petrology, geochemistry, sulphide and platinum-group element mineralization of the geordie lake intrusion, coldwell complex, ontario
abstract
pge-bearing geordie lake intrusion is located in the north-central region of the coldwell comples near the town of marathon. the geordie lake intrusion (gli) consists of alternating zones of
layering-free troctolite and olivine gabbro outcropping in the north-central
part of the coldwell alkaline complex, northwestern ontario. the troctolite
exhibits harrisitic texture in which dendritic olivine (f044-56), plagioclase
(an48-57), and skeletal magnetite are the main constituents. small amounts
of clinopyroxene (di36hd60ae4-di30hd66ae4) are present in the troctolite.
the ophitic olivine gabbro consists of clinopyroxene (di4ihd54ae5
di29hd66ae5), plagioclase (an46-54), altered olivine, and skeletal
magnetite. some gabbros contain high-alumina clinopyroxenes
(ti-px4cats48ae48-ti-pxgcats42ae5o). mineral chemistry and
whole-rock geochemistry indicate that the troctolite and gabbro are not
related by differentiation and their parent magma is a relatively evolved
low-alumina tholeiite. the gli is characterized by high sr, rb, ba, th, ta and
light rare-earth element (lree) content but low in ni and cr content.
europium anomalies are absent. fe-ti oxide geothermometry and
geobarometry of the troctolite and olivine gabbro give an average
equilibration temperature of 603° ± 35°c and oxygen fugacity of bar.
disseminated chalcopyrite is the dominant style of cu-sulphide
mineralization in the gli. massive chalcopyrite aggregates are rare.
collections
- retrospective theses [1604]