The North Queensland, Australia Ernest Henry Iron Oxide Type Copper Gold (iocg) Deposit In Physical And Chemical Characteristics And Trace Element Geochemical Characteristics - Magnetite Revelation About The Formation Of Global Iocg Deposits

The aims of this work are to investigate the formation of Ernest Henry IOCG and to understand the ore-forming process of Ernest Henry IOCG deposit by using trace element geochemistry of specific mineral and study on the physical and chemical characteristics of Ernest Henry IOCG deposit. SEM-CL is employed to investigate the characteristics of Quartz from a wide range of geological setting in Ernest Henry IOCG deposit. LA ICP-MS are used to determine the trace element concentration of both magnetite and related sulfides from Ernest Henry deposit and barren ironstone from regional area. Elemental mapping analysis on magnetite and sulfides were carried on the electron microprobe.electron microprobe coupled with a XCL were applied to investigate the trace element distribution in K-feldspar from the variety breccias within and around the Ernest Henry orebody.Ernest Henry, the second largest IOCG deposit after Olympic Dam and Third largest Cu producer in Australia, is a typical IOCG deposit. The physical and chemical characteristic is important components to recognize this deposit. Before the study, an extremely detailed review of the development of global IOCG and minerals discussed in this work were summarized in Chapter Ⅱ and Chapter Ⅲ. Ore body at Ernest Henry is hosted by meta-volcanic rocks which comprise a multiple-components such as clasts, matrix and infill and lies in a very large brecciated system. Two types of breccias are identified at Ernest Henry deposit. There is a clear relationship between grade and breccia characteristic. The Cu-Au mineralization at Ernest Henry IOCG is intimately associated with the brecciation and consists of multiple hydrothermal activities and involved in at least two different ore-forming fluids (magmatic fluids and basinal fluids) in the formation of Ernest Henry orebody. Earlier Na-Ca alteration are perversely spread in the Eastern Succession of Mount Isa Inlier, especially play an vital roles at Ernest Henry, which are overprinted by the later K-Mn-Fe-(Ba) alteration and Cu-Au mineralization.Quartz trace element and cathodoluminescence characteristics and feldspar cathodoluminescence also showing a very complex ore-forming components and process, for examples, in K-feldspar from the shallow part of the orebody, socid alteration are very strong, and the barium are more intensity with the latest carbonate flooding race element distribution in magnetite and pyrite are useful tool to distinguish the mineralized orebody from the regional unmineralized or barren mineralized ironstone at Ernest Henry IOCG deposit. The metal distribution along the downhole depth is studies as well in this study. At the end of chapter V, the source of metal, the source of ore-forming fluids, the temperature,pressure and other chemical-physical control on the ore-forming process of Ernest Henry IOCG deposit are discussed, and a potential ore forming models are presented.Trace element concentration and distribution of magnetite plays a vital role in mineral exploration using minerals as an indicator. We use EMPA and LA ICP-MS to mapping and analysis the trace element of magnetite from Eastern Succession of Mount Isa Inlier, especially concentrated on the magnetite from Ernest Henry IOCG deposit. Electron microprobe trace element mapping analysis indicates that magnetite is not zoned with respect to trace element distribution. High Mn/Ti ratios can be used to distinguish Ernest Henry and other regional Eastern Succession of Mount Isa Inlier IOCGs from unmineralized magnetite-rich breccia bodies in the region. Magnetite compositions vary widely across the deposit and most trace elements vary over two to three orders of magnitude among samples or even among grains within a single sample. In all48samples where large variations in magnetite trace element concentration exist among grains, petrography shows that the magnetite can be distinguished an may belong to a different paragenetic stage or multiple grains of the same paragenetic stage may have been affected by different post-precipitation processes. The trace element variations are not associated with location within the deposit, paragenesis, rock types and ore grade, but are controlled by many local factors such as the degree of crystallization; the degree of deformation; post-precipitation oxidation to hematite; the abundance of associated sulphides; the origin of the magnetite as infill or replacement of wall rock. The control factor of trace element in magnetite likely reflects a complex combination of fluid composition, temperature, redox conditions, and fluid rock interaction. Magnetite in IOCGs from different geological setting have markedly different trace element signatures.we really do not know what kind of factor have a impact on the trace element of magnetite although we know many factors.In addition, a set of procedure of analyzing the trace element and rare earth element in minerals (in this section, mainly focused on the magnetite and sulfides) have been made better.