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.