0000000000049521
AUTHOR
Steven D. Boger
LA-ICP-MS U–Pb dating of detrital rutile and zircon from the Reynolds Range: A window into the Palaeoproterozoic tectonosedimentary evolution of the North Australian Craton
Abstract The Palaeoproterozoic Reynolds Range of the Arunta Region, central Australia, comprises a series of shallow marine clastic sediments (Reynolds Range Group) which overlies deeper water sequences of turbidites (Lander Rock Formation) and minor sandstones (“unnamed sandstone”). U–Pb age data collected from detrital rutile and zircon in these rocks indicates these sequences contain very similar age spectra, although with a notable and important shift to younger ages within the stratigraphically younger Reynolds Range Group. Detrital zircons from the “unnamed sandstone” directly underlying the unconformity with the Reynolds Range Group contain a major age component at ca. 1860 Ma, toget…
Indo-Antarctic derived detritus on the northern margin of Gondwana: evidence for continental-scale sediment transport
Provenance studies from Cambro-Ordovician sediments of the North Gondwana passive margin typically ascribe a North African source, a conclusion that cannot be reconciled with all observations. We present new U-Pb ages from detrital rutile and zircon from Late Ordovician sediments from Saxo-Thuringia, Germany. Detrital zircons yield age populations of 500–800 Ma, 900–1050 Ma and 1800–2600 Ma. The detrital rutile age spectra are unimodal with ages between 500 and 650 Ma and likely represent, together with the 500–800 Ma and 1800–2600 Ma zircon populations, detritus sourced predominantly from North Africa. In contrast, the c. 950 Ma zircons, which are persistently found in Cambro-Ordovician se…
The importance of iron speciation (Fe+2 /Fe+3 ) in determining mineral assemblages: an example from the high-grade aluminous metapelites of southeastern Madagascar
Metapelitic granulites from the Anosyen domain of southeastern Madagascar are exposed in three intercalated formations: the Amparihy, Bakika and Ihosy formations. Although mineralogically distinct from each other, the rocks from these formations show very similar bulk-rock compositions when measured on a FeT basis. The preserved mineral assemblages thus do not reflect differences in the ratios of the main rock-forming oxides (i.e. Al2O3:FeT:MgO), but instead reflect variations in the pre-metamorphic oxidation state of the protolith rocks. These differences in oxidation state are manifested via differences in iron speciation – either Fe+2 or Fe+3. The relatively reduced rocks of the Amparihy…