Petrology and Geochemistry of the Grubergebirge Anorthosite and Marginal Rocks, Central Dronning Maud Land: Further Characterization of the Late Neoproterozoic Magmatic Event in East Antarctica

作者：Ravikant Vadlamani^*; Dharwadkar A; Golani P R; Ravindra R

来源：Journal of the Geological Society of India, 2011, 78(1): 7-18.

DOI：10.1007/s12594-011-0062-z

• Gruber anorthosite-ferrodiorite
• Neoproterozoic magmatism
• East Antarctica

The Grubergebirge anorthosite, a Late Neoproterozoic massif-type anorthosite, was emplaced into Late Mesoproterozoic-aged metamorphosed orthogneisses and supracrustal rocks in the Wohlthat Mountains. Mineralogically and chemically, the marginal rocks to the anorthosite massif classify as ferromonzodiorite and ferromonzonite.
Variations in trace and rare earth element abundances and normalized patterns between the anorthosite and associated marginal ferromonzodiorite (and minor ferromonzonite) and distinct differences between the ferromonzodiorite and ferromonzonite have been observed. Whereas the magmas from which the anorthosite crystallized have been slightly contaminated by incorporating crustal material (now occurring as enclaves), the marginal ferromonzodiorite represent rocks that originated due to mixing (hybridization) of injected primitive ferrodiorite magma(s) with preexisting crustal material, resulting in the hybrid ferromonzodiorite.
These events at the margin of the massif anorthosite represent a widespread Late Neoproterozoic magmatic event with accompanying crustal mixing; all these rocks were thereafter metamorphosed under amphibolite- to granulitefacies conditions during the Early Cambrian Period. In contrast, unmetamorphosed dykes with a ferrodiorite mineralogy, of Late Cambro-Ordovician age, have been found that probably represent a part of the late magmatic suites of the south Petermannketten (Zwiesel).

• 出版日期2011-7