Chemical and isotopic compositions of zircons from amphibolites of the Kamchatksky Cape Peninsula

The paper reports the first data on geochemistry and U-Pb SHRIMP geochronology of zircons from garnet amphibolites whose fragments are hosted by the sole of the ophiolite complex of the Kamchatsky Cape, eastern Kamchatka. The zircons compose homogeneous sampling, have relatively small sizes, are anhedral, have no oscillatory zoning, and possess practically no inclusions. Chemical and photoluminescent characteristics of the zircons testify to their metamorphic genesis. U-Pb SHRIMP dates of the zircons (81.4+/-9.6 Ma) indicate that metamorphism of the amphibolite complex took place in Campanian, Late Cretaceous. These dates seem to correspond to the peak of high-pressure metamorphism, which is thought to be related to origin of an ophiolite complex of the suprasubduction type and its uplift within the Kronotsky Island arc.

本论文首次报道了东堪察加堪察加角（Kamchatsky Cape）蛇绿岩套（ophiolite complex）底板所包裹的石榴子石角闪岩（garnet amphibolites）中锆石（zircon）的地球化学特征与U-Pb SHRIMP地质年代学（U-Pb SHRIMP geochronology）数据。所采集的锆石样本均一性良好，粒径相对较小，呈他形晶，无振荡环带，且几乎不含矿物包裹体。锆石的化学特征与光致发光特性证明其为变质成因。锆石的U-Pb SHRIMP定年结果为81.4±9.6 Ma，表明该角闪岩套的变质作用发生于白垩纪晚期的坎潘期（Campanian）。该定年结果与高压变质作用峰期时间吻合，而该峰期被认为与超俯冲型（suprasubduction type）蛇绿岩套的形成及其在克罗诺茨基岛弧（Kronotsky Island arc）内的抬升作用相关。