Two contrasting granite−greenstone terranes in the Pilbara Craton, Australia: evidence for vertical and horizontal tectonic regimes prior to 2900 Ma
Introduction
Archaean terranes older than 2900 Ma commonly exhibit regional dome and basin patterns, whereas post-2900 Ma terranes are typically characterized by linear structural patterns. This may be evidence of a change in tectonic processes over time, and other workers have used different lines of evidence to argue for evolving tectonic processes during the Archaean (e.g. Choukroune et al., 1995, Davies, 1998). The Pilbara Craton of Western Australia preserves an essentially complete geological record from 3520 to 2400 Ma, making it one of the best areas in the world to study Paleo- to Neoarchaean crustal evolution.
The Pilbara Craton comprises two major tectonic units: an assemblage of pre-2800 Ma granite–greenstone terranes, and an unconformably overlying succession of volcanic and sedimentary rocks that were deposited in the 2770–2400 Ma Hamersley Basin (Fig. 1; Trendall, 1990). The “greenstones” are metamorphosed sedimentary and volcanic rocks, and their hypabyssal equivalents that Hickman (1983) collectively assigned to the Pilbara Supergroup. The “granites” range in composition from diorite and tonalite–trondhjemite–granodiorite (TTG) to syenite, but are dominantly monzogranite and granodiorite, and form structural complexes of multiple intrusions. About 65% of the granite–greenstone basement is concealed by the relatively flat-lying Hamersley Basin succession such that only in the northern part of the craton is this basement exposed over a very large area (Fig. 1). Regional gravity and magnetic data (Blewett et al., 2000) have been used to interpret the underlying granite–greenstone geology of the entire craton (Fig. 2).
Since 1995, the granite–greenstone basement in the northern part of the Pilbara Craton (previously referred to as the “Pilbara Block,” Hickman, 1983) has been the subject of a detailed mapping program by the Geological Survey of Western Australia (GSWA) in collaboration with the Australian Geological Survey Organization (AGSO, recently renamed Geoscience Australia). The mapping has been supported by precise geochronology and geophysical surveys, and has provided a vast amount of new data. The present paper highlights the contrasting geological styles between the western and eastern granite−greenstone terranes.
Section snippets
Regional geology
The granite–greenstone basement in the northern part of the Pilbara Craton contains three granite−greenstone terranes separated by two late tectonic clastic sedimentary basins (Fig. 1, Fig. 2; Hickman, 2001a, Van Kranendonk et al., 2002. The ca. 3280–2920 Ma West Pilbara Granite–Greenstone Terrane (WP) is separated from the ca. 3515–2830 Ma East Pilbara Granite–Greenstone Terrane (EP) by the ca. 3010–2940 Ma Mallina Basin within the Central Pilbara Tectonic Zone (CPTZ; Fig. 1). Southeast of the
“Pilbara Block”
Hickman (1983) provided the first regional geological description of the north Pilbara granite−greenstones, then referred to as the “Pilbara Block.” He interpreted the geology of the Pilbara Block to have resulted from early, dominantly volcanic deposition (Warrawoona Group) on a basement of earlier granite–greenstones, followed by successive periods of deformation, and related sedimentation, volcanism, and granitoid intrusion. Despite recognition of important local stratigraphic variations at
Geology of the EP and WP
Recognition that there is no geological basis for dividing the EP into separate tectono-stratigraphic domains, and that the model of westward-migrating depositional basins across the north Pilbara Craton is not supported by geological or geochronological data, requires reassessment of the basic assumptions and interpretations that have underpinned recent schemes of sequence stratigraphy (Krapez, 1993, Krapez and Eisenlohr, 1998). Lithostratigraphy is not model-dependant, and is thus used in
Discussion
There exists general consensus that the ca. 3280–2920 Ma WP was formed through Phanerozoic-style plate-tectonic processes (Krapez, 1993, Smith et al., 1998, Krapez and Eisenlohr, 1998, Van Kranendonk et al., 2002), but the extent to which such processes also operated in the older EP is currently far more controversial. In the case of the EP, Van Kranendonk et al., 2002, Van Kranendonk et al., 2004 have argued that proponents of horizontal tectonic processes (e.g. Alpine-style thrusting;
Conclusions
The WP and the EP evolved in very different tectonic environments, leading to major differences in rheology, buoyancy and crustal architecture. The terrane-scale structural geology of the EP cannot be satisfactorily interpreted in terms of Phanerozoic-style plate-tectonics. Long-lived, episodic magmatism in the EP is attributed to successive mantle plumes beneath evolving and thickening continental crust, and deformation is attributed to diapiric rise of relatively buoyant granitoids and
Acknowledgements
Although the interpretations and conclusions reached in this paper are the author’s own, they are based on the results of a major collaborative project between the GSWA and Geoscience Australia since 1995. During the 6 year term of the project the author has had countless stimulating discussions on Pilbara geology with geologists involved in this project, in particular Martin Van Kranendonk, R. Hugh Smithies, Ian R. Williams, Leon Bagas, Terry Farrell, David N. Nelson, Caroline A. Strong,
References (77)
- et al.
An extensive, crustally-derived, 3325–3310 Ma silicic volcanoplutonic suite in the eastern Pilbara Craton: evidence from the Kelley Belt, McPhee Dome, and Corunna Downs Batholith
Precambrian Res.
(1999) Archaean tectonic processes: a case for horizontal shortening in the North Pilbara Granite–Greenstone Terrane, Western Australia
Precambrian Res.
(2002)- et al.
Geochronology and stratigraphic relationships of the Sulphur Springs Group and Strelley Granite: a temporally distinct igneous province in the Archaean Pilbara Craton, Australia
Precambrian Res.
(2002) Polydiapirism of the Archaean Mt. Edgar batholith, Pilbara Block, Western Australia
Precambrian Res.
(1989)- et al.
Partial convective overturn of Archaean crust in the east Pilbara Craton, Western Australia: driving mechanisms and tectonic implications
J. Struct. Geol.
(1998) - et al.
Growth and recycling of early Archaean continental crust: geochemical evidence from the Coonterunah and Warrawoona Groups, Pilbara Craton, Australia
Tectonophysics
(2000) - et al.
Age of the Archaean Talga-Talga subgroup, Pilbara Block, Western Australia, and early evolution of the mantle: new Sm-Nd isotopic evidence
Earth Planetary Sci. Lett.
(1987) - et al.
3.1 Ga tuff from the Scholl Belt in the west Pilbara: further evidence for diachronous volcanism in the Pilbara Craton
Precambrian Res.
(1993) - et al.
Structural evolution of the Warrawoona Greenstone Belt and adjoining granitoid complexes, Pilbara Craton, Australia: implications for Archaean tectonic processes
Precambrian Res.
(2001) Sequence stratigraphy of the Archaean supracrustal belts of the Pilbara Block, Western Australia
Precambrian Res.
(1993)
Tectonic settings of Archaean (3325–2775 Ma) crustal-supracrustal belts in the West Pilbara Block
Precambrian Res.
Tensile and compressive growth structures: relationships between sedimentation, deformation, and granite intrusion in the Archaean Coppin Gap greenstone belt, Eastern Pilbara, Western Australia
Precambrian Res.
Field occurrence, geochemistry and petrogenesis of the Archaean Mid-Oceanic Ridge Basalts (A-MORBs) of the Cleaverville area, Pilbara Craton, Western Australia
Lithos
The Sholl Shear Zone, West Pilbara: evidence for a domain boundary structure from integrated tectonic analyses, SHRIMP U–Pb dating and isotopic and geochemical data of granitoids
Precambrian Res.
The Archaean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite
Earth Planetary Sci. Lett.
New constraints on the evolution of the Mallina Basin, and their bearing on relationships between the contrasting eastern and western granite-greenstone terrains of the Archaean Pilbara Craton, Western Australia
Precambrian Res.
Detrital and inherited zircon age distributions—implications for the evolution of the Archaean Mallina Basin, Pilbara Craton, northwestern Australia
Sediment. Geol.
U–Pb zircon geochronology of Archaean felsic units in the Marble Bar region, Pilbara Craton, Western Australia
Precambrian Res.
Evidence for multiphase deformation in the Archean basal Warrawoona Group in the Marble Bar area, East Pilbara, Western Australia
Precambrian Res.
Timing and tectonic significance of Late Archaean, sinistral strike-slip deformation in the Central Pilbara Structural Corridor, Pilbara Craton, Western Australia
Precambrian Res.
Granite-greenstone terranes in the Pilbara Block, Australia, as coeval volcano-plutonic complexes evidence from U–Pb zircon dating of the Mount Edgar batholith
Earth Planetry Sci. Lett.
Extensional structures during deposition of the 3460 Ma Warrawoona Group in the eastern Pilbara Craton, Western Australia
Precambrian Res.
The age of the Fortescue Group, Hamersley Basin, Western Australia, from ion microprobe zircon U–Pb results
Aust. J. Earth Sci.
Record of emergent continental crust ∼3.5 billion years ago in the Pilbara Craton of Australia
Nature
Model for the development of kyanite during partial convective overturn of Archaean granite-greenstone terranes: the Pilbara Craton, Australia
J. Metamorphic Petrol.
Sunrise Hill unconformity: a newly discovered regional hiatus between Archaean granites and greenstones in the northeastern Pilbara Craton
Aust. J. Earth Sci.
Geology of the Pilbara Block and its environs
Geol. Survey Western Aust. Bull.
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