Geochronology
When U-Pb zircon age determinations, using thermal ionization mass spectrometry (TIMS) by Feely et al. (2003) are combined with Re-Os molybdenite age determinations (Feely et al. 2003; Selby et al. 2004; Feely et al. 2007), a Connemara granites’ emplacement sequence ranging over approximately 40 Ma emerges. Granite magmatism began in the Connemara sector of the orogen with the ascent and emplacement of the satellite Omey granite at approximately 422 Ma (Feely et al. 2007). The age of emplacement of the other satellite plutons is uncertain, however in the case of the Roundstone granite unpublished field evidence indicates that it predates the batholith (Leake pers comm.). Friedrich et al. (1999) suggest that resetting of mica ages to 415 Ma in the country rocks are due to the heat from the granite. We assume therefore that the four satellites were emplaced pre-410 Ma. Re-Os ages for granite related molybdenite mineralization at the western end of the Galway Batholith (Feely et al. 2003; Selby et al. 2004) yield ages of between 407 (Murvey) and 410 Ma (Mace Head). Pidgeon (1969) determined a bulk zircon age of 412 ±15 Ma for the Carna granite which hosts the molybdenite bearing quartz veins at Mace Head. The main body of magma, the Galway Batholith was emplaced between 410 Ma and 380 Ma (Feely et al. 2003). The Oughterard Granite, dated at 462.5 ±1.2 Ma (Friedrich et al. 1999) and outside of the aforementioned approximate 40 Ma time range, is included in the KML emplacement model ("Google Earth" file), so as to complete the story of granite emplacement on Connemara.