Abstract The genesis of mineral deposits has been widely linked to specific tectonic settings, but has less frequently been linked to tectonic processes. Understanding processes of oceanic and continental collision tectonics is crucial to understanding key factors leading to the genesis of magmatic-, metamorphic-, hydrothermal-, and sedimentary-related mineral deposits. Geologic studies of most ore deposits typically focus on the final stages of concentration and emplacement. The ultimate source (mantle, lower crust, upper crust) of mineral deposits in many cases remains more cryptic. Uniquely, along the Tethyan collision zones of Asia, every stage of the convergence process can be studied from the initial oceanic settings where ophiolite complexes were formed, through subduction zone and island-arc settings with ultrahigh- to high-pressure metamorphism, to the continental collision settings of the Himalaya, and advanced, long-lived collisional settings such as Afghanistan, the Karakoram Ranges, and the Tibetan plateau. The India-Asia collision closed the intervening Neotethys ocean at ~50 Ma and resulted in the formation of the Himalayan mountain ranges, and increased crustal thickening, metamorphism, deformation, and uplift of the Karakoram-Hindu Kush ranges, Tibetan plateau, and older collision zones across central Asia. Metallogenesis in oceanic crust (hydrothermal Cu-Au; Fe, Mn nodules) and mantle (Cr, Ni, Pt) can be deduced from ophiolite complexes preserved around the Arabia/India-Asia collision (Oman, Ladakh, South Tibet, Myanmar, Andaman Islands). Tectonic-metallogenic processes in island arcs and ancient subduction complexes (VMS Cu-Zn-Pb) can be deduced from studies in the Dras-Kohistan arc (Pakistan) and the various arc complexes along the Myanmar-Andaman segment of the collision zone. Metallogenesis of Andean-type margins (Cu-Au-Mo porphyry; epithermal Au-Ag) can be seen along the Jurassic-Eocene Transhimalayan ranges of Pakistan, Ladakh, South Tibet, and Myanmar. Large porphyry Cu deposits in Tibet are related to both precollisional calc-alkaline granites and postcollisional alkaline adakite-like intrusions. Metallogenesis of continent-continent collision zones is prominent along the Myanmar-Thailand-Malaysia Sn-W granite belts, but less common along the Himalaya. The Mogok metamorphic belt of Myanmar is known for its gemstones associated with regional high-temperature metamorphism (ruby, spinel, sapphire, etc). In Myanmar it is likely that extensive alkaline magmatism has contributed extra heat during the formation of high-temperature metamorphism. This paper attempts to link metallogeny of the Himalaya-Karakoram-Tibet and Myanmar collision zone to tectonic processes derived from multidisciplinary geologic studies.

Abstract Gold mineralization at the Damang deposit is unique among known deposits in Ghana, comprising two distinct styles of mineralization. These include a stratigraphically controlled auriferous quartz-pebble metaconglomerate that is overprinted by later gold contained in a complex fault-fracture vein array with surrounding hydrothermal alteration. A systematic study using portable, field-based infrared reflectance spectroscopy has proven to be a valuable exploration tool at Damang. Spectral parameters such as the ferrous-iron response, the AlOH/H 2 O absorption depth ratio, and automated mineral identification successfully distinguish metasedimentary and metadoleritic lithologic units at Damang. Systematic variations in these parameters, together with the water/OH absorption depth, both downhole and in three-dimensional models, provide vectors to gold mineralization. The spectral parameters AlOH wavelength and MgOH wavelength are used to define the regolith profile at Damang, throughout which the ferrous-iron response parameter provides a reliable indicator of gold mineralization. All recorded changes in spectral parameters can be linked to sample petrography and are supported by mineral-chemical data. These results show that portable infrared spectroscopy can be used in a variety of roles, including regolith mapping, geologic mapping and logging, and recognition of hydrothermal alteration patterns, as each lithology and alteration style exhibit distinct and identifiable spectral characteristics. These spectrally derived alteration proxies indentify a broader zone of potential gold mineralization than gold grades alone, providing a larger target for exploration. The rapidity of data collection and ease of analysis of spectral data make infrared reflectance spectroscopy a useful methodology that can be readily incorporated into both preexisting and established exploration programs in other tropical terrains.

Phanerozoic granitoids have been classified into magnetite and ilmenite series based on the abundance of magnetite, which is related to the Fe 2 O 3 /FeO ratio of the rock and the oxygen fugacity ( f O 2 ) of its parent magma. We have examined the temporal and spatial distributions of both series in Archean granitoids from the Barberton region and the Johannesburg Dome of the Kaapvaal Craton, South Africa. The oldest syntectonic TTG (tonalite-trondhjemite-granodiorite) granitoids (ca. 3450 Ma in age) were found to be ilmenite series, whereas some intermediate-series granitoids occurred locally. Younger and larger syntectonic TTGs (e.g., the 3230 Ma Kaap Valley plutons) comprise nearly equal quantities of magnetite and ilmenite series. The major 3105 Ma calc-alkaline batholiths (e.g., Nelspruit batholith), emplaced during the late-tectonic stage, comprise mostly magnetite-series granitoids, suggesting that an oxidized continental crust already existed by this time. The rare earth element ratios and δ 18 O values, as well as the Fe 2 O 3 /FeO ratios, of the Archean magnetite-series granitoids suggest that their magmas were generated from the partial melting of subducted oceanic basalts that had been oxidized by interaction with seawater on mid-oceanic ridges; the processes of magma generation were much like those for Phanerozoic magnetite-series granitoids. This further suggests that the concentrations of oxidants (O 2 and/or SO 4 2− ) in the Archean oceans were similar to those in Phanerozoic oceans. Low concentrations of chlorine in the magmas, as well as deep levels of granite erosion, appear to explain the absence of major mineral deposits associated with the Kaapvaal granitoids.