赣杭构造带中西段中生代基性脉岩地球化学特征

赣杭构造带中西段中生代基性脉岩地球化学特征

齐有强^1，2，胡瑞忠¹，刘燊¹，戚华文¹，冯彩霞¹

1.中国科学院地球化学研究所/矿床地球化学国家重点实验室, 贵阳 550002;2.中国科学院研究生院, 北京 100039

收稿日期:2008-05-22 修回日期:1900-01-01 出版日期:2008-09-26 发布日期:2008-09-26
通讯作者: 齐有强

Geochemical Characteristics of the Mafic Dikes from the Gan-Hang Tectonic Belt

QI You-qiang^1,2, HU Rui-zhong¹, LIU Shen¹,QI Hua-wen¹, FENG Cai-xia¹

1.Institute of Geochemistry/State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;2.Graduate University, Chinese Academy of Sciences, Beijing 100049, China

Received:2008-05-22 Revised:1900-01-01 Online:2008-09-26 Published:2008-09-26
Contact: QI You-qiang

摘要/Abstract

摘要： 赣杭构造带中西段发育的基性脉岩以辉绿岩为主，SiO₂质量分数为46.88%~53.69%，从西段至中段总体显示亚碱性至碱性的变化规律。微量元素相对富集大离子亲石元素(LILE)和轻稀土元素(LREE)，亏损高场强元素(HFSE)和重稀土元素(HREE)。稀土元素总量具有明显的规律性分布，即呈中段（广丰）-中西段交接部（余江、东乡）-西段（永丰、峡江）的递减趋势。西段永丰地区有明显的负Eu异常。Sr、Nd同位素变化比较大((⁸⁷Sr/⁸⁶Sr)_i为0.704 635~0.708 769, (¹⁴³Nd/¹⁴⁴Nd)_i为0.512 173~0.512 758,ε_Nd(t)为-6.8~+5.6)，暗示其源区具有明显的不均一性。具体表现为中西段结合部（东乡、余江）及西段（峡江）为亏损地幔，而西段（永丰）和中段（广丰）为偏向EMⅡ型富集地幔来源。基性脉岩总体表现为地幔部分熔融的产物，西段（永丰）受到较明显的分离结晶作用影响。在古太平洋板块俯冲影响下产生的弧后拉张作用以及造成的构造带重新活化作用对基性脉岩的形成产生了重要影响，地区间岩石地球化学特征上的差异主要与流体对岩浆源区交代程度的不同有关。

关键词: 赣杭构造带, 基性脉岩, 地球化学特征, 流体交代

Abstract: The SiO₂ content of the mafic dikes from Gan-Hang tectonic belt ranges from 46.88% to 53.69%. The dolerites from middle and west of Gan-Hang(Jiangxi-Zhejiang) tectonic belt belong to sub-alkaline and alkaline series, respectively. The trace elements of the mafic dikes are characterized by enrichment in LREE and LILE (Ba, Rb and K) and depletion in HREE and HFSE (Ta, Nb, Zr, Hf and Ti). The REE of the mafic dikes decreases gradually from Guangfeng to Yujiang and Dongxiang, and then to Yongfeng and Xiajiang. The mafic dikes from Yongfeng have obviously Eu anomalies. The Sr and Nd isotopic composition of mafic dikes are of a wide range, (⁸⁷Sr/⁸⁶Sr)_i varying from 0.704 635 to 0.708 769, (¹⁴³Nd/¹⁴⁴Nd)_i from 0.512 173 to 0.512 758, and ε_Nd(t) from -6.8 to +5.6, revealing that the mafic dikes were derived from partial melting of different magma sources. The mafic dikes from Yujiang, Dongxiang and Xiajiang were derived from depleted mantle, while the mafic dikes from Guangfeng and Yongfeng were produced by partial melting of EMⅡ-type enriched mantle due to mantle metasomatism. In addition, there occurred fractional crystallization of olivine, clinopyroxenes, plagioclase and Ti-Fe oxide during the magma ascent. The mafic dikes were related with the subduction of the Paleo-Pacific, different tectonic locations may account fro their different petrologic characteristics.

Key words: Gan-Hang tectonic belt, mafic dikes, geochemical characteristics, metasomatism

中图分类号:

P588.13

齐有强，胡瑞忠，刘燊，戚华文，冯彩霞. 赣杭构造带中西段中生代基性脉岩地球化学特征[J]. J4, 2008, 38(5): 784-0794.

QI You-qiang, HU Rui-zhong, LIU Shen,QI Hua-wen, FENG Cai-xia. Geochemical Characteristics of the Mafic Dikes from the Gan-Hang Tectonic Belt[J]. J4, 2008, 38(5): 784-0794.

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