| 张振凯,何元方,袁璋,仵桐,崔继岗,张清盛.南秦岭老城花岗闪长岩地球化学特征及地质意义[J].矿产勘查,2018,9(9):1713-1723 |
| 南秦岭老城花岗闪长岩地球化学特征及地质意义 |
| Geochemical characteristics of granodiorite from Laocheng pluton in south Qinling orogen and their geological significances |
| 投稿时间：2018-07-15 |
| DOI： |
| 中文关键词: 老城岩体 花岗闪长岩 I型花岗岩 岩浆混合 |
| 英文关键词: Laocheng pluton, granodiorite, I-type granites, magma mixing |
| 基金项目:陕西省宁陕县关口地区矿产远景调查(编号20150106)资助。 |
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| 中文摘要: |
| 为明确老城岩体花岗闪长岩的地球化学特征及岩石成因,对该类岩石进行了全岩主、微量、稀土元素测试。地球化学资料显示岩脉具有较高的硅含量(SiO2=63.42%~67.70%),富铝(Al2O3=15.38%~16.94%),富碱(Na2O+K2O=6.90%~7.86%),贫铁(TFe2O3=3.36%~4.97%)、镁(MgO=1.20%~2.68%)、钙(CaO=1.54%~3.48%)的特征,归类高钾钙碱性I型花岗岩；稀土元素总量较高(ΣREE=144.20×10-6 ~171.12×10-6),轻重稀土元素强烈分异,(La/Yb)N介于17.13~36.68之间,无明显Eu异常；微量元素以富集Rb、Pb、Th、U等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE)为特征。上述地球化学特征指示,花岗闪长岩为幔源物质底侵作用引发下地壳基性岩部分熔融形成的母岩浆,混合少部分幔源岩浆,经过分离结晶而形成。结合区域地质资料及同期岩浆岩活动,认为老城岩体中的花岗闪长岩形成于大陆弧环境。 |
| 英文摘要: |
| In order to clarify the geochemical characteristics and petrogenesis of Laocheng granodiorite pluton in South Qinling Orogen, whole rock major, rare earth and trace elements of the pluton, are investigated to identify the characteristics of geochemistry and petrogenesis, Geochemical, the rocks are relatively high in SiO2(63.42%~67.70%), Al2O3 (15.38%~16.94%) and alkali (6.90%~7.86%), but low in TFe2O3 (3.36%~4.97%), MgO(1.20%~2.68%) and CaO (1.54%~3.48%%), suggesting that they are high K calc-alkaline I-type granites. These rocks have relative high total REE concentration(ΣREE=144.20×10-6 ~171.12×10-6), with strong fractionation between light and heavy REE [(La/Yb)N=17.13~36.68] and no remarkable Eu anomalies. Furthermore, they are enriched in LILE (e.g., Rb, Pb, Th, U), and depleted in HFSE (e.g., Nb, Ta, Ti,). According to the geochemical characteristics, it is suggested that the granodiorite was generated by the crystal fractionation of parental magma mixed with small amount of mental magma, the parental magma is formed by patial metling of basic rocks in lower crust induced by mental material intrusion upward. Based on the regional geological investigations and spatial and time distribution of the coeval igneous rocks, it is considered that the granodiorite was emplaced in a continental arc environment. |
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