Magnetic fabric constraint on tectonic setting of Paleoproterozoic dyke swarms in the North China Craton, China

Abstract Locating the magma source for the mafic dyke swarms in the North China Craton (NCC) is important for evaluating tectonic setting and emplacement mechanism. Here we have conducted systematic AMS studies on Paleoproterozoic dykes from the Fengzhen, Fuping and Lvliang areas of the NCC. Rock magnetic analyses indicate that PSD magnetite is the predominant magnetic carrier although the Lvliang dykes contain more SD magnetic grains than the Fengzhen and Fuping dykes. The Fengzhen and Fuping dykes have mostly normal AMS fabrics whilst the Lvliang dykes exhibit a larger proportion of intermediate AMS fabrics. Most of the Fuping dykes are found to have intruded sub-vertically upward although some fabrics indicate northward magma flow from imbrication and the distribution of K 1 AMS axes. The Lvliang dykes identify a southwestward magma flow from opposed imbrications and distributions of K 1 AMS axes. The Fuping area is thus interpreted to have been located near to the magma source which fed most dykes in the central NCC. A variety of magma sources are suggested for dykes in other parts of the NCC. Dykes near the southern margin of the craton probably resulted from lateral migration of magma from the Xiong’er source and contrast with the dykes in the central NCC fed by the Fuping magma source. Further Paleoproterozoic magma sources likely remain to be identified.