Research On Paleomagnetism Of The Devonian In The Lhasa Plate

Lhasa Lhasa block is located in a landmass between bangonghu-dingqing suture zone and Brahmaputra suture zone, and the paleomagnetism data of devonian is shorted. In the paper, the paleomagnetism datas of devonian daerdong group and chaguoluoma group in lhasa block were studied and analysed, meanwhile tectonic evolution characteristics was discussed.The profile with good continuity selected in the paper is located20kilometer to northern shenzha county. Reasonable method was used to mine40samples crossing5mining points in daerdong group and37samples in chaguoluoma group. Research indoor was based on the best laboratory in the country, while the most advanced technology and method of data analysis at the international level were adopted.Most of the77samples from8mining points in shenzha of devonian were demagnetized by thermal demagnetization and the other of that were demagnetized with alternating demagnetization. Most samples reflected characteristics of double components and a small part with single component, three components or multi-components. Low temperature remanent magnetism components were obtained through Fisher statisyics, which was close to present direction of geomagnetic field. Thus we can infer that samples sample may be affected by the modern geomagnetic field, which should be the viscous remanent magnetism. Results show that most samples were isolated high temperature components but not pass the fold test, so reliable information of high temperature remanent magnetism could’t be gotten. That mainly because devonian is so distant that the samples have been affected by long-term tectonic activity, metamorphic deformation and the late geomagnetic field. So it is difficult to obtain the reliable paleomagnetic pole and careful to reference predecessors’ research results.