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• Four magmatic and associated metallogenic episodes can be defined. The metallogenic episodes are defined in four geographically distinct regions, the Pontides in the north, the western Anatolia province in the west, central Anatolian Crystalline Complex, and the Southeastern Anatolian Orogenic Belt in the east central part of Turkey are; late Cretaceous (∼88–76 Ma), latest Paleocene to early-middle Eocene (58–39.5 Ma); Oligocene-Miocene (30–18 Ma); Middle-late Miocene (16–8 Ma). • Late Cretaceous rocks have typical arc magma compositions except the Central Anatolian Crystalline complex, whereas Eocene to Miocene collisional to post-collisional rocks have compositions characteristic of arc magmas that over time interacted and assimilated by ancient crust and evolved toward slightly higher Sr/Y and La/Yb trace element characteristics reflecting the hydrous and oxidized nature of the magmas. • The late Cretaceous porphyry systems are common in the Pontides and the Central Anatolian Complex. The porphyry systems at the Pontides form a portion of a belt of porphyry Cu deposits that included world-class deposits in Serbia and Bulgaria, and extend eastward into the Caucasus of Georgia, Armenia and Iran. • Eocene porphyry systems in Turkey are the most common in Pontides, western Anatolia and southeastern Anatolian orogenic belt. Oligocene and Miocene porphyry systems are common in the adjoining countries in the Balkans and Iran, but are only known in the western Anatolia region of Turkey. • Overall, the distribution of porphyry Cu systems reflects complex plate interactions involving subduction, collision of continental blocks, closure of small oceanic basins, and rapidly shifting axes of magmatic activity. Continental collision between Eurasia and Afro-Arabia in Turkey along the Pontide subduction zone, İzmir-Erzincan-Ankara suture zone, Bitlis-Zagros suture zone, and Aegean subduction zone generated a fertile metallogenic environment with calc-alkalic and alkalic porphyry Cu (-Mo-Au) and magmatic hydrothermal systems emplaced in narrow arc segments over limited time durations within major magmatic events in the late Cretaceous to late Miocene. The major magmatic events represent multiple subduction zones that gradually stepped from north to south as small oceans closed during collisional events and the trench retreated or shifted southward as a result. Based on geological, new geochemical, and 40Ar/39Ar, U-Pb LA-ICP-MS geochronological data presented herein along with published data for igneous and hydrothermally altered rocks, four metallogenic episodes are defined; late Cretacecous, early-late Eocene, late Oligocene- early Miocene, and middle-late Miocene, in four geographically distinct regions, the Pontides in the north, the western Anatolian province in the west, central Anatolian Crystalline Complex, and the Southeastern Anatolian Orogenic Belt in the east central part of Turkey. Within those regions, porphyry Cu and intrusion-related hydrothermal systems begin in the late Cretaceous to the north, and generally young southward. They begin as porphyry Cu-Mo type, and tend to be more Au-rich from late Cretaceous to late Miocene. Published and new ages indicate early-late Cretaceous magmatic rocks in the Pontides were emplaced between ca. 131 and 65 Ma, peaking between ca. 88–76 Ma. Apart from the Re-Os molybdenite ages, published and new ages for porphyry Cu-related rocks and hydrothermal minerals from the Ayder, Konak, Esendal, Börekli, and Dereköy prospects indicate porphyry Cu formation near the end of that magmatic event (ca. 83–76 Ma). Published data indicate a somewhat shorter late Cretaceous magmatic event (86.5 to 70.3 Ma) peaking at ca. 86 to 80 Ma at the southeastern Anatolian orogenic belt with porphyry Cu systems reported to have formed contemporaneously. The latest Paleocene to early-late Eocene magmatism and porphyry-style hydrothermal systems are common across Turkey, with porphyry Cu systems formed in the eastern Pontides (58–37.9 Ma) based on the ages of their host rocks and syn -mineral stocks; in the western Anatolian province in the Tavşanlı porphyry belt (ca. 49.1–46.7 Ma) and the Biga porphyry belt (40.1–39.5 Ma), and in the Southeastern Anatolian orogenic belt (ca. 47 to 43 Ma). Oligocene-Miocene magmatism (30–18 Ma) and associated hydrothermal systems dominate during ca. 27.4 to 24.8 Ma the western Anatolian province in the Biga porphyry belt, but appear less common in other parts of Turkey except for the Cevizlidere porphyry deposit in the Southeastern Anatolian orogenic belt. Middle-late Miocene magmatism (ca. 16–8 Ma) and associated porphyry Cu systems predominate within the Afyon-Konya porphyry belt in western Anatolia, and contains the youngest porphyry related magmatic and hydrothermal systems (14.4–8.9 Ma). Calc-alkalic porphyry Cu ± Mo-Au systems dominate all belts except the Afyon-Konya porphyry belt where alkalic porphyry Au-Cu systems are present. The porphyry systems are dominantly metaluminous and medium to high-K rocks with a range in composition from diorite to granite, with monzonite and syenite associated with the alkalic porphyry systems. Late Cretaceous rocks have typical arc magma compositions except the Central Anatolian Crystalline complex, whereas Eocene to Miocene collisional to post-collisional rocks have compositional characteristic of arc magmas that over time interacted and assimilated by ancient crust and evolved toward slightly higher Sr/Y and La/Yb trace element characteristics. The trace element compositions along with rare earth element patterns share characterristics, typical of rocks associated with porphyry Cu-related magmas reflecting the hydrous and oxidized nature of the magmas. The late Cretaceous porphyry systems common in the Pontides form a portion of a belt of porphyry Cu deposits that included world-class deposits in Serbia and Bulgaria, and extend eastward into the Caucasus of Georgia, Armenia and Iran. Early-late Eocene porphyry systems in Pontides, western Anatolian province and southeastern Anatolian orogenic belt form clusters not extending the in the Balkans. Oligocene and Miocene porphyry systems are common in the adjoining countries in the Balkans and Iran, but are only known in the western Anatolia region of Turkey. Overall, the distribution of porphyry Cu systems reflects complex plate interactions involving subduction, collision of continental blocks, closure of small oceanic basins, and rapidly shifting axes of magmatic activity. [ABSTRACT FROM AUTHOR]

Field relationships and U-Pb data (zircon) are used to constrain the timing of tectonomaginatic events that occurred shortly after the formation of Late Devonian (~372 Ma) porphyry Cu-Au deposits at Oyu Tolgoi (Mongolia). In tire two northernmost of the several discrete porphyry centers (Hugo Dummett deposits), Upper Devonian rocks positioned stratigraphically above copper-gold mineralization preserve a record of uplift, exhumation, and subsequent burial shortly after mineralization. Strongly altered and mineralized quartz mon-zodiorite and volcanic rocks at Hugo Dummett are overlain by an unmineralized dacite sequence (369 ± 2 Ma). The basal breccia and conglomerate of the dacite sequence contain mineralized porphyry clasts derived from erosion of the porphyry deposits. Two zircon grains recovered from one of these mineralized porphyry clasts yielded chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) 206Pb/238U dates of 374.0 ± 1.9 and 371.4 ± 1.6 Ma, which are consistent with previously published ages for mineralized intrusions. This implies that Oyu Tolgoi or other nearby porphyry deposits were exhumed shortly after the main mineralization event. Weakly mineralized granodiorite dikes intruded the postmineralization dacite sequence, as well as Devonian sedimentary and voleaniclastic rocks that structurally overlie the dacite. A weighted mean 206Pb/238U age of 370.6 ± 0.5 Ma for this rock is based on the three youngest grains analyzed by the CA-TIMS technique (MSWD = 1.14). Burial of the Cu-Au deposits at Oyu Tolgoi soon after their exhumation was critical to their preservation. Exhumation and subsequent burial occurred at ~371 Ma, during a short time frame within the overlapping U-Pb zircon ages for the quartz monzodiorite, mineralized porphyry clast, unmineralized dacite sequence, and granodiorite unit. [ABSTRACT FROM AUTHOR]

The Late Triassic Galore Creek porphyry district is the largest accumulation of Cu-Au prospects in British Columbia, Canada, in terms of contained metal. The principal economic resource is the Central zone deposit. It comprises three high-grade centers: the Au-rich North and South gold lenses and the Cu-dominated Central replacement zone. Alteration footprints, ore shells, and porphyry intrusions in these centers dip 45° to 60° to the west in the North gold lens and southwest in the South gold lens and Central replacement zone, indicative of significant postmineral tilting. This inclination created an oblique vertical expression of the Central zone at surface and at depth, providing a +700m depth profile through the deposit. Galore Creek is considered to be the end-member of the silica-undersaturated class of alkalic porphyry Cu-Au deposits. It displays a unique hydrothermal alteration footprint, generally devoid of quartz veining. Despite the lack of crosscutting veins, a paragenetic sequence of several discrete potassic and calcic alteration events has been established. During main-stage alteration, two mineralization events occurred that formed the economic resource in the Central zone. Highly oxidizing fluids derived from porpbyritic syenite to monzonite intrusions produced initial potassic alteration and sulfide mineralization in the North gold lens and South gold lens. Cu-Au ore shells are characterized by a gold-rich core dominated by bornite associated with hematite-dusted orthoclase, specular hematite, and anhydrite. The second period of hydrothermal activity caused brecciation and calcic alteration in the Central replacement zone. The calcic fluids formed hydrothermal cement grading from Ti-rich andraditic to grossularitic garnet in the core of the breccia to a diopside and magnetite-dominated assemblage at the margins. Calcic alteration also formed in the surrounding host rock. This alteration event was followed by potassic alteration and mineralization, characterized by biotite, anhydrite, and chal-copyrite in the Cu-rich ore shell of the Central replacement zone. Most of the Au is hosted in bornite that is spatially associated with oxidized (reddened) rock units dominated by an alteration assemblage of orthoclase ± hematite + specular hematite ± garnet ± anhydrite. High-grade Cu in the Central zone is related to abundant chalcopyrite that has commonly replaced an assemblage of biotite ± magnetite ± diopside. This distinct spatial separation strongly suggests that the local redox environment within the wall rocks governed sulfide and gold distributions. The switch from early Au-rich mineralization to late-stage Cu-dominated mineralization appears to have been controlled by varying redox conditions within the magma. The change from more oxidized alteration assemblages (Fe3+ > Fe2+) to more reduced assemblages (Fe3+ < Fe2+) is indicative of a change in oxidation potential that may have propelled sulfide saturation in the magma and, thus, the subsequent depletion of most of the Au. [ABSTRACT FROM AUTHOR]

Presents a study which evaluated the relationship between igneous activity and mineralization, between high Ag/Au deposits using the timing of mineralization, chemistry, mineral assemblages, fluid inclusions and isotopic patterns in the Tuscarora mining district in Nevada. Description of Eocene magmatism in northeastern Nevada; Geology of the Tuscarora volcanic field; Analysis of the Tuscarora ore deposits.