航磁在冈底斯西段地质调查中的应用分析-application and analysis of aeromagnetic technology in geological survey of the west gangdise section.docx

into two apophyses and two basins. South Gangdise magmatic belt can be independently viewed as a tectonic basin unit, including Geji apophysis, the Dongcuo-Cuoqin North basin, Nima - Lunpola basin, Nagqu apophysis, and the Xainza South basin.Bannu suture zone located in the north end of Gangdese is made up of ophiolite having a small size of anomaly, resulting in two correspondingly resembling north-south aeromagnetic anomaly zone. On the anomaly map of 10km, except that a few rocks is reflected, the vast majority of anomalies attenuate and disappear and magnetic body downward extends shallowly. Yajing suture zone, being composed of two north and south parallel anomaly belts, streches from NW-NWW in the form of linearity. A single anomaly is often in a large size and could reach length of tens of kilometers. And the inerratic linear anomalies of positive and negative peaks, having strong amplitude, constitute the Brahmaputra abnormal zone. By extending 10 km, anomaly of southern part decays faster while that of nortern part still retains linear structure.Acidic magma activities of Gangdese in Cenozonic completely record the geological configuration events of the Tethys evolution of north Bangong Lake-Nujiang and southern Yaruzampbo land and the subsequent collision and post-orogenic extensional tectonics. This kind of rocks has more transformational types and the magnetics could even turns from none to moderate scale. Generally speaking, the magnetism gradually weaken from medium to acidity. Meanwhile, the magnetic features and formation causes of acidic intrusion also have some connections. Granties emerging in Tethys swoop of early time contains more Manyuan while those of later period have weak magnetism. Volcanic rocks, including basalt, andesite and rhyolite volcanic rocks, are referred to as volcanic anomalies because of the commly existential magnetic uniformity and aslo they can not be distinguished from features of anomalies. Ordinarily, volcanic rocks o