U‐Pb zircon age for the Etheridge Group, Georgetown region, north Queensland: Implications for relationship with the Broken Hill and Mt Isa sequences*

U – Pb zircon ages from leucogneiss in the Etheridge Group and their significance for the early history of the Georgetown region, north Queensland

“…Even if they were simply sediments derived from a somewhat older volcanic or plutonic provenance, the zircons will provide an upper limit on their age. In combination with the ages of 1684.2 + 2.1 Ma and 1695.8 + 2.1 Ma obtained by Black et al (1998) for intruding granites, these ages provide a tight stratigraphic fix on the depositional age of the lower parts of the Etheridge Group.…”

“…In their SHRIMP U -Pb zircon study, Black et al (1998) On the basis of their data, Black et al (1998) concluded that deposition of the Etheridge Group began at ca 1700 Ma and may have continued for an estimated 100 million years. The results presented below are complementary to those of that study.…”

“…Various indirect age constraints for the time of deposition have been derived from the metasediments and the felsic igneous rocks that overlie or intrude them, but these have not produced tight temporal constraints. More recently, Black et al (1998) have deduced from U -Pb dating of intruding mafic and felsic rocks that deposition of the oldest known sequence began at, at least, 1700 Ma.…”

Evidence for Early Mesoproterozoic Arc Magmatism in the Musgrave Block, Central Australia: Implications for Proterozoic Crustal Growth and Tectonic Reconstructions of Australia

“…Metamorphism in the central Musgrave Block at ∼1.55 Ga has been proposed by Camacho (1997). Deformation and associated metamorphism of this age is found throughout the Gawler Craton and the NAC (e.g., Connors and Page 1995;Fanning 1995;Black et al 1998;Daly et al 1998). Metamorphism has recently been identified at ca.…”

“…Metamorphism has recently been identified at ca. 1.55 Ga in the Georgetown Inlier (e.g., Fanning 1995;Black et al 1998) and at ca. 1.54 Ga in the Mount Isa Inlier (Connors and Page 1995).…”