Role of late magmatic fluids in Merensky-type platinum deposits: A discussion

Research Article| June 01, 1988 Role of late magmatic fluids in Merensky-type platinum deposits: A discussion Stephen J. Barnes; Stephen J. Barnes 1Commonwealth Scientific and Industrial Research Organization, Division of Exploration Geoscience Wembley, Western Australia 6014, Australia Search for other works by this author on: GSW Google Scholar Ian H. Campbell Ian H. Campbell 2Research School of Earth Sciences, Australian National University, Canberra, A.C.T. 2601, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Stephen J. Barnes 1Commonwealth Scientific and Industrial Research Organization, Division of Exploration Geoscience Wembley, Western Australia 6014, Australia Ian H. Campbell 2Research School of Earth Sciences, Australian National University, Canberra, A.C.T. 2601, Australia Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1988) 16 (6): 488–491. https://doi.org/10.1130/0091-7613(1988)016<0488:ROLMFI>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Stephen J. Barnes, Ian H. Campbell; Role of late magmatic fluids in Merensky-type platinum deposits: A discussion. Geology 1988;; 16 (6): 488–491. doi: https://doi.org/10.1130/0091-7613(1988)016<0488:ROLMFI>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A number of features of platinum group element (PGE)-rich layers in layered intrusions provide evidence for the involvement of late magmatic fluids. The presence of pegmatitic textures, intergrowth of sulfides with intercumulus volatile-rich phases, high Cl content in volatile-bearing phases, and association with graphite and fluid inclusions have been taken by some authors as evidence for postcumulus transport and deposition of PGE by a fluid phase of late magmatic derivation. We argue that these apparently hydrothermal features are the result of postcumulus processes superimposed on layers whose extensive, uniform PGE concentrations were formed by magmatic cumulus processes.The association with pegmatites and volatiles arises from the relatively low solidus temperatures of orthocumulate layers, which cause these layers to act as traps for fluids migrating through the crystal pile. These fluids are mostly derived by vapor exsolution from fractionated intercumulus melt and are consequently enriched in CI. Redissolution of these fluids into vapor-undersaturated trapped liquid in orthocumulate layers causes recrystallization and formation of gabbro pegmatites.Immiscible sulfide-oxide liquid solidifies at near-solidus temperatures in the interstitial pore space between early-crystallizing silicate minerals, and it is forced into areas occupied by late-crystallizing CI-bearing silicates. This accounts for intergrowths of Cu and PGE-rich sulfides with amphiboles and micas, a ubiquitous feature of sulfide-bearing gabbros.Further exsolution of a vapor phase during late stages of crystallization causes deuteric alteration, formation of fluid inclusions, and possible local redistribution of sulfides and PGE. Cooling of this vapor phase may lead to precipitation of graphite at or below the orthocumulate solidus. Graphite deposition may be catalyzed by sulfides and PGE. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.