Abstract The Kalgoorlie gold camp in the Yilgarn craton of Western Australia comprises the supergiant Golden Mile and the smaller Mt. Charlotte, Mt. Percy, and Hidden Secret deposits. Since the camp’s discovery in 1893, ~1,950 metric tons (t) of Au have been produced from a total estimated endowment of ~2,300 t. The camp is located within Neoarchean rocks of the Kalgoorlie terrane, within the Eastern Goldfields superterrane of the eastern Yilgarn craton. Gold mineralization is distributed along an 8- × 2-km, NNW-trending corridor, which corresponds to the Boulder Lefroy-Golden Mile fault system. The host stratigraphic sequence, dated at ca. 2710 to 2660 Ma, comprises lower ultramafic and mafic lava flow rocks, and upper felsic to intermediate volcaniclastic, epiclastic, and lava flow rocks intruded by highly differentiated dolerite sills such as the ca. 2685 Ma Golden Mile Dolerite. Multiple sets of NNW-trending, steeply dipping porphyry dikes intruded this sequence from ca. 2675 to 2640 Ma. From ca. 2685 to 2640 Ma, rocks of the Kalgoorlie gold camp were subjected to multiple deformation increments and metamorphism. Early D 1 deformation from ca. 2685 to 2675 Ma generated the Golden Mile fault and F 1 folds. Prolonged sinistral transpression from ca. 2675 to 2655 Ma produced overprinting, NNW-trending sets of D 2 -D 3 folds and faults. The last deformation stage (D 4 ; < ca. 2650 Ma) is recorded by N- to NNE-trending, dextral faults which offset earlier structures. The main mineralization type in the Golden Mile comprises Fimiston lodes: steeply dipping, WNW- to NNW-striking, gold- and telluride-bearing carbonate-quartz veins with banded, colloform, and crustiform textures surrounded by sericite-carbonate-quartz-pyrite-telluride alteration zones. These lodes were emplaced during the earlier stages of regional sinistral transpression (D 2 ) as Riedel shear-type structures. During a later stage of regional sinistral transpression (D 3 ), exceptionally high grade Oroya-type mineralization developed as shallowly plunging ore shoots with “Green Leader” quartz-sericite-carbonate-pyrite-telluride alteration typified by vanadium-bearing muscovite. In the Hidden Secret orebody, ~3 km north-northwest of the Golden Mile, lode mineralization is a silver-rich variety characterized by increased abundance of hessite and petzite and decreased abundance of calaverite. At the adjacent Mt. Charlotte deposit, the gold-, silver-, and telluride-bearing lodes become subordinate to the Mt. Charlotte-type stockwork veins. The stockwork veins occur as planar, 2- to 50-cm thick, auriferous quartz-carbonate-sulfide veins that define steeply NW- to SE-dipping and shallowly N-dipping sets broadly coeval with D 4 deformation. Despite extensive research, there is no consensus on critical features of ore formation in the camp. Models suggest either (1) distinct periods of mineralization over a protracted, ca. 2.68 to 2.64 Ga orogenic history; or (2) broadly synchronous formation of the different types of mineralization at ca. 2.64 Ga. The nature of fluids, metal sources, and mineralizing processes remain debated, with both metamorphic and magmatic models proposed. There is strong evidence for multiple gold mineralization events over the course of the ca. 2.68 to 2.64 orogenic window, differing in genesis and contributions from either magmatic or metamorphic ore-forming processes. However, reconciling these models with field relationships and available geochemical and geochronological constraints remains difficult and is the subject of ongoing research.

Abstract Extremely intimate space-time associations between caic-alkaline (shoshonitic) lamprophyres and mesothermal gold deposits are now confirmed worldwide and from Archean to Tertiary times. They include the late Archean gold deposits of the Superior province (Canada) and the Norseman-Wiluna belt (Western Australia), which hosts the world’s most golden square mile (Kalgoorlie) and almost certainly one of the richest gold deposits outside South Africa, (Porgera, Papua New Guinea). In an increasing number of areas, lamprophyres are found to be the only igneous rocks emplaced at the same time as the gold, and economic status has been found to correlate quantitatively with the presence of lamprophyres. Many lamprophyric rocks appear to be enriched in Au relative to other igneous rocks, with contents of tens of ppb Au being common. Evidence that such enrichments could be primary includes the following, although this will remain impossible to prove for lamprophyres in major gold fields: (1) the persistence of high Au contents in calc-alkaline lamprophyres which lie outside the alteration halos of large-scale gold systems (e.g., British Caledonides) and more especially in lamprophyric rocks which are not associated with gold deposits at all (e.g., lamproites); (2) the plausible explanation for Au enrichment that exists in the lamprophyres’ exceptionally deep origins in presumed Au-rich regions of the earth (>150 km), high F, K, Ba, and Rb, moderate S contents, and H 2 O/(H 2 O + CO 2 ratios, and fluidized condition, which make them uniquely similar to auriferous ore fluids in their element abundances and possibly in their physical state, and thus, well suited to transporting gold into the crust; and (3) detailed statistical analysis of Au data, notably for the Superior province, comparing fresh versus altered and proximal versus remote samples from gold mineralization to rule out any overall addition of Au to these lamprophyres from external sources. The widespread presence of lamprophyres suggests a much more significant role in gold deposition for large-scale crust-mantle events and for certain (e.g., oblique subduction) tectonic regimes than has hitherto been generally recognized. A part-genetic, part-structural interpretation is preferred, in which lamprophyres may contribute at least some Au or fluids from deep sources into mesothermal systems, which then redeposit the Au according to the metamorphic model in its broadest sense. This is in accord with stable isotope evidence, which argues against a direct relationship between lamprophyric and gold-depositing fluids but by no means precludes an indirect one.