青海茶卡北山锂稀有多金属矿床白云母^(40)Ar-^(39)Ar定年及其地质意义

^(40)Ar-^(39)Ar dating of muscovite in Chaka Beishan Li-polymetallic deposit in Qinghai province and the geological significance

宗务隆构造带南侧的成矿环境与“马尔康-雅江-喀喇昆仑巨型锂矿带”具有很大的相似性,新发现的茶卡北山伟晶岩型锂多金属矿床证实此带是青藏高原北部的一条重要的锂、铍矿成矿带,该矿床内含矿伟晶岩主要为含锂辉石花岗伟晶岩和含绿柱石白云母花岗伟晶岩,形成于晚三叠世。对含矿白云母伟晶岩进行白云母^(40)Ar-^(39)Ar同位素测年结果显示,随着温度从750℃逐渐升到1100℃,白云母^(40)Ar-^(39)Ar年龄坪非常平坦,其年龄值为210.4 Ma—212.7 Ma,坪年龄为212.60 Ma±0.64 Ma,与晚期伟晶岩结晶年龄相近,基本限定茶卡北山伟晶岩型锂稀有多金属矿床的成矿年龄为晚三叠世晚期。

The area in the south of Zonglong tectonic belt is very similar in metallogenic setting to the Markang-Yajiang-Karakoram giant Li ore belt and Chaka Beishan pegmatite type Li-poly metallic deposit is newly discovered here proving the area a new important Li-Be mineralization belt in the North of Qinghai-Tibet plateau.The Late Trassic spodumene-bearing granitic pegmatite and the beryl-bearing muscovite granitic pegmatite are mainly the ore hosts.^(40)Ar-^(39)Ar dating of muscovite from the muscovite granitic pegmatite shows that at the temerature rising from 750℃to 1100℃the age plateau of the muscovite get very flat.The age value is 210.4 Ma-212.7 Ma and the plateau age 212.60 Ma±0.64 Ma,very close to that of crystallization of the pegmatite corresponding the Late Triassic.