Behavior of incompatible elements in rock-forming minerals under high temperature and high pressure

为了阐明高温高压条件下造岩矿物中不相容微量元素的地球化学和岩石学行为，我们测定了3000多具代表性的晚第三纪—第四纪火山岩及其上地幔和下地壳捕虏体的主微量元素及其主要组成矿物。澄清了以下几个重要的结果和结论：日本东北部和伊竹-马里亚纳弧的火山岩均表现为岩石/原始地幔不相容归一化模式的典型岛弧，具有显著的正Ba、K、Sr异常和负Nb异常。虽然沿日本西南弧火山锋的火山岩与扇纳火山锋的火山岩具有相同的特征，但碱系向大陆方向由岛弧向大陆模式转变。大陆、大洋岛屿和岛弧的上地幔黑橄榄岩捕虏体及其组成矿物（长辉石、顽辉石、铬透辉石、铬尖晶石或铬铁）中不相容元素的浓度通常低于检出限。因此，很难认为玄武岩岩浆中不相容元素的来源是这些辉橄榄岩捕虏体。日本列岛下地壳捕虏体及其必需矿物的归一化模式和稳定同位素比值与钙-cl-碱性火山岩的归一化模式和稳定同位素比值相似，表明其为积云成因。此外，根据Rb-Sr年龄定年，铁质捕虏体属于前寒武纪。

In order to elucidate the geochemical and petrological behavior of incompatible trace elements in rock-foming minerals under the high temperature and high pressure conditions, we have determined major and trace elements of about 3000 representative late Tertiary-Quaternary volcanic rocks and their xenoliths derived from upper mantle and lower crust together with their major constituent minerals. The following several important results and conclusions have been clarified;1. All of the volcanic rocks in northeast Japan and Izu-Mariana arcs show the typical island arc of the rock/primitive mantle normalized pattern for incompatible trace elements, having the remarkable positive Ba, K and Sr anomalies and the negative Nb anomaly. Although, the volcanic rocks along the volcanic front in southwest Japan arc have the same characteristics as theose of the fanner, alkali series hange from island arc to continental patterns towards the continents.2. Concentration if incompatible elements in upper mantle iherzolite xenoliths in continents, oceanic islands and island arcs and their constituent minerals, forsterite, enstatite, chromian diopside and chromian spinel or pyrope is usually below the detection limit. Accordingly, it is very difficult to consider that the source materials of incompatible elements in basaltic magams are of these lherzolite xenoliths.3. Normalized patterns and stable isotope ratios of lower crustal xenoliths in Japanese Islands and their essential minerals are Similar to those of calc-cl-lkaline volcanic rocks, indicating the cumulus origin. Besides, the mafic xenoliths from Itinome-gata suggest the pre-Cambrian age by the Rb-Sr age dating.