江西相山酸性火山-侵入杂岩体地球化学特征与岩石成因
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国家自然科学基金项目(面上项目,重点项目,重大项目)


Geochemical Characteristics and Petrogenesis of the Acidic Volcano intrusive Complexes, Xiangshan, Jiangxi
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    摘要:

    相山火山盆地主体岩石为一套由熔结凝灰岩、流纹英安岩、碎斑熔岩、流纹英安斑岩、粗斑花岗斑岩及似斑状花岗岩组成的酸性火山-侵入杂岩体,具两个岩浆活动亚旋回。岩石具有富硅、富碱、低钙和低镁的特征,轻重稀土分异显著,稀土配分曲线呈四组分模式,具明显的负铕异常。各岩类之间具有相似的主、微量元素和同位素特征,指示了杂岩体各类岩石之间的同源性。流纹英安岩、碎斑熔岩、粗斑花岗斑岩及似斑状花岗岩的Nd模式年龄T2DM较为接近,分别为167Ga、166Ga、166Ga和163Ga,略低于残留锆石206Pb/238U年龄(17879Ma)和华夏地块出露的最古老岩石(斜长角闪岩)内的岩浆锆石SHRIMP U Pb年龄(1766±19 Ma),SiO2与P2O5呈明显的负相关关系,结合岩相学特征和Sr Nd的二元混合模式,推算出杂岩体的物质来源主要为上地壳中元古代基底变质岩部分熔融的结果,有少量幔源的参与(平均含量为2282%)。每期亚旋回不同岩类之间随着成岩先后顺序,Na2O和K2O含量逐渐增高,但SiO2含量逐渐降低,表现出反序演化特征,可能表明岩浆房内发生过正常的分异作用,反映岩浆房内酸性成分在上偏基性成分在下的分布状况,第一亚旋回的末期或者暂歇期又有酸性岩浆的重新加入。第一亚旋回分异程度较强,以分离斜长石和钾长石为主,第二亚旋回以分离钾长石为主。燕山晚期江西境内的地球动力学背景并不是一致的,有由南向北逐渐演化为板内裂谷的趋势。相山地区在141~132Ma之间表现为陆内造山后的伸展阶段,在125Ma附近逐渐演化为板内裂谷环境。

    Abstract:

    The Xiangshan volcanic basin comprises volcano intrusive complexes that are composed of tuff, rhyolite dacite, porphyry rhyolitic dacite, porphyroclastic lava, coarse grained porphyry and porphyritic granite. The paper discussed the origin and evolution of these igneous rocks based on their whole rock major and trace elements, as well as Pb Sr Nd isotopes. Different lithologies have similar elemental and isotopic compositoins, indicating that they were derived from the same source region. The rocks are rich in silicon and alkali, low in calcium and magnesium. LREE and HREE differentiate significantly, REE distribution curve presents four component model and obvious negative Eu. Nd model ages(T2DM) of rhyodacite, Porphyroclastic Lava, rough spots granite porphyry and porphyritic granite is closer, respectively 167Ga, 166Ga, 166Ga and 163Ga, slightly lower than the residual zircon 207Pb/206Pb age (17879Ma) and the the oldest rocks exposed (amphibolite) of Cathaysian Block within the magmatic zircon SHRIMP U Pb age of (1766 ± 19Ma). There is a negative correlation between SiO2 and P2O5, combining the facieology and the two element mixed mode petrography of Sr Nd, calculating that the material source of the complexes has a small amount of mantle source involved, the average content of 2282%.; each sub cycle between the different rock types with diagenesis sequence, Na2O and K2O increased, but SiO2 content decreased gradually, may indicate that the magma has occurred in the differentiation of normal. acidic component is on the upside, and the partial distribution of basic components at the bottom, at the end of the first sub cycle or timeout period, acidic component join in the magma. The first subcycle variation degree is strong, the separation of plagioclase and potash feldspar, at the second sub cycles, mainly potassium feldspar. At the late Yanshan, Jiangxi in the dynamic background of the earth is different, gradually evolved into intra plate rift trend from south to north. In 141Ma~132Ma the Xiangshan area is post orogenicr, in the vicinity of 125Ma gradually evolved into an intraplate rift environment.

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郭福生,杨庆坤,孟祥金,谢财富,时国,陈留勤,蒋振频,曾涛,罗能辉.2016.江西相山酸性火山-侵入杂岩体地球化学特征与岩石成因[J].地质学报,90(4):769-784.
GUO Fusheng, YANG Qingkun, MENG Xiangjin, XIE Caifu, SHI Guo, CHEN Liuqin, JIANG Zhenpin, ZENG Tao, LUO Nenghui.2016. Geochemical Characteristics and Petrogenesis of the Acidic Volcano intrusive Complexes, Xiangshan, Jiangxi[J]. Acta Geologica Sinica,90(4):769-784.

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  • 收稿日期:2014-07-31
  • 最后修改日期:2014-10-23
  • 录用日期:2016-04-26
  • 在线发布日期: 2016-04-26
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