Iron Oxide Cu-Au Monograph - Volume 4, Abstract

The Aldan Shield, part of the Siberian Craton, incorporates numerous iron oxide, copper, gold and uranium deposits formed during the Palaeoproterozoic and Mesozoic. These deposits are clustered within mineralised districts, and along major crustal lineaments across the shield, and include those with combinations of two or more of these metals. The period from 2.0 to 1.8 Ga during the Palaeoproterozoic, was especially productive for IOCG related apatite-iron oxide-REE, iron oxide [±apatite±copper] and copper-iron oxide-gold deposits, while evidence for the presence of significant contemporaneous Au and U mineralisation is growing. These deposits are hosted by the Archaean-Palaeoproterozoic cratonic basement, with no direct relationship to the significant contemporaneous anorogenic Palaeoproterozoic A-type igneous suites of the region. In contrast, during the Mesozoic, particularly from 150 to 130 Ma, major uranium and gold, and low grade copper concentrations were formed, but apparently only minor Fe oxide and no significant IOCG related mineralisation. These younger deposits are mostly hosted in the Cambrian cratonic cover and/or along the cratonic basement/cover unconformity, and are closely associated with, or hosted by, small intrusives of potassic alkaline and alkalic (with shoshonitic affinities) to calc-alkaline rocks exhibiting similarities with those of both distal subduction-related and anorogenic igneous suites. The Palaeoproterozoic and Mesozoic deposits represent two temporally separated ore deposit assemblages involving copper, gold, iron oxides and uranium developed within similar, but not identical cratonic tectonic settings, and possibly with common metal sources in the lower crust. The older group included the development of IOCG mineralisation, the younger apparently did not, corresponding rather to alkalic porphyry/epithermal deposit style.