Литосфера (Aug 2016)
Composition, structure and fluid regime of differentiated porphyritic intrusion Magnitogorsk iron-ore deposit (Southern Urals)
Abstract
Case study of the differentiated subvolcanic porphyritic intrusion underlying Magnitogorsk skarn-magnetite deposit revealed regular relations between petrochemistry features of the rocks and composition of halogens (Cl and F) in the accessory apatite. During the process of intrusion formation in terms of general trend of differentiation from the pyroxene-porphyrites its base to atachites (trachyandesites, phonotephrites) its upper part, several autonomous fluid-magmatic systems (FMS), which differ in major and trace elements distribution as well as halogen composition in apatites, are formed. In the uppermost part of the atachite section, mostly saturated by alkalis and volatile components, through a further fluid-magmatic stratification were formed two atachite strata: sodium, enriched in Na, Ca, Sr, and with a higher Cl content in apatite and potassium “ore-bearing” located at a higher hypsometric level and enriched in K, Rb, Fe, V, Ti, P, with a higher content of F in apatite. Formation of subvolcanic intrusion was accompanied by repeated occurrences of explosive phenomena. These data indicate the features of magmatism in Magnitogorsk megazone in D3-C1, at the change the island-arc stage by accretionary-collision (island arc-continent) one
