Infiltration of a high-latitude magmatic arc by meteoric waters: hydrogen and oxygen isotopic compositions of 'unaltered' granitoids in the Antarctic Peninsula

摘要

Mineral deposits contain a record of interactions between the lithosphere and the Earth's hydrosphere-biosphere-atmosphere. Over 25 years ago, mineral deposit geologists recognised large-scale 'flooding' of intrusive systems by meteoric waters. Surface waters are now implicated in most crustal processes (diagenesis, sedimentary basin development, deformation, regional metamorphism, alteration of basement, magmagenesis and uplift). Huge meteoric-hydrothermal systems (15 000 km2) have now been defined around continental batholiths and it is postulated that the amount of fluid (H,O, CO,) pumping in and out of the shallow crust (< 10-15 km) may be more than that contained in the hydrosphere and atmosphere combined.5'8 Such fluid fluxes have major implications for heat transfer and geochemical cycling, mineraldeposit formation, and past atmospheric compositions. Fossil hydrothermal systems may contain a record of palaeoclimate.1'2'6-7 However, most climate models assume an inert, dry, crust ('land') and ignore volatile fluxes into and out of the deep Earth. Given the close coupling of the solid Earth, hydrosphere, biosphere and atmosphere in the Earth System, and the ancient record preserved in hydrothermal rocks, the decline in funding and almost complete lack of geoscience in recent Research Council planning are peverse, especially given their new buzrphrase 'Earth System Science'.