内蒙古海苏沟多金属矿田成矿模式与找矿前景

海苏沟多金属矿田是黄岗—甘珠尔庙锡多金属成矿带的重要组成部分。海苏沟多金属矿田位于浩尔吐—小井子复背斜的核部,岩浆活动强烈,包括铜钼矿床2处、铅锌银矿床3处,但相关地质研究程度较低。该区矿化类型包括热液石英脉型铜钼矿化、浸染状钼矿化、矽卡岩型铅锌矿化、热液脉型铅锌银矿化、云英岩型锡矿化、矽卡岩型锡矿化等;蚀变以矽卡岩化、褐铁矿化、硅化为主,次为云英岩化、磁铁矿化、黄铁矿化、孔雀石化等。文章在野外一线观察的基础上,总结了矿田控矿特征,分析了成矿期次,建立了矿田岩浆热液成矿模式,并指明了矿田找矿方向和找矿前景。

内蒙古海苏沟岩体中钼矿床成岩成矿年代学、地球化学及地质意义

海苏沟岩体位于大兴安岭造山带南段,岩体中发育有海苏沟钼矿床及小井子北铜钼矿床,目前对该岩体的了解还不完善,成因类型存在争议且对两个钼矿床间差异并未进行探讨.对该岩体不同岩相花岗岩开展锆石U-Pb年代学、岩石地球化学研究,对矿区内辉钼矿进行Re-Os同位素研究.获得海苏沟钼矿床黑云母花岗岩年龄结果为137.1±0.6 Ma和143.6±0.8 Ma,测得Re-Os模式年龄为143.9±2.9 Ma.小井子北铜钼矿区二长花岗岩年龄为126.5±0.7 Ma.海苏沟岩体中花岗岩均属高钾钙碱性系列I型花岗岩,具准铝质-弱过铝质特征,主量元素SiO2含量为68.81%~77.18%,K2O+Na2O含量为6.80%~8.31%,CaO含量为0.43%~2.88%,MgO含量为0.15%~1.32%,A/CNK值介于0.97~1.07.岩石相对富集轻稀土,(La/Yb)N=6.19~10.74,稀土配分呈右倾海鸥型,具有中等铕负异常(δEu=0.37~0.81).结合已有的研究结果,认为海苏沟岩体演化过程中经历了强烈的分离结晶作用,该岩体黑云母花岗岩与钼矿床的形成密切相关.海苏沟岩体的成岩及钼成矿作用的时间与西拉沐伦成矿带的第3期大规模成岩成矿作用时间相吻合,对应当时的构造背景为构造体系转折(由挤压环境转变为拉伸环境)至岩石圈减薄的环境.

A Discovery of Anomozamites with Reproductive Organs

Anomozamites haifanggouensis (Kimura et al.) Zheng et Zhang comb. nov. is a characteristic Bennettitalean plant in Middle Jurassic flora. Only one specimen was collected from Haifanggou Formation (Middle Jurassic) in Daohugou village, Shantou town, Ningcheng County, Nei Mongol Autonomous Region, China. The stem of plant is slender and repeatedly branches as a dichasial system with a fertile shoot in the fork, forming equal and widely divergent branches, on the branches born with the fronds of Anomozamites type. Its reproductive organs consists of some microsporophylls and a few of the bracteoid small leaves (or receptacular leaves). Some scattered bracteoid leaves and microsporophylls were formerly considered by Pan as dicots. Since then, they were proposed to be a non-committal genus Pankuangia and described them as P. haifanggouensis by Kimura et al. In this study, we discover that these bracteoid small leaves and microsporophylls should be of Anomozamites. This discovery provides strong evidence for the 'Pankuangia' determination of the taxonomical position.