Neoproterozoic crustal growth in southern Malawi: New insights from petrology, geochemistry, and U–Pb zircon geochronology, and implications for the Kalahari Craton–Congo Craton amalgamation

Tsunogae, Toshiaki; Uthup, Sam; Nyirongo, Mzee Wandembo; Takahashi, Kuniyuki; Rahman, Md. Sazzadur; Liu, Qian; Takamura, Yusuke; Tsutsumi, Yukiyasu

doi:10.1016/j.precamres.2020.106007

Cited by 10 publications

(3 citation statements)

References 92 publications

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“…1.05 Ga Irumide and c . 580–550 Ma Pan‐African Mozambique Belt events (Fritz et al., 2013; Thomas et al., 2022; Tsunogae et al., 2021). In a regional reconstruction, Fritz et al.…”

Section: Regional Geology Tectonics and Thermal Structurementioning

confidence: 99%

“…Northern Malawi is underlain by Ubendian-Usagaran-aged metamorphic and magmatic rocks that experienced low-to high-P granulite-facies metamorphic conditions (750-850°C at 0.5 GPa to ∼880°C at 1 GPa) at c. 2.0 Ga (Ring et al, 1997). Central and southern Malawi is underlain by rocks that likely experienced deformation and metamorphism related to both c. 1.05 Ga Irumide and c. 580-550 Ma Pan-African Mozambique Belt events (Fritz et al, 2013;Thomas et al, 2022;Tsunogae et al, 2021). In a regional reconstruction, Fritz et al (2013) suggest that the crust west of Lake Malawi is dominated by Irumide rocks that acted as a relatively rigid indentor and only experienced minor to moderate reworking in the Pan-African.…”

Section: Geological Historymentioning

confidence: 99%

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Metamorphic Inheritance, Lower‐Crustal Earthquakes, and Continental Rifting

Fagereng,

Diener,

Tulley

et al. 2024

Geochem Geophys Geosyst

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The Malawi Rift is localized within Precambrian amphibolite‐granulite facies metamorphic belts, bounded by up to 150 km long border faults, and generates earthquakes throughout ∼40 km thick crust. Rift‐related faults are inferred to exploit pre‐existing weaknesses that allow rifting of otherwise dry and strong crust. It is unclear what these weaknesses are, and how localization into weak zones can be reconciled with strength required for lower crustal seismicity. We present results of mineral equilibria modeling, which indicate that Proterozoic metamorphism generated dry crust dominated by a quartz‐feldspar assemblage that is metastable at current conditions. For rift propagation to be possible at current cool thermal gradients and in mechanically strong, dry quartzofeldspathic rocks, mid‐ to lower‐crustal strain must be localized into relatively weak, inherited shear zones that deform primarily by aseismic, viscous creep. These shear zones are embedded within high‐strength crust, and interaction between creeping shear zones and enveloped or surrounding rocks may locally increase stress and trigger frictional, seismic slip at mid‐ to lower‐crustal depths. Over time, this interaction may produce a fracture network that allows infiltration of fluids. We therefore suggest that during rifting of previously deformed and metamorphosed crust, major faults are most likely to grow from below, with their location and orientation prescribed by underlying inherited viscous shear zones. In this case, fluids may infiltrate and locally weaken metastable lower crust, including allowing time‐dependent fluid‐driven seismicity and local partial melting, but length‐scales of this weakening is limited by the scale of the permeability network.

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“…1.05 Ga Irumide and c . 580–550 Ma Pan‐African Mozambique Belt events (Fritz et al., 2013; Thomas et al., 2022; Tsunogae et al., 2021). In a regional reconstruction, Fritz et al.…”

Section: Regional Geology Tectonics and Thermal Structurementioning

confidence: 99%

Section: Geological Historymentioning

confidence: 99%

Metamorphic Inheritance, Lower‐Crustal Earthquakes, and Continental Rifting

Fagereng,

Diener,

Tulley

et al. 2024

Geochem Geophys Geosyst

View full text Add to dashboard Cite

show abstract

“…1), or, according to Grantham et al (2013), the Malawian part of the Namuno Terrane. Their host rocks consist of medium-to high-grade paragneisses, granulites and hornblende-biotite gneiss interlayered with sillimanite-garnet metapelites (Kröner et al, 2001), underlain by banded two pyroxene granulites and tonalite-trondhjemite-granodiorite (TTG) gneisses and charnockites (Kröner et al, 2001;Tsunogae et al, 2021).…”

Section: Malawimentioning

confidence: 99%