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为了弄清楚勉略构造带中三岔子岛弧火山岩的形成时代及源区特征,对南秦岭勉略缝合带三岔子岛弧蛇绿混杂岩中的辉绿岩墙样品进行了锆石U—PB年代学、锆石Hf同位素组成及微量元素组成研究。结果表明,三岔子辉绿岩中的锆石主要包括2个年龄区间：有8颗锆石记录古生代年龄信息,其n（205Pb）／n（238u）年龄为264～487Ma,Ⅷ（Th）／w（U）为0．4～0．8,其中有6颗锆石的N（176Hf）／N（177Hf）初始值为0．281934～0．282292,埘应的EHf（f）值为9．4～-16．4,为典型的壳源岩浆锆石,另外2个测点（BQG-014,BQG-021）的N（176Hf）/N（177Hf）为0．282722～0．282798,对应的εHf（f）值为4．5～6．3,为典型的幔源岩浆锆石;有15颗锆石记录厂元古代-太古代的年龄信息,N（207Pb）/N（206Pb）年龄主要为1713～2559Ma,N（176Hf）／N（177Hf）初始值为0．281288～0．282263,对应的εHf（t）值为-1．3～8．7,绝大部分锆石的εHf（t）值大于2,显示出幔源岩浆锆行的特征。根据锆石Hf同位素组成,BQG-014和BQG-021样品为典型的幔源岩浆锆石,因此,其形成年龄（264～295Ma）应代表了勉略洋消减过程中一次重要的大陆弧岩浆作用时间。 相似文献
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钦州湾-杭州湾构造结合带（南段）
地质演化和找矿方向 总被引：22，自引：0，他引：22
钦州湾-杭州湾结合带是位于扬子与华夏两大古陆块中间的巨型构造结合带。根据内部结构不均一性和演化历史的差异,钦-杭结合带可划分为3段：北（东）段、中段和南（西）段,分界线大致为北纬24°和北纬27°。中段与南岭带大体一致;北段指南岭以北地区,即绍兴-江山-萍乡一带;南段位于南岭以南区域,大致与云开-十万大山带相当。钦-杭结合带南段是华南大陆壳再造和矿产资源寻找的重要研究课题。它的地质演化与钦-杭结合带具有整体一致性,特别是具有一致的开-合历史。震旦系底部的粤西云浮大降坪块状硫化物矿床是海底喷流沉积的产物,它与信宜和陆川新元古代蛇绿岩等是南段洋壳存在的重要证据。在进一步的矿床勘查中,要重视斑岩型铜（钼）矿床的寻找。中酸性斑岩体来自于元古宙岛弧底部玄武质岩石（下地壳）在中生代时期的部分熔融,本质上该类矿床带有岛弧俯冲环境的基因。 相似文献
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钦州湾-杭州湾构造结合带（南段）地质演化和找矿方向 总被引：14，自引：0，他引：14
钦州湾-杭州湾结合带是位于扬子与华夏两大古陆块中间的巨型构造结合带。根据内部结构不均一性和演化历史的差异,钦-杭结合带可划分为3段：北（东）段、中段和南（西）段,分界线大致为北纬24°和北纬27°。中段与南岭带大体一致;北段指南岭以北地区,即绍兴-江山-萍乡一带;南段位于南岭以南区域,大致与云开-十万大山带相当。钦-杭结合带南段是华南大陆壳再造和矿产资源寻找的重要研究课题。它的地质演化与钦-杭结合带具有整体一致性,特别是具有一致的开-合历史。震旦系底部的粤西云浮大降坪块状硫化物矿床是海底喷流沉积的产物,它与信宜和陆川新元古代蛇绿岩等是南段洋壳存在的重要证据。在进一步的矿床勘查中,要重视斑岩型铜（钼）矿床的寻找。中酸性斑岩体来自于元古宙岛弧底部玄武质岩石（下地壳）在中生代时期的部分熔融,本质上该类矿床带有岛弧俯冲环境的基因。 相似文献
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拉萨地体南缘的晚三叠世—中侏罗世岩浆岩被认为是新特提斯洋早期北向俯冲的岩浆记录,并形成与之相关的雄村特大型斑岩-浅成低温热液铜-金矿床。对该时期岩浆岩成因背景的研究有助于评价其成矿潜力。选取拉萨地体南缘日喀则西北部花岗岩类进行锆石U-Pb测年及Lu-Hf同位素分析。花岗岩类LA-ICP-MS锆石U-Pb定年结果为175~180.1Ma,εHf(t)平均值为+13.4,显示幔源特征,为岛弧(洋内弧)背景成因,具有斑岩铜金成矿潜力。结合前人对拉萨地体南缘晚三叠世—白垩纪岩浆岩的研究,认为拉萨地体南缘未被剥蚀的晚三叠世—白垩纪火山岩中有可能保存有新特提斯洋俯冲形成的斑岩铜金成矿系统。 相似文献
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A.O. Volynets M.M. Pevzner M.L. Tolstykh A.D. Babansky 《Russian Geology and Geophysics》2018,59(12):1577-1591
Based on the geochemical characteristics of the Miocene-Quaternary volcanic rocks of the Sredinny Range of Kamchatka, we divide it into northern and southern provinces; the latter comprises the “eastern”, “western”, and “central” flanks. We present new data on the composition of Neogene-Quaternary volcanic rocks in the southern part of the Sredinny Range of Kamchatka: Khangar and Icha volcanic massifs and Mt. Yurtinaya on the “western” flank, Bystrinsky and Kozyrevsky Ridges on the “eastern” flank, and Anaunsky Dol and Uksichan massif located in between. We show systematic differences in the composition of rocks from the “western” and “eastern” flanks. During the Neogene, a typical island-arc volcanism took place within the “eastern” flank. Quaternary volcanic rocks of this area have both island-arc and within-plate geochemical features. We propose to call rocks of this type hybrid rocks. Within the “western” flank, hybrid volcanism has been manifested since the Neogene, while typical island-arc rocks are not found. Magma generation processes on the “western” flank of the Sredinny Ridge are influenced by an enriched mantle source; the effect of fluid is less pronounced here as compared to the rocks of the “eastern” flank, where it is clearly traced. 相似文献
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东天山小石头泉铜多金属矿区火山岩-次火山岩地球化学与成矿构造背景 总被引：1，自引：0，他引：1
小石头泉铜多金属矿位于新疆哈密市东北200km,在区域地质构造上处于东天山哈尔里克岛弧东段。本文主要对矿区火山岩的主量、微量元素及同位素组成进行测试和研究。含矿岩石以流纹斑岩、英安岩、英安斑岩为主,SiO_2含量为51.96%～72.58%,Na_2O K_2O 为3.1%～7.73%,计算里特曼指数σ<3.3,显示具有钙碱性岩的特征;稀土元素配分形式为轻稀土相对富集,其中英安岩 Eu 负异常比安山岩更为明显,说明源区有斜长石的残留或岩浆演化经历了结晶分异作用;微量元素具有典型的岛弧火山岩的地球化学特征,如 Ta、Nb、Ti 等元素较板内火山岩的明显亏损;岩石初始锶(~(87)Sr/~(86)Sr)_i 平均值为0.7043,εNd(t)为4.7,反映火山岩形成源区以幔源为主,混有部分壳源物质。以上岩石地球化学研究结果表明,该区火山岩形成于火山岛弧环境。通过与东天山大南湖岛弧火山岩对比,发现两地区的同时代火山岩地球化学属性存在一定差异,大南湖岛弧火山岩区以发育 Adakite 岩为特征,而哈尔里克岛弧缺少Adakite 岩,可能反映该区火山岩的形成与部分熔融的洋壳交代地幔楔有关。本文认为小石头泉地区为典型火山岛弧环境,有利于火山热液型多金属矿床的形成。 相似文献
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Processes of magma/wet sediment interaction in a large-scale Jurassic andesitic peperite complex, northern Sierra Nevada, California 总被引：3，自引：0，他引：3
The Middle Jurassic Tuttle Lake Formation in the northern Sierra Nevada, California, comprises a thick volcaniclastic sequence
deposited in a submarine island-arc setting and penetrated by numerous related hypabyssal intrusions. A composite andesite-diorite
intrusive complex ≥4.5 km long and ≥1.5 km thick was emplaced while the host Tuttle Lake sediments were still wet and unconsolidated.
Large parts of the intrusive complex consist of peperite formed where andesitic magma intruded and intermixed with tuff, lapilli-tuff
and tuff-breccia. The southern half of the complex consists of augite-phyric andesite containing peperite in numerous small,
isolated pockets and in more extensive, laterally continuous zones. The peperites comprise three main types recognized previously
in other peperite studies. Fluidal peperite consists of small (≤30 cm), closely spaced, at least partly interconnected, globular to amoeboid andesite bodies enclosed
by tuff. This peperite type developed during intrusion of magma into fine-grained wet sediment along unstable interfaces,
and fluidization of the sediment facilitated development of complex intrusive geometries. Blocky peperite and mixed blocky and fluidal peperite formed where magma intruded coarser sediment and underwent variable degrees of brittle fragmentation by quenching and dynamic
stressing of rigid margins, possibly aided by small steam explosions. The northern half of the intrusive complex consists
predominantly of a different type of peperite, in which decimetre-scale plagioclase-phyric andesite clasts with ellipsoidal,
elongate, or angular, polyhedral shapes are closely packed to widely dispersed within disrupted host sediment. Textural features
suggest the andesite clasts were derived from conduits through which magma was flowing, and preserved remnants of the conduits
are represented by elongate, sinuous bodies up to 30 m or more in length. Disruption and dispersal of the andesite clasts
are inferred to have occurred at least partly by steam explosions that ripped apart a network of interconnected feeder conduits
penetrating the host sediments. Closely packed peperite is present adjacent to mappable intrusions of coherent andesite, and
along the margin of a large mass of coarse-grained diorite. These coherent intrusions are considered to be major feeders for
this part of the complex. Examples of magma/wet sediment interaction similar in scale to the extensive peperites described
here occur elsewhere in ancient island-arc strata in the northern Sierra Nevada. Based on these and other published examples,
large-scale peperites probably are more common than generally realized and are likely to be important in settings where thick
sediment sequences accumulate during active volcanism. Careful mapping in well-exposed terrains may be required to recognize
large-scale peperite complexes of this type.
Received: 8 June 1998 / Accepted: 4 December 1998 相似文献
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１９９５年第二季度，全球地震活动恢复到１９９４年的高水平态势：浅源地震频数猛增，并出现两次Ｍｓ７．７以上巨大地震。大洋岛弧带成为本季度地震活动中心。所罗门群岛有两次中强震。菲律宾萨马岛附近发生大震群。千岛群岛大震的余震未息。秘鲁北部和缅印边界各有一次中深源地震。希腊发生中强地震两次。萨哈林岛地震显示全球地震信息。 相似文献
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Petrology, chronology and isotope geochemistry of the proterozoic amphibolites from Xiangshan, central Jiangxi province, China 总被引：2，自引：0，他引：2
On the basis of a comprehensive study on the petrology,trace elements and isotopic geochemistry of the Xiangshan amphibolites,we suggest that the protoliths of the amphibolites were basalts formed in an island-arc tectonic setting.The basaltic magma was derived from a slightly depleted mantle source with a small amount of crustal contamination.Assemblage of the rock-froming minerals indicates that these amphibolites underwent a low-grade metamorphism of amphibolite facies.According to the formation age(1113Ma) and subsequent metamophic age(726.6Ma) of the basalts aw well as the geological and gochemical features of these amphibolites,a tectonic model of Proterozoic oceanic island-arc setting is proposed for central Jiangxi. 相似文献