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云南省老君山矿集区产出南秧田、花石头、茶叶山等众多钨矿床,是南岭成矿带西段为数不多的以钨为主的矿集区.由于受到多期构造热事件的影响,该矿集区的成矿年龄存在较大的争议.为此,选择白钨矿Sm-Nd同位素体系测定了南秧田钨矿田中长石石英脉型矿体的年龄,用白云母和黑云母Ar-Ar方法厘定了区域花岗伟晶岩的形成时代及其变质围岩的变质时限.研究表明,南秧田钨矿田中长石石英脉型白钨矿矿体的形成年龄为159±14Ma,明显晚于印支期形成的矽卡岩型矿体;两花岗伟晶岩及其围岩变质作用的时代分别为144~141Ma和121~112Ma,说明老君山矿集区存在晚侏罗世-早白垩世的构造热事件和成矿作用.综合前人的研究成果,老君山矿集区受到区域花岗片麻岩和花岗岩产出特征的制约,成矿时代分布与南岭成矿带一致,存在晚三叠世、晚侏罗世-早白垩世和晚白垩世3个成矿高峰期.而且,老君山矿集区的成矿特点与南岭东段的钨矿床有一定的可类比性,是“东钨西扩”的典型实例,这可能与老君山矿集区遭受了较高的剥蚀程度有关,暗示南岭西段的高剥蚀区是寻找晚侏罗世钨矿床的远景区.
The Laojunshan ore district in Yunnan Province produces a large number of tungsten-bearing ore deposits in the southern part of the Nanling metallogenic belt, such as Nanyangtian, Huashitou and Tea Hill, etc. Due to the multi-stage tectonic thermal event The age of mineralization in this ore district is quite controversial.For this purpose, the Sm-Nd isotope system of scheelite was used to determine the age of the feldspathic quartz vein type ore body in the southern seedling tungsten orefield, The biotite Ar-Ar method determined the formation age of the regional granitic pegmatites and the metamorphic time limit of the metamorphic rocks.The results show that the formation age of the olivine scheelite type scheelite in the Nanyatian tungsten ore field is 159 ± 14Ma, which was obviously later than that of Indosinian. The age of two granitic pegmatites and their surrounding rocks are 144 ~ 141Ma and 121 ~ 112Ma, respectively, indicating that there are Late Jujitsu Early Cretaceous tectono-thermal event and metallogeny.According to the previous research results, the Laojunshan ore district is restricted by the regional granite gneiss and granite output characteristics, and the distribution of mineralization age and Nanlingcheng The ore belts are consistent with the Late Triassic, Late Jurassic, Early Cretaceous and Late Cretaceous mineralization high In addition, the mineralization characteristics of the Laojunshan ore district are similar to the tungsten deposits in the eastern Nanling area, and are typical examples of “East Tungsten West Expansion”, which may be related to the Laojunshan Mining Area Suffered a higher degree of denudation, suggesting that the high denudation zone in the western section of Nanling is a long-term prospect for searching for Late Jurassic tungsten deposits.