Lithostratigraphy and structure of the early Archaean Doolena Gap greenstone belt, East Pilbara Terrane, Western Australia

D. Wiemer, Christoph Schrank, D.T. Murphy, A.H. Hickman

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    Abstract

    © 2016 Elsevier B.V.The early Archaean East Pilbara Terrane of the Pilbara Craton represents the archetypical granite dome – greenstone keel terrain and preserves much of the primary geological features of dome-and-keel formation. Here we present the first detailed lithostratigraphic and structural transect from marginal gneisses of the Muccan Granitic Complex through 6 km of steeply dipping strata of the western Doolena Gap greenstone belt. Based on overprinting relationships, we identified five deformational events (D1–D5) that can be correlated between four structural domains: (i) marginal orthogneisses of the polyphase Muccan Granitic Complex, (ii) a dominantly mylonitic shear zone (South Muccan Shear Zone) representing a granite dome – greenstone keel detachment zone, (iii) a Central Fold Belt of dominantly mafic greenschists, and (iv) a lower greenschist- to sub-greenschist facies southern Low-Strain Belt. The D1 event in the Low-Strain Belt is recorded in syn-depositional normal faulting (f1) during eruption of deep water low vesicular pillow basalts of the ca. 3.47 Ga Mount Ada Basalt, followed by a conformable transition towards shallow water stromatolites in the Duffer Formation. We interpret the D1 event as the result of upper-crustal extension and subsequent uplift above the Muccan Granitic Complex. The D2 event shows the most intense deformation with syn-anatectic tight folds within the Muccan Granitic Complex and tight to isoclinal transposed folds (F2) and fluid-induced normal faults (f2) within the Central Fold Belt. The D2 event resulted in a regional EW composite S1/2 foliation, and in the development of the mylonitic South Muccan Shear Zone along the dome-keel interface and within the Central Fold Belt, mineral lineations (L2) in conjunction with increasing southward D2 L-tectonite. This D2 event is not observed in a ∼1 km-thick sandstone package (ascribed to the
    Original languageEnglish
    Pages (from-to)121-138
    JournalPrecambrian Research
    Volume282
    DOIs
    Publication statusPublished - 2016

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