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本文报道藏东地区晚石炭-晚二叠世古地磁研究结果,获得了3个可靠的古地磁极位置.对采自24个采点(219块灰岩、玄武岩及泥质粉砂岩)样品的系统古地磁学研究表明:晚石炭世灰岩样品中赤铁矿和磁铁矿共存,其退磁曲线具有典型的双分量特征,高温特征剩磁(ChRM)均为正极性(负倾角).中-晚二叠世灰岩、凝灰岩及玄武岩样品的主要载磁矿物为磁铁矿(部分玄武岩样品为赤铁矿),退磁曲线表现为双分量或单分量特征,其高温特征剩磁均为负极性(正倾角),可通过标准的褶皱检验,且在地层坐标系下中-晚二叠世与晚石炭世特征剩磁方向的单一极性分别与Kiaman反极性期及之前的正极性特征相吻合,应该均为岩石形成时期的原生剩磁信息.与羌北地区的古地磁结果对比可得:(1)昌都与羌北地块在晚石炭至早二叠世期间相互独立其间的北澜沧江洋盆可能于中二叠世前闭合,晚二叠-早三叠世进入陆-陆碰撞阶段.(2)羌北-昌都地块晚石炭至晚二叠世期间位于南纬中低纬度地区,早三叠世以后开始大规模北向移动,与现今位置相比运动总量达5000km以上.
This paper reports the paleoclimate study of the Late Carboniferous-Late Permian in the eastern Tibet and obtained three reliable paleomagnetic polar positions. For the system of 24 samples collected from 219 limestone, basaltic and argillaceous siltstones Paleomagnetism studies indicate that the demagnetization curves of the Late Carboniferous limestone coexist with magnetite, and the demagnetization curve has the typical two-component characteristics, and the high-temperature characteristic residual magnetism (ChRM) is positive (negative dip) The main magnetite for the Late Permian limestone, tuff and basalt samples is magnetite (some basalts are hematite), and the demagnetization curve is characterized by a two-component or a single-component feature with high remanent remanence (Positive dip), and can pass the standard fold test, and the single polarity of the remnant magnetic direction of the Middle-Late Permian and the Late Carboniferous in the stratigraphic coordinate system is similar to that of the Kiaman reverse polarity phase and the previous positive polarity phase Which are all primary remanence information during the rock formation.Compared with the paleomagnetic results in the Qiangbei area, we can get: (1) the northern Lancang Cang River between Qamdo and Qiangbei blocks during Late Carboniferous to Early Permian The oceanic basin may close before Middle Permian and late Permian - Early Triassic into the continental-continental collision stage. (2) During the Late Carboniferous to Late Permian period, the Qiangbei-Qaidam block was located in the middle and low latitudes of the southern latitude. After the Early Triassic, a large-scale northward movement began. Compared with the present Position compared to the total amount of movement up to 5000km.