内蒙古道郞和都格矿区电气石期次及硼同位素特征

Main Stages and Characteristics of Boron Isotope in Tourmaline in Daolangheduge Block, Inner Mongolia, Northern of China

内蒙古镶黄旗道郎和都格矿区位于华北地块北缘与西伯利亚板块南缘,在成矿带上属于温都尔庙–白乃庙成矿带东段。矿区地表岩体与石英脉中广泛发育电气石化矿物,且至少可分为早、晚两期。早期电气石,棕色–褐色,结晶较好,呈柱状晶形;晚期电气石,深蓝–墨绿色,结晶较差。区内电气石常出现特征的核–边结构。其硼同位素组成大部分落在与花岗岩有关的范围内,少量样品富集11B,推测可能与岩浆去气作用有关,该去气假设也得到C、H、O稳定同位素及其组成特征的佐证。

Daolangheduge district is located in northern margin of North China Plate, and in the southern margin of Siberia plate as well. Regionally, it belongs to east part of Ondor Sum-Bainaimiao me-tallogenic belt. Rich tourmaline zoning was found in this district. The tourmaline in Daolanghe-duge district could be classified into two stages. The earlier stage tourmaline, in brown-brown color, crystallization in columnar shape, is good. While later stage tourmaline, deep blue-blackish green color, with poorer crystallization extent. With regarding to boron isotopes in tourmaline, most of them are same as that of granite, closely related to hydro-fluid process, with a small amount samples enrich heavy boron isotopes, it is postulated that magma degassing cause later stage tourmaline rich in 11B. Magma degassing hypothesis is also supported by C, H, O stable isotopes and their composition.