ROCK-MAGNETIC PROPERTIES OF THE POINT BAR DEPOSITS IN THE UPPER MAINSTREAM OF MINJIANG RIVER AND THEIR ORIGIN

The Magnetic properties measured from 21 recent sediments on the upper reaches of the Minjiang River (source of the Minjiang River to the Zipingpu reservoir) show that:(1) the sediments are primarily composed of ferrimagnetic magnetite, and contain a certain amount of siderite and a small amount of hematite. siderite in the source of the Minjiang River is relatively high; (2) minerals of pseudo single domain (PSD) to multi domain (MD) dominate the magnetic minerals; (3) concerning the spatial distribution of magnetic minerals, magnetic minerals on the reach between Maoxian to the Zipingpu reservoir are higher than those in the reach between source of Minjiang River to Maoxian, showing a trend of gradually increasing, and the former is relatively coarser. (4) tributaries of the Minjiang River, the landslide on both sides and the hydrodynamic variation along the river are the main factors which influence the magnetic characteristics of these sediments in the mainstream of the Minjiang River.