A SIMS study of lithium, boron and chlorine in basalts from Reykjanes (southwestern Iceland)
A SIMS study of lithium, boron and chlorine in basalts from Reykjanes (southwestern Iceland)
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对雷克雅内斯（冰岛西南部）玄武岩中锂、硼和氯的 SIMS 研究
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发表时间：
2008
期刊：
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通讯作者：
G. Fridleifsson
中科院分区：
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作者：
N. Raffone;L. Ottolini;S. Tonarini;G. Gianelli;G. Fridleifsson
冰岛是地球上少数几个可以在陆地上研究热液蚀变对大洋地壳玄武岩影响的地方之一。在此框架下，我们进行了一些所谓的热液标志物，如轻亲石（Li，B）和卤素（Cl）元素的浓度测定的微观分析研究。通过离子探针对三个钻孔切割样品中的岩浆相（斜长石和单斜辉石）进行了研究，这些样品是根据不同深度（400-3000米）选择的，来自RN-17井的一个未蚀变熔岩和RN-19井的一个岩心样品（粗玄岩岩墙），所有这些样品都位于冰岛西南部的Reykjanes地热田内。此外，整个岩石上的B和Li被用来更好地约束热液过程。全岩Li和B数据表明，所研究的样品主要受海水热液蚀变的影响。相反，全岩和矿物相（斜长石和单斜辉石）中B含量的差异以及单矿物之间Cl含量的差异，可能是由于与热液蚀变有关的第二相（如绿帘石和角闪石）的出现，沿着裂隙带流体循环的影响。
Abstract.Iceland is one of the few places on earth where it is possible to study on land the effects of hydrothermal alteration on basaltic rocks from oceanic crust. In this frame, we have carried out a micro-analytic study on determining the concentrations of some of the so-called hydrothermal markers, such as the light lithophile (Li, B) and halogen (Cl) elements. They were investigated by the ion microprobe on magmatic phases (plagioclase and clinopyroxene) in three drill-cutting samples, selected on the basis of different depths (400–3000 m), in one unaltered lava from the well RN-17, and one core sample (dolerite dyke) from well RN-19, all of them located within the Reykjanes geothermal fields in SW Iceland. Additionally, B and Li on whole rock were then utilized to better constrain the hydrothermal processes. Whole rock Li and B data have shown that the samples investigated were affected mainly by seawater hydrothermal alteration. On the contrary, the discrepancy between the B concentrations in the whole rock and mineral phases (plagioclase and clinopyroxene) as well as that for Cl between single minerals could be ascribed to the occurrence of secondary phases (such as epidote and amphibole) related to hydrothermal alteration, along with the effects of fluid circulation in fracture zones.