Terrane correlation between Antarctica, Mozambique and Sri Lanka; comparisons of geochronology, lithology, structure and metamorphism and possible implications for the geology of southern Africa and Antarctica

Abstract

Analysis of new lithological, structural, metamorphic and geochronological data from extensive mapping in Mozambique permits recognition of two distinct crustal blocks separated by the Lurio Belt shear zone.

Postcollisional High-Grade Metamorphism, Orogenic Collapse, and Differential Cooling of the East African Orogen of Northeast Mozambique

“…The thermal histories of the tectonic units in this study are notably different and these differences broadly correlate with the established major geological boundaries. The current body of data (this study; Engvik et al 2007;Grantham et al 2008;Jacobs et al 2008;Viola et al 2008;Bingen et al 2009;Daszinnies et al 2009;Macey et al 2010;Thomas et al 2010;Ueda et al 2012) suggests that the Lú rio Belt represents a major boundary zone between blocks with different thermal histories. The data show differences over several tens of Ma, and with a time offset of 50-75 Ma or more, that persisted during cooling over several hundreds of degrees.…”

“…900Њ-1000ЊC and 11 GPa at ca. 615 Ma to upper amphibolite facies ( ∼700ЊC, !0.7 GPa) at around 590-570 Ma (Krö ner et al 1997;Grantham et al 2008).…”

“…The high-grade basement of northeast Mozambique is made up of a collage of gneiss complexes with Meso-to Neoproterozoic protolith ages, which underwent amphibolite facies metamorphism during the late Ediacaran (Grantham et al 2008;Bingen et al 2009;Boyd et al 2010;Macey et al 2010). We refer to the (mostly orthogneissic) complexes north of the Lú rio Belt as the "northern basement," while the single Nampula Complex to the south is accordingly termed "southern basement" (fig.…”

“…In the Mesoproterozoic Nampula Complex, two potentially overlapping phases of metamorphism occurred between ca. 550 and 490 Ma, under mid-to upper amphibolite facies conditions (Macey et al 2007(Macey et al , 2010Norconsult Consortium 2007;Grantham et al 2008;Bingen et al 2009). …”

“…The spatial extent of the Lú rio Belt is also complex and can be defined in different but approximately spatially coincident ways (see Ueda et al 2012), based on (a) discontinuous exposures of Ocua Complex rocks, (b) the structural domains affected by intense aligned fabrics around the major lithological contacts, or (c) a sharp linear magnetic anomaly in the east. The Lú rio Belt has been interpreted in a number of ways, including as (a) a Mesoproterozoic or Ediacaran suture (Pinna et al 1993;Grantham et al 2008), (b) a transpressional, intraorogenic shear zone (Shackleton 1996), (c) a tectonic mé lange (Viola et al 2008), (d) a basal shear zone to the granulite-facies nappes (exposed to its north) that later became a focal zone of increasing q2 q3 q4 fold strain (Viola et al 2008), (e) an accommodation zone between two thermomechanically different parts of the orogen (Jacobs et al 2008), or more generally (f) as crustal-scale discontinuity of unknown origin that was repeatedly reactivated and reworked with varying kinematics over a wide area (Ueda et al 2012). In the eastern Lú rio Belt, peak metamorphic conditions and pressure-temperature-time evolution indicate an almost isothermal decompression path from ca.…”