U-Pb年龄及其构造意义   总被引：1，自引：0，他引：1       下载免费PDF全文

徐 通裴先治  李瑞保李佐臣 裴 磊刘成军  陈有炘汪晓伟 杨 杰 胡 楠 《中国地质》2013,40(6):1777-1792

提要：横现河地区张岩沟双峰式火山岩位于勉略构造带三岔子—略阳段,由紧密共生的变质基性火山岩和变质中酸性火山岩组成,其原岩为亚碱性玄武岩和亚碱性流纹-英安岩。中酸性火山岩稀土元素含量明显低于玄武岩,表明中酸性火山岩为地壳部分熔融形成,而非分离结晶成因。玄武岩具有较高的Zr含量与较高的Zr/Y值,表现出板内玄武岩特征,其具有的弧印记应为陆壳物质混染所致。LA-ICP-MS锆石U-Pb测试结果表明,流纹岩成岩年龄为(728±10) Ma (n=4,MSWD =0.14)。结合区域地质背景,认为张岩沟双峰式火山岩形成于地壳伸展机制下的大陆裂谷环境,预示着该地区新元古代洋盆的打开。这一新成果,对研究勉略带新元古代的构造演化以及探讨扬子地块北缘对Rodinia超大陆裂解的响应具有重要意义。  相似文献   

新疆富蕴地区中泥盆统阿勒泰组喀腊曼哲火山岩地球化学特征及构造环境研究     

张亚峰  蔺新望  郭岐明  吕军利  赵端昌  王星  王旭  党晨  申维娜 《西北地质》2013,(4):66-80

通过野外调研和相关地球化学研究,表明出露于阿尔泰造山带南缘富蕴地区喀腊曼哲一带的中泥盆统阿勒泰组火山岩由玄武岩和流纹岩组成,为一套典型的双峰式火山岩组合。其中,玄武岩多变质为钠长阳起片岩、绿帘透闪片岩等,属拉斑玄武岩系列,低SiO2、K2O,高Ti,稀土配分曲线显示轻稀土略富集的平坦型,无明显Eu异常（SEu=0．92～1．08）,富Th、U等,Nb负异常;流纹岩属钙碱性系列,高SiO2,低K2O,为钠质型,稀土配分曲线显示Eu负异（dEu为0．29～0．58）的右倾型,富集Th、U、La、Ce和Hf,亏损Sr、Nb、Ta、Zr、P、Ti。二者地球化学特征存在明显差异,表明酸性火山岩并不是由基性岩浆分离结晶产生,而可能是与基性下地壳经不同程度的部分熔融有关;基性火山岩为经俯冲流体改造的亏损地幔部分熔融的产物。岩石地球化学分析结果虽然显示其兼具洋中脊和岛弧火山岩的地球化学特征,但结合区域地质背景,其可能并不是形成于弧后盆地环境,而是岛弧裂谷的产物,属于成熟岛弧。  相似文献   

闽中地区马面山群东岩组变质岩形成的古构造环境研究   总被引：9，自引：0，他引：9  

张达  吴淦国  彭润民  吴建设  狄永军  张祥信  汪群峰 《地学前缘》2005,12(1):310-320

闽中地区马面山群东岩组地层主要为绿片岩为主的一套古火山沉积建造。其主要岩性类型包括各种成分的绿片岩、大理岩、石英片岩及变粒岩类。绿片岩显示海底火山喷发特征,变粒岩原岩为中酸性岩类。东岩组变质岩岩石化学研究表明,绿片岩的原岩应为玄武岩类。变粒岩类主要属于英安岩及流纹岩。这些特征反映东岩组具双峰式火山岩特征,形成于大陆内部张性环境。绿片岩稀土元素特征也显示和大陆拉张环境中的火山岩类稀土特征非常相似,属大陆拉斑玄武岩;微量元素分布显示出该组变质岩原岩类似于大洋岛和大陆裂谷的板内碱性玄武岩。因此闽中地区中元古代可能处于板内古裂谷环境。  相似文献   

Ordovician sedimentation and bimodal volcanism in the Southern Qiangtang terrane of northern Tibet: Implications for the evolution of the northern Gondwana margin   总被引：2，自引：0，他引：2  

Chao-ming Xie  Cai Li  Jian-jun Fan  Li Su 《International Geology Review》2017,59(16):2078-2105

This article reports our new interpretations of the depositional environment and provenance of the Dawashan Formation in the Longmuco–Shuanghu–Lancangjiang suture zone (LSLSZ), in the Southern Qiangtang terrane of northern Tibet, in order to gain a better understanding of the Ordovician tectonic evolution of the northern margin of Gondwana. The Dawashan Formation is dominated by greywacke and shale, with interlayered bimodal volcanic rocks that were deposited in a bathyal to abyssal marine basin. The detrital zircons in the greywacke of the Dawashan Formation have peak ages of 550, 988, 1640, and 2500 Ma, indicating a northern Gondwana margin provenance. The bimodal metavolcanic rocks from the Dawashan Formation are dominated by metarhyolite with subordinate metabasalt. The results of zircon LA-ICP-MS U–Pb dating indicate that the metarhyolite formed between 470 and 455 Ma. The metavolcanic samples are bimodal (SiO₂ = 45.27–55.05 and 66.09–74.59 wt.%). In comparison, the metabasalt has a wide range of MgO concentrations and Mg^# values, contains variable Cr and low Ni concentrations, is depleted in Rb, Ba, and Sr, and is enriched in TiO₂, Th, U, Nb, and Ta. Geochemical diagrams show that the metabasalt erupted in an intra-plate environment. The metarhyolites have high SiO₂, Th, and U concentrations, low concentrations of MgO, P₂O₅, Nb, Sr, and Ti, and negative Eu anomalies. The metarhyolites yield negative zircon ε_Hf(t) values (–2.08 to – 4.50) and T^C_DM model ages of 1436–1567 Ma. The metarhyolites formed from magma derived from the partial melting of old continental crust. These data indicate that the Dawashan Formation records Middle–Upper Ordovician bathyal to abyssal turbidite deposition in a deep-water rift basin at the northern margin of Gondwana.  相似文献   

伊宁地块特克斯达坂晚石炭世伊什基里克组双峰式火山岩地球化学特征   总被引：1，自引：0，他引：1  

宁文涛  李永军  汪振宇  王祚鹏  李甘雨 《岩石矿物学杂志》2019,38(1):1-20

伊宁地块特克斯达坂一带出露的晚石炭世伊什基里克组双峰式火山岩主要由玄武岩、流纹岩两大端员组成,其Si O2含量为47. 13%～77. 72%,在53. 62%～72. 15%之间存在明显的间断,具有双峰式火山岩的特征。LAICP-MS锆石U-Pb定年获得流纹岩年龄为302. 8±3. 6 Ma,表明该套火山岩形成于晚石炭世。玄武岩Si O2含量为47. 13%～53. 62%,具有低Si O2、高Fe2O3(TFe2O3=10. 90%～17. 40%)、高MgO(3. 74%～10. 12%,平均为6. 48%)和高Na(Na2O=2. 84%～6. 69%)、低K(K2O=0. 48%～3. 77%)特征(Na2O/K2O=1. 21～12. 18),轻稀土元素富集而重稀土元素亏损[(La/Yb)N=1. 58～4. 94],具有弱的负Eu异常(δEu=0. 30～1. 10),亏损Ta、Nb、Th、Sr等不相容元素。流纹岩Si O2含量为72. 15%～77. 72%,具有高Si O2、高K(K2O=6. 12%～9. 48%)、低Na(Na2O=0. 40%～2. 39%)特征(Na2O/K2O=0. 04～0. 36),K、Rb和LREE显著富集[(La/Yb)N=2. 46～10. 48],相对亏损Ba、Sr、P、Ti,且有基本一致的强负Eu异常(δEu=0. 18～0. 44),具有A2型花岗岩地球化学特征。此外,玄武岩具有相对高的Mg#值和Co、Cr、Ni含量,其εNd(t)值为3. 45、3. 55,表明玄武岩来自于亏损地幔的部分熔融;而流纹岩具有低Mg#和正εHf(t)值,暗示其形成与玄武质岩浆底侵过程中的地壳熔融有关。结合二阶段锆石Hf模式年龄,认为源区可能与元古宙的变质结晶基底重熔有关。根据上述地球化学特征并结合构造判别图解,认为特克斯达坂一带伊什基里克组双峰式火山岩形成于造山后伸展环境,具有板内成因特征。该套典型双峰式火山岩的发现为进一步探讨伊宁地块石炭纪构造演化提供了重要依据。  相似文献   

云和盆地早白垩世双峰式火山岩特征     

杨晓春 《浙江国土资源》1996,(2)

本文从岩石学、岩石化学、微量元素及稀土元素等方面，对云和盆地早白垩世馆头组火山岩特征进行了论述，并对其形成环境及成因作了探讨．认为该套火山岩由基性岩及酸性岩构成，缺少SiO2含量在53．17％～68．57％的中性岩，是一套典型的双峰式火山岩组合。指出盆地内火山岩为拉张构造背景下形成，其基性岩和酸性岩具有不同源区，前者源于部分上地幔融熔物质（受陆壳物质混染）；后者来自部分地壳融熔的产物。  相似文献   

新疆阿舍勒铜矿区双峰式火山岩与成矿背景的初步研究   总被引：13，自引：1，他引：13  

王登红 《地质论评》1996,42(1):45-53

新疆阿舍勒铜矿是我国近十多年来找到的一个大型海相火山岩型块状硫化物多金属矿床，在经济上和矿床学上都有重要意义。阿舍勒铜矿的容矿岩是早－中泥盆世阿舍勒组海相火山岩，具特征的双峰式组合，缺少含ＳｉＯ２５４％－６１％的中性岩，在地表和钻孔都经常见到基性与酸性火山岩紧密互层现象。稀土和微量元素地球化学表明基性、酸性火山岩来自两个不同的源区。矿石铅同位素组成与细碧岩一致，硫同位素呈典型塔式分布，表明成矿物质  相似文献   

双峰式火山岩与块状硫化物矿床   总被引：13，自引：0，他引：13  

姜福芝 《矿床地质》2001,20(4):331-338

双峰式火山岩不仅是火山成因块状硫化物矿床中最常见的含矿岩石组合，而且也是研究其古成矿地质背景和成矿作用的主要依据之一。笔者收集了我国以及世界一些著名火山成因块状硫化物矿床和矿带的含矿建造资料，其中包括含矿建筑的岩石组合、形成时代和层序、火山岩的岩石组合和岩石化学、产出的大地构造环境等等。整理结果表明，双峰式火山岩是火山成因块状硫化物矿床的最佳含矿岩石组合；它们主要产五各个时期的造山火山岩类，产生了有利成矿组分浓集的巨大热液循环系统及适宜原（海水深度和封闭条件良好的）含矿流体集积的沉陷盆地（裂谷），从而为成群成带的VHMS型矿床的形成提供了有利的地质环境。  相似文献   

Geochemistry and Petrogenesis of Volcanic Rocks in the Yeba Formation on the Gangdise Magmatic Arc, Tibet     

Geng Quanru Pan Guitang Jin Zhenmin Wang Liquan Liao Zhongli 《中国地质大学学报(英文版)》2005,16(4):283-296

The Early Jurassic bimodal volcanic rocks in the Yeba Formation, situated between Lhasa, Dagzê and Maizhokunggar, composed of metabasalt, basaltic ignimbrite, dacite, silicic tuff and volcanic breccia, are an important volcanic suite for the study of the tectonic evolution of the Gangdise magmatic arc and the Mesozoic Tethys. Based on systematic field investigations, we carried out geochemical studies on representative rock samples. Major and trace element compositions were analyzed for these rock samples by XRF and ICP-MS respectively, and an isotope analysis of Rb-Sr and Sm-Nd was carried out by a MAT 262 mass spectrograph. The results show that the SiO2 contents in lava rocks are 41 %-50.4 % and 64 %-69 %, belonging to calc-alkaline basalt and dacite. One notable feature of the basalt is its low TiO2 content, 0.66 %-1.01 %, much lower than those of continental tholeiite. The ΣREE contents of basalt and dacite are 60.3-135 μg/g and 126.4-167.9 μg/g respectively. Both rocks have similar REE and other trace element characteristics, with enriched LREE and LILE relative to HREE and HFS, similar REE patterns without Eu anomaly. The basalts have depleted Ti, Ta and Nb and slightly negative Nb and Ta anomalies, with Nb*＝0.54-1.17 averaging 0.84. The dacites have depleted P and Ti and also slightly negative Nb and Ta anomalies, with Nb*＝0.74-1.06 averaging 0.86. Major and trace elemental and isotopic studies suggest that both basalt and dacite originated from the partial melting of the mantle wedge at different degrees above the subduction zone. The spinal lherzolite in the upper mantle is likely to be their source rocks, which might have been affected by the selective metasomatism of fluids with crustal geochemistry. The LILE contents of both rocks were affected by metamorphism at later stages. The Yeba bimodal volcanic rocks formed in a temporal extensional situation in a mature island arc resulting from the Indosinian Gangdise magmatic arc.  相似文献