内蒙古狼山左行走滑韧性剪切带变形特征、时间及意义

发布时间：2018-07-03 18:27

本文选题：狼山 + 左行走滑韧性剪切带　；参考：《地学前缘》2017年03期

【摘要】：华北克拉通北缘渣尔泰-白云鄂博-化德元古宙裂谷带,是一条重要的成矿带,发育一系列大型、超大型矿床。裂谷带自西向东分别沉积了中元古代渣尔泰群、白云鄂博群和化德群。最近的研究表明,分布在狼山地区的渣尔泰群中火山岩夹层锆石U-Pb年龄及碎屑锆石年龄将其时代限定为新元古代,而渣尔泰山一带的渣尔泰群碎屑锆石年龄最小峰值大于1 700 Ma,二者很可能不是同一套地层。前者被从原渣尔泰群中解体出来,称为狼山群。但由于狼山群与渣尔泰群岩石组合的相似性,以及地层展布在区域走向上相连,特别是它们都是华北北缘重要的含矿层,矿化特征也具相似性,导致目前为止这两套地层的叠置关系还不清楚,这对于认识华北北缘中新元古代裂谷发育特征和演化,以及对认识相关矿化规律造成了一定的混乱和难度。本文对发育于狼山地区平行山体走向的韧性剪切变形带进行了研究。结果表明狼山韧性剪切带内变形岩石糜棱面理走向NE-SW,向NW或SE陡倾,矿物拉伸线理向SW或NE缓倾,野外及显微运动学标志显示为左行走滑韧性剪切带。剪切带内两个糜棱岩化云母石英片岩样品中变形白云母的40Ar/39Ar坪年龄分别为(356.7±2.5)Ma和(379±4.7)Ma,表明剪切带形成于晚泥盆世。狼山韧性剪切带很可能是古亚洲洋闭合过程中导致阿拉善地块与鄂尔多斯地块发生相对滑动所形成的。该剪切带晚泥盆世的左行走滑导致新元古代狼山群和中元古代渣尔泰群叠置到一起。因此,在渣尔泰山北侧和狼山南部及阿拉善块体北缘的覆盖层之下,很可能分别存在隐伏的新元古代成矿带和中元古代成矿带。
[Abstract]:The Jar Tai-Baiyun Obo-Huade Proterozoic rift belt in the northern margin of North China Craton is an important metallogenic belt with a series of large and super-large deposits. From west to east, the rift zone has deposited the Middle Proterozoic Jar Tai Group, Bayan Obo Group and Huade Group respectively. Recent studies show that the zircon U-Pb age and the clastic zircon age of the volcanic intercalation in the Jar Tai group in the Langshan area limit its age to Neoproterozoic. However, the minimum zircon age of the Jar Tai Group in the Jar Taishan area is more than 1 700 Ma, which is probably not the same set of strata. The former is disintegrated from the original Jar Tai group, known as the Langshan Group. However, because of the similarity between the rock assemblages of Langshan Group and Jar Tai Group, as well as the distribution of strata in the regional strike, especially because they are important ore-bearing beds in the northern margin of North China, the mineralized characteristics are also similar. So far, the overlay relationship between the two sets of strata has not been clear, which has caused some confusion and difficulty in understanding the developmental characteristics and evolution of the Mesoproterozoic rift in the northern margin of North China, as well as in the understanding of the related mineralization laws. The ductile shear deformation zone of parallel mountain strike in Langshan area has been studied in this paper. The results show that the metamorphic rocks in the Langshan ductile shear zone tend to NE-SW-SWand to NW or SE steep dip, mineral stretching line to SW or NE gentle dip, field and micro-kinematics show that the left strike-slip ductile shear zone. The 40Ar/39Ar plateau ages of deformed Muscovite in two mylonized mica quartz schist samples in the shear zone are (356.7 卤2. 5) Ma and (379 卤4. 7) Ma, respectively, indicating that the shear zone was formed in the late Devonian. The Langshan ductile shear zone is probably formed by the relative sliding between the Alashan and Ordos blocks during the closure of the Paleo-Asian Ocean. The late Devonian left strike-slip of the shear zone resulted in the superposition of the Neoproterozoic Langshan Group and the Middle Proterozoic Jar'tai Group. Therefore, it is very likely that there are concealed Neoproterozoic metallogenic belts and Mesoproterozoic metallogenic belts under the overburden of the north side of Jar Tai Mountain and the south of Langshan Mountain and the northern margin of Alashan block.
【作者单位】：中国地质科学院地质力学研究所;中国地质科学院矿产资源研究所;昆明理工大学;
【基金】：中国地质科学院地质力学研究所基本科研业务费项目(DZLXJK201502) 国家自然科学基金项目(41472211,41502199)
【分类号】：P542

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