z-logo
open-access-imgOpen Access
The role of metamorphic fluids in the formation of ore deposits
Author(s) -
B. W. D. Yardley,
James S. Cleverley
Publication year - 2013
Publication title -
special publication - geological society of london/geological society, london, special publications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.673
H-Index - 132
eISSN - 2041-4927
pISSN - 0305-8719
DOI - 10.1144/sp393.5
Subject(s) - metamorphic rock , geochemistry , geology
Many ore deposits are hosted by metamorphic rocks, and metamorphic fluids have been invoked as a source for various deposits, especially gold deposits. Metamorphic fluid compositions reflect original sedimentary environment: continental shelf sequences yield saline metamorphic fluids with little dissolved gas while metasediments from accretionary and oceanic settings host less saline fluids with significant CO 2 contents. The principal difficulty in reconciling ore deposits with a metamorphic origin is that many form quickly ( c. 1 Ma), whereas metamorphic heating is slow ( c. 10–20 °/Ma). Gravitational instability means that fluid cannot be retained. Metamorphic ores may nevertheless form by: (a) segregation leading to enrichment of pre-existing concentrations; (b) infiltration of water-rich fluids from schists into marbles at high temperature overstepping decarbonation reactions and allowing fast reaction that locally draws down temperature; and (c) rapid uplift driving dehydration reactions owing to pressure drop. Some orogenic lode gold deposits fit well with a purely metamorphic origin during rapid uplift, but others are problematic. At Sunrise Dam, Western Australia, anomalies in Sr-isotope ratios and in apatite compositions indicate a partial mantle/magmatic source. Low salinity, H 2 O–CO 2 fluids commonly associated with hydrothermal gold reflect the effect of salt on gas solubility, not the origin of the fluid.

The content you want is available to Zendy users.

Already have an account? Click here to sign in.
Having issues? You can contact us here