Rodinia refined or obscured: palaeomagnetism of the Malani igneous suite (NW India)

Abstract

New palaeomagnetic data from the Neoproterozoic felsic volcanic rocks of the Malani igneous suite (MIS) in NW India, combined with data from an earlier study, yield a palaeomagnetic pole with latitude=74.5°N, longitude=71.2°E (dp/dm=7.4/9.7°). A statistically positive fold test and remanences carried by typical high-temperature oxidation (deuteric) minerals support a primary magnetic signature. U/Pb ages from MIS (771–751 Ma) overlap with those for granitoids and dolerite dykes from the Seychelles microcontinent (mainly 748–755 Ma), and palaeomagnetic data for both entities can be matched with a tight reconstruction fit (Seychelles→India: Euler latitude=25.8°N, longitude=330°E, rotation angle=28°). In this Neoproterozoic time interval, MIS and the Seychelles must have been located at intermediate northerly latitudes along the western margin of Rodinia, with magmatism that probably originated in a continental arc. The most reliable, dated palaeomagnetic data (±756 Ma) from MIS, Seychelles and Australia require a crucial reappraisal of the timing and plate dynamics of Rodinia break-up and Gondwana assemblage. These new data necessitate an entirely different fit of East Gondwana elements than previously proposed, and also call to question the validity of the Southwest US–East Antarctic and Australia–Southwest US models. The palaeomagnetic data mandate that Greater India was located west of Australia rather than forming a conjugate margin with East Antarctica in the Mid-Neoptroterozoic. Break-up of Rodinia along western Laurentia may therefore have taken place along two major Neoproterozoic rifts; one leading to separation of Laurentia and Australia–East Antarctica, and the second between Australia and India.