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冀北承德地区孤山二长闪长岩及其包体与捕虏体的岩石学与地质意义
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作者 路智 刘永顺 +2 位作者 钟爱丽 聂保锋 李赫 《地质科学》 CAS CSCD 北大核心 2023年第4期1414-1445,共32页
承德大庙地区的孤山闪长岩体是前寒武纪大庙斜长岩杂岩体伴生的岩体,其内含有不同类型的暗色包体以及超镁铁—镁铁质杂岩型捕虏体。孤山闪长岩体主要岩性为二长闪长岩,岩体含有二长闪长岩、黑云母辉石角闪石岩和斜长角闪岩型包体以及超... 承德大庙地区的孤山闪长岩体是前寒武纪大庙斜长岩杂岩体伴生的岩体,其内含有不同类型的暗色包体以及超镁铁—镁铁质杂岩型捕虏体。孤山闪长岩体主要岩性为二长闪长岩,岩体含有二长闪长岩、黑云母辉石角闪石岩和斜长角闪岩型包体以及超镁铁—镁铁质杂岩型捕虏体。超镁铁—镁铁质杂岩由黑云母辉石角闪石岩、斜长角闪岩、含有辉长闪长岩包体的大理岩等组成。孤山二长闪长岩体、包体和杂岩捕虏体普遍经历了绿帘角闪岩相变质,典型变质反应Cpx+Pl+H_(2)O→Amp_(2)+Ep+Ab±Chl。二长闪长岩体和包体中的角闪石有早、晚两期,早期角闪石是岩浆原生的,晚期变生角闪石与绿帘石围绕原生单斜辉石环带状生长,是由单斜辉石变生的。孤山二长闪长岩属于正常类型SiO_(2)不饱和岩石与偏铝质岩石,富集大离子亲石元素(如Sr、Ba和K)、亏损高场强元素(如Th、Nb、Ta、Zr、Hf和Ti),Rb和Y含量低,相容元素Ni、Cr含量低,V高,轻稀土富集,轻重稀土分异明显,Eu轻微正异常。与太古代TTG、高镁闪长岩、典型的赞歧岩类、芬兰和西格陵兰岛闪长岩、美国纽约州铁闪长岩以及西藏中生代的泽当闪长岩的对比研究表明,孤山二长闪长岩与西藏泽当闪长岩非常相似,微量和稀土元素具有赞歧岩质闪长岩的特点,应是俯冲环境产物。本研究对认识大庙斜长岩杂岩体的成因以及冀北地区构造演化有重要意义。 展开更多
关键词 孤山二长闪长 包体 铁—铁质型捕虏体 绿帘角闪 俯冲环境
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鄂西黄陵背斜南部元古宙庙湾蛇绿岩的发现及其构造意义 被引量:25
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作者 彭松柏 李昌年 +4 位作者 Kusky Timothy M 王璐 张先进 蒋幸福 熊承仁 《地质通报》 CAS CSCD 北大核心 2010年第1期8-20,共13页
对鄂西黄陵背斜南部宜昌太平溪、邓村一带崆岭岩群中的元古宙庙湾岩组强烈变形变质超镁铁—镁铁质岩的研究表明,镁铁质岩主要为似层状细粒斜长角闪岩,变辉长岩岩体、岩脉及辉绿岩岩脉,超镁铁质岩则主要为蛇纹石化纯橄榄岩、方辉橄榄岩,... 对鄂西黄陵背斜南部宜昌太平溪、邓村一带崆岭岩群中的元古宙庙湾岩组强烈变形变质超镁铁—镁铁质岩的研究表明,镁铁质岩主要为似层状细粒斜长角闪岩,变辉长岩岩体、岩脉及辉绿岩岩脉,超镁铁质岩则主要为蛇纹石化纯橄榄岩、方辉橄榄岩,呈构造岩片、岩块分布于斜长角闪岩之中。细粒斜长角闪岩TiO2=1.14%~1.48%,稀土元素配分型式为略亏损—平坦型,无明显的Eu异常,(La/Yb)N=0.87~1.12,La/Nb、Ce/Zr、Zr/Nb、Zr/Y、Ti/Y平均值分别为1.04、0.15、18.78、2.53、290.51,Nb/Th平均为9.88,显示为大洋中脊构造环境形成的N-MORB型拉斑玄武岩;变辉长岩具典型的堆晶结构特征,稀土元素配分型式为平坦型,具明显的Eu正异常;蛇纹石化纯橄榄岩的稀土元素配分型式具中稀土元素略亏损的U形特征,显示为LREE略富集的地幔岩。上述特征表明,黄陵背斜南部崆岭岩群中的元古宙庙湾岩组实际上是一套混杂堆积的古大洋蛇绿岩残片。元古宙庙湾蛇绿岩的发现为华南扬子克拉通存在中元古代洋盆和哥伦比亚超大陆聚合、裂解构造事件提供了重要的证据。 展开更多
关键词 湖北 黄陵背斜 元古宙庙湾蛇绿 超镁铁—镁铁质岩 构造意义
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Early Paleozoic granitic magmatism related to the processes from subduction to collision in South Altyn, NW China 被引量:30
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作者 LIU Liang KANG Lei +1 位作者 CAO YuTing YANG WenQiang 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第9期1513-1522,共10页
Four episodes of granitic rocks at 517, 501-496, 462-451, and 426-385 Ma occurred in the South Altyn subduction-collision complex. The first episode of granite emplacement predates the formation of the ophiolite type ... Four episodes of granitic rocks at 517, 501-496, 462-451, and 426-385 Ma occurred in the South Altyn subduction-collision complex. The first episode of granite emplacement predates the formation of the ophiolite type mafic rock (〉500 Ma), and the three subsequent episodes can be temporally correlated to high-pressure (HP) to ultrahigh-pressure (UHP) metamorphism at ca 500 Ma, retrograde granulite-facies metamorphism at ca. 450 Ma, and amphibolite-facies metamorphism at ca. 420 Ma, re- spectively. A comprehensive study of these granitic rocks, along with the regional geological background, mafic-ultramafic rocks, and HP-UHP metamorphism, indicates that the four episodes of granitic magmatism are sequentially derived from the partial melting of the earlier subducted oceanic crust at 517 Ma, the thickened continental crust due to continental subduction at ca. 500 Ma, the mid-upper crust in response to slab breakoff at ca. 450 Ma, and the tectonic transition from contraction to extension at ca. 420 Ma. The formation age of 517 Ma for oceanic adakite provides a direct constraint on the time of the oce- anic subduction in South Altyn. In addition, there is a ca. i0 Myr interval between the oceanic subduction to the continental deep subduction, suggesting that the Early Paleozoic tectonic evolution might have been a successive process in South Altyn. The four episodes of formation of granitic rocks, mafic-ultramafic rocks, and HP-UHP metamorphic rocks have fully recorded the tectonic evolution, beginning with the oceanic subduction, followed by continental subduction, and later exhumation dur- ing the Early Paleozoic in South Altyn. 展开更多
关键词 South Altyn granitic magmatism oceanic subduction continental deep subduction tectonic evolution
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Geochemical characteristics and tectonic setting of the Middle Permian Tiaohu Formation mafic-ultramafic rocks of Santanghu area, Xinjiang, Northwest China 被引量:7
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作者 WANG ShuangShuang LIU YiQun +3 位作者 ZHANG HongFu ZHOU DingWu JIAO Xin NAN Yun 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第11期1924-1938,共15页
Santanghu area in northeastern Xinjiang region of Northwest China is an important component of the Central Asian Orogenic Belt(CAOB), in which the dynamic mechanism of Permian magmatism is controversial. In Santanghu ... Santanghu area in northeastern Xinjiang region of Northwest China is an important component of the Central Asian Orogenic Belt(CAOB), in which the dynamic mechanism of Permian magmatism is controversial. In Santanghu area is exposed a thick succession of the Middle Permian basalts, including a small amount of picritic basalts and andesites, known as the Tiaohu Formation. The picritic basalts contain cumulate olivine, and have whole-rock Mg# up to 0.68–0.77; the basalts exhibit porphyritic or doleritic textures, and have relatively low Mg# of 0.41–0.54, typical of evolved magmas. The mafic-ultramafic rocks of the Tiaohu Formation are slightly enriched in Light Rare Earth Elements(LREEs), and exhibit negative Nb and Ti anomalies. They also have high Ti O2 content, and Nb/Y and Zr/Yb ratios greater than those of island arc volcanic rocks. Relatively low initial Sr isotopic ratios and high positive εNd(t) and εHf(t) values argue against contamination by ancient continental crust, and suggest formation of the Tiaohu Formation by partial melting of relatively refractory depleted lithospheric mantle that underwent metasomatism and extraction by fluid from the subducted slab. In addition, up to 38% olivine in picritic basalts indicates high-degree partial melting of lithospheric mantle, and the underlying Lucaogou Formation contains fragments of ultra-alkaline magmatic rocks that originated in the deep mantle. These observations imply wide-spread underplating in Santanghu area, which may have been associated with a mantle plume. 展开更多
关键词 Central Asian Orogenic Belt Santanghu Basin Middle Permian picritic basalts lithospheric mantle
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