Field Constraints on Diverse Igneous Processe:~ in the Iron Mask Batholith

The Iron Mask batholith is an Early Jurassic composite alkaline intrusion located southwest of Kamloops in southcentral British Columbia (Figure 2-6-l). It lies in the southern portion of the Quesnel trough in the lntermontane tcctonic belt. It is a northwest-trending body approximately 22 kilomctres long and 5 kilometres wide intruding volcanic and sedimentary rocks of the eastern belt of the Upper Triassic Nicala Group (Prcto, 1979). Emplacement is intcrpreted to have been controlled by ma,jor northwesterly and northeasterly trending fault systems and previous workers have suggested that the batholith is subvolcanic and coeval with the Nicola Group (Northcore, 1977b). tionships between the intrusions comprising I he Iron Mask batholith. Additionally, ficld observadons and maIq>ing have been directed at detailing the nature and origins 111 the enigmatic hybrid and picrite wits. During tht 1992 seaion, fieldwork by the senior author comprised r xonneisazncc mappin& of the batholith ancl !;urrounding \Jicola Group rocks and detailed mapping (I :300 and I: !500) of five selected xcas (Figure 2-6-l). These detail :d geological maps (Figures 2-6-3 to 2-6-7) address sever; I broad qxstions concerning the Nicola Iron Mask relati, rnship arlc tb: magmatic history of the betholil:h, which in< ludes the formation of the hybrid and the: petrologic relationsllip; between the intrusive phases.