Abstract

The paper presents data of U–Pb (ID-TIMS) geochronologic studies of schorlomite–morimotoite–andradite garnet from the Vuoriyarvi, Sallanlatva, and Salmagorsky massifs in the Kola alkaline province. The garnet is relatively rich in U (5–9 ppm) and poor in common Pb (Pb_c/Pb_t = 0.2–0.7), contains U as an isomorphous component, and does not host inclusions of any U-bearing minerals. The U–Pb ages of garnet from the various rocks of the massifs (373 ± 2 to 377 ± 1 Ma) are mutually consistent and correspond to the main pulse of alkaline ultramafic magmatism in the Kola province (360–380 Ma). The geochronologic data indicate that the U–Pb system of schorlomite–morimotoite–andradite garnet is stable and can be utilized as a reliable geochronometer for alkaline ultramafic rocks.

中文翻译：

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钙石榴石是可乐岩浆省超镁铁质碱性岩侵入年龄信息的来源

摘要

本文介绍了可乐碱矿，Vuoriyarvi，Sallanlatva和Salmagorsky断块的钙镁矿-闪锌矿-变质红榴石石榴石的U-Pb（ID-TIMS）地质年代学数据。石榴石的U含量相对较高（5–9 ppm），而普通Pb含量较差（Pb _c / Pb _t = 0.2–0.7），含有U作为同构成分，并且不包含任何含U元素的矿物。地块各种岩石的石榴石的U–Pb年龄（373±2至377±1 Ma）是相互一致的，并且对应于可拉省碱性超镁铁质岩浆作用的主要脉冲（360–380 Ma）。地质年代学数据表明，钙锰矿-榴辉石-闪锌矿-变质闪石-红闪石石榴石的U-Pb体系是稳定的，可以用作碱性超镁铁质岩石的可靠地球钟。