The Comparative Study Of Hillside And Olympic Dam Iron Oxide-copper-gold Deposit,South Australia

Hillside Cu-Au deposit and Olympic Dam Cu-Au-U-REE deposit are both located in Olympic Cu-Au province, within the eastern Gawler craton. The former lies in the south while the latter in the north. The Mesoproterozoic transition in the Gawler craton appears from active plate margin setting to a continental interior setting. Coincidently, the Gawler Range Volcanics-Hiltaba Suite magmatic event was happening, which resulted in formation of extensive intrusions and volcanics associated with metallogenic acitivity throughout the Gawler craton.This paper focuses on the Hillside Cu-Au deposit and Olympic Dam Cu-Au-U-REE deposit, comparing them between metallogenic conditions, features of mineralization and alteration and geochemics to eastablish the model of genesis for each of them.Hillside Cu-Au deposit is located within the N-S strinking fault, strictly controlled by the minor faults. The deposit is hosted by Mesoproterozoic Moonta-Wallaroo group which consist of a series of metapsammite and metavolcanics and carbonates. The ore-bearing intrusions are syenogranite and gabbro. The orebody are mainly tubular type. On the other hand, The Olympic Dam Cu-Au-U-REE deposit is confined to a fault-bounded graben in continental rift. The host rock of the deposit are Olympic Dam formation and Greenfield formation which are composed of a variety of granite breccias. Three igneous rock are defined: alkaline granite, diabase and felsic volcanic. The deposit contain two types of mineralization—a strata-bound type and a transgressive type. Two deposit share the similar metal mineral assemblages, such as hematite, magnetite, chalcopyrite, pyrite, gold and rare-earth mineals. However, Olympic Dam deposit developed large-scale U mineralization. In terms of alteration, Hillside deposit mainly developed skarnization and potash alteration. While Olympic Dam deposit mainly mainly developed serictie, silicification and carbonation. Large-scale magnetite and hematite mineralization occurred and the phenomenon that magnetite was metamorphismed by hematite can be also observed in both district. All the features indicate the differences of metallogenic conditions and process of formation between two deposit.Geochemical features show that the syenogranite and gabbro in Hillside district are evolved from the same mantle-derived magma, developing in the intraplate environment. Similarly, granite in Olympic Dam district has the same fearutes with intrusions in Hillside district, which suggest that they were evolved from regional Hiltaba suite. Besides, through the studying of trace element and REE, metal source are main from magma and the host rock are minor. But Olympic Dam deposit is opposite to Hillsde deposit, metal source are mainly from host rock.The age of two deposit are almostly same, 1590 Ma, coincident with Mesoproterozoic Gawler Range volcanics-Hiltaba suite event. This indicate that the genisis of two deposit is closely correlated with this event.Comparing the metallogenic conditions and geochemical features between two deposit and the constraint of age, this paper preliminarily define the Olympic Dam deposit is fluid overprinting model, and Hillside deposit is metasomatic model.