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| | | Mangaroon Orogeny D2m/M2m (MAD2) | SP Johnson, S Sheppard, FJ Korhonen, and SA Occhipinti | | | | | Event type | tectonic: intracratonic orogeny | Parent event | | Child events | | Tectonic units affected | | Tectonic setting | orogen: reactivated orogen | Metamorphic facies | | greenschist: chlorite | greenschist: biotite |
| Metamorphic/tectonic features | folded; foliated; sheared; retrogressed; schistose |
| | | Summary | In the Mangaroon Zone D2m was responsible for a pervasive east-southeasterly striking upright schistosity or crenulation schistosity. Metre- to kilometre-scale folds associated with the schistosity are upright, range from close to tight, and plunge moderately or steeply to the west-northwest or east-southeast. Older granites of the Durlacher Supersuite (i.e. those emplaced at or before c. 1675 Ma) have an S2m schistosity of variable intensity. Schistosity is commonly developed parallel to an igneous layering. Metamorphism (M2m) accompanying D2m, was responsible for widespread retrogression of medium- to high-grade M1m assemblages to a common assemblage of sericite, chlorite, quartz plagioclase, with or without biotite. | | | Distribution | Deformation and metamorphism attributed to D2m/M2m is known only from the Mangaroon Zone. The extent of this event elsewhere in the Gascoyne Province is unclear, largely owing to the effects of younger orogenic events, mainly the Mutherbukin Tectonic Event and the Edmundian Orogeny. SHRIMP U–Pb dating of metamorphic monazite and xenotime in thin sections from the Mutherbukin Zone has failed to yield any ages corresponding with the Mangaroon Orogeny despite the presence of voluminous granites of the Durlacher Supersuite. | | | Description | The dominant fabric in rocks of the Pooranoo Metamorphics in the Mangaroon Zone is a pervasive, east-southeasterly striking foliation. The foliation cuts the gneissic layering (S1m) and is parallel to the axial surfaces of metre- to kilometre-scale folds. A widespread lineation defined by the crenulation of S1m by S2m plunges parallel to F2m folds. The F2m folds are upright, range from close to tight, and plunge moderately to steeply to the west-northwest or east-southeast. There are locally large variations in plunge direction over short distances. Nevertheless, there is no crosscutting fabric to suggest a later phase of folding or shearing, and there are no large swings in the strike of the F2m axial surfaces.
In the hinges of F2m folds, M1m mineral assemblages are commonly preserved, but on the limbs these assemblages
are overprinted partly or entirely by M2m metamorphism. This has resulted in the replacement of sillimanite by sericite, and recrystallization of cordierite to sericite and chlorite. Microcline is replaced by sericite, and biotite is commonly recrystallized to a greenish variety and exhibits exsolution of fine ?rutile needles. Plagioclase is partly sericitized. The result is typically a sericite–chlorite–quartz–plagioclase–biotite schist. This assemblage, along with the absence of andalusite, chloritoid, or staurolite, is consistent with the greenschist facies metamorphism of a low Al bulk composition (Spear, 1993).
Metamorphosed mafic rocks are rare in the Pooranoo Metamorphics, and where present they do not seem to contain high-grade M1m assemblages. Assemblages of actinolite, plagioclase, epidote, and titanite suggest upper greenschist-facies metamorphism during M2m. Some actinolite crystals have cores of clinopyroxene. Metamorphosed ultramafic rock contains cummingtonite and serpentine with minor green spinel. Lenticular patches of coarser grained cummingtonite contain cores of orthopyroxene with a relict subophitic texture.
The S2m fabric is present in some of the granites of the Durlacher Supersuite, particularly in the schlieric inclusion-rich granodiorite (P_-DU-ggvs). In addition, some of the granite units, most commonly the Pimbyana Granite and the Dingo Creek Granite, contain a magmatic foliation defined by tabular K-feldspar phenocrysts parallel to S2m. Both granites are composed of a series of sheets parallel to S2m, suggesting that they were emplaced during D2m. However, other granite plutons cut across S2m, and contact metamorphism associated with the granites has recrystallized M2m mineral assemblages. These observations suggest that D2m/M2m in the Mangaroon Zone is of the same age, i.e. c. 1675 Ma, as the granites of the Durlacher Supersuite. The effects of M2m are most pronounced in the schlieric granodiorite (P_-DU-ggvs), for which field relationships suggest that it is the oldest of the granites in the supersuite. Mineralogical changes during M2m consist of epidote and titanite replacement of magnetite and ilmenite in conjunction with plagioclase recrystallization, and recrystallization of biotite to a green variety with exsolved rutile needles. Plagioclase is recrystallized to albite–oligoclase, sericite, and epidote.
Along the western edge of MANGAROOON adjacent to the Minga Bar Fault, medium-grained, porphyritic biotite monzogranite (P_-MO-gmp) is moderately to strongly foliated. The foliation strikes southeast and dips steeply to the southwest, and becomes more intense toward the northeast. About 1.7 km west (SXSMAN6181, Zone 50, MGA 347930E 7373710N ) and 3.6 km south (SXSMAN6158, Zone 50, MGA 350070E 7370420N) of Minga Bar Well a phyllonite derived from porphyritic biotite monzogranite is juxtaposed against medium- to coarse-grained and pebbly sandstone of the Edmund Group. The Edmund Group rocks are folded about open to close upright folds, but are otherwise weakly strained. At the latter locality a folded unconformity is preserved between the Edmund Group rocks and the phyllonite. The majority of the deformation in the shear zone must have pre-dated the deposition of the Edmund Group, and may relate to the Mangaroon Orogeny. The general absence of a stretching lineation suggests that the rocks underwent non-rotational strain. Locally, a steeply dipping stretching lineation defined by biotite or chlorite is developed, and is associated with asymmetric K-feldspar porphyroclast tails, implying southwest side-up on steep normal or reverse faults.
Narrow shear zones (<2 m wide) in granites on the southwestern side of the Minga Bar Fault locally contain S–C fabrics, suggesting dextral strike-slip movement. Deformed porphyritic biotite monzogranite consists of microcline and quartz porphyroclasts wrapped by fine-grained quartz, muscovite, chlorite, untwinned ?albite, titanite, and minor green–brown biotite. This assemblage is consistent with recrystallization under lower greenschist facies conditions. However, the age of this deformation and recrystallization is unknown. It may relate to D2m/M2m or, alternatively, it may relate to the Mesoproterozoic Mutherbukin Tectonice Event or the Neoproterozoic Edmundian Orogeny.
In the areas between the Yannarie River on northwestern MANGAROON and outcrop of the Edmund Group to the northeast, and along the western side of the fault that runs near Old Deep Well and Middle Well, granites of the Durlacher Supersuite are cut by narrow zones of shearing. This tectonic fabric strikes southeast and mostly dips steeply to the southwest. It is commonly parallel to an igneous foliation in the granites, defined by the alignment of tabular K-feldspar phenocrysts. At one locality (SXSMAN5864; Zone 50, MGA 382980E 7373950N), weakly to moderately foliated, porphyritic biotite granodiorite (P_-DU-ggb) is intruded by northeast-striking dykes of muscovite–biotite granite and pegmatite (P_-DU-gmv). The latter contain a foliation, but are not offset, suggesting that they have undergone non-rotational strain. Therefore, granites of the Durlacher Supersuite both intrude the shear zones and are overprinted by them, indicating that supersuite emplacement, at least in part, accompanied the deformation. Most sense-of-shear criteria indicate reverse movement (i.e. southwest side-up), although normal movement is indicated in places. | | | | | | Geochronology | | | Mangaroon Orogeny D2m/M2m | Maximum age | Minimum age | Age (Ma) | 1677 | 1659 | Age | Paleoproterozoic | Paleoproterozoic | Age data type | Inferred | | References | | |
| The S2m fabric is present in some granites of the Durlacher Supersuite, particularly in the schlieric inclusion-rich granodiorite (P_-DU-ggvs), which has an igneous crystallization age of 1677 ± 5 Ma (GSWA 178027, Nelson, 2005; Sheppard et al., 2005). Therefore, the age of the granodiorite provides a maximum age for D2m/M2m. In addition, some of the granite units, in particular the c. 1675 Ma Pimbyana and Dingo Creek Granites, contain a magmatic foliation defined by tabular K-feldspar phenocrysts parallel to S2m. Both granites comprise a series of sheets parallel to S2m, suggesting that they were emplaced during D2m. Other granite plutons, such as the Yangibana Granite, which has an igneous crystallization age of 1659 ± 10 Ma (GSWA 169055, Nelson, 2002), cut across S2m. Furthermore, contact metamorphism associated with some of the granites (e.g. parts of the Dingo Creek Granite) has recrystallized M2m mineral assemblages. These observations suggest that D2m/M2m is of the same age, i.e. c. 1675 Ma, as the bulk of the granites of the Durlacher Supersuite in the Mangaroon Zone. | | | Tectonic Setting | The Mangaroon Orogeny involved pervasive reworking of crust in the Mangaroon Zone at 1680–1660 Ma, and coeval voluminous granitic magmatism, followed by reactivation of faults and shear zones, and the intrusion of granite plutons over a wide area of the Gascoyne Province until c. 1620 Ma. On either side of the Mangaroon Zone, the Boora Boora Zone and the Limejuice Zone appear to have undergone a similar geological evolution, suggesting that the crust is contiguous under the Mangaroon Zone and that the zone formed roughly in its current position. The lack of any volcanic and plutonic activity immediately preceding the Mangaroon Orogeny, either within or flanking the Mangaroon Zone, also precludes that the orogeny is related to closure of an ocean. Instead, the Mangaroon Orogeny represents an episode of intracontinental reworking. Existing geochronological data suggests that D1m/M1m and D2m/M2m may have taken place over a short time, and that they closely followed deposition of sediment precursors to the Pooranoo Metamorphics. This suggests a rapid tectonic event, albeit followed by a prolonged period of granite intrusion. The abundance of strongly peraluminous two-mica granites in the Durlacher Supersuite, and their silicic nature, suggests that they were derived largely by remelting of older crust that included a significant proportion of metasedimentary rock. This conclusion is consistent with the abundance of inherited zircon grains in the dated granites.
The absence of megascopic compressional structures during D1m may be consistent with regional metamorphism related to voluminous granite intrusion during extensional or transtensional orogenesis. In the northern half of the Mangaroon Zone pelitic rocks commonly have a hornfels texture that suggests the presence of large igneous intrusions just below the current level of exposure. Preliminary gravity modelling suggests that the small exposed gabbro intrusions are not part of much larger subsurface intrusions (GSWA, unpublished data), so that the voluminous granitic rocks probably provided the heat. The Mangaroon Zone shows no substantial change in metamorphic grade along or across strike. However, there is a change in grade across the Mangaroon Syncline, but this probably reflects differential uplift during the Neoproterozoic Edmundian Orogeny.
The Mangaroon Orogeny took place in a time frame similar to the 1710–1650 Ma Biranup Orogeny in the Albany–Fraser Orogen (Johnson 2013), which encompassed the intrusion of voluminous granitic magmas into, and the structural reworking of, the southern Yilgarn Craton margin, possibly in a back-arc setting (Kirkland et al., 2011; Spaggiari et al., 2011). This activity was also contemporaneous with magmatism and deformation in the southern Arunta region (Wyborn et al., 1998; Close et al., 2002; Scrimgeour et al., 2002), the Mount Isa Inlier and McArthur Basin (Page et al., 2000) of the North Australian Craton, the western Gawler Craton (Ferris, 2000), and the Broken Hill and Olary Domains (Raetz et al., 2002) of the South Australian Craton.
The Albany–Fraser Orogen of the West Australian Craton and the Warumpi Province (southern part of the Arunta region) of the North Australian Craton (Close et al., 2002, 2003; Scrimgeour 2003) show the greatest degree of similarity to the Capricorn Orogen. Overall, they have a similar age range of tectonism, metamorphism, and igneous activity, although — not surprisingly given the distance between them — in detail there are notable differences. For example, protoliths to the Pooranoo Metamorphics are older than the sedimentary packages in the Warumpi Province (but overlap in age with those in the Barren Basin of the Albany–Fraser Orogen). Furthermore, volcanic rocks are abundant in the Warumpi Province; and the Liebig Orogeny in the Warumpi Province is characterized by high pressure (up to 900 MPa) and temperature (up to 900°C) and is associated with charnockites. The nature of the metamorphism during the Liebig Orogeny and the charnockitic granites contrast with the lower temperatures (<750°C) in the Mangaroon Orogeny, and the peraluminous, xenocryst-rich granites of S-type or mixed S/I-type affinity in the Durlacher Supersuite.
In their plate-tectonic reconstruction of Proterozoic Australia, Myers et al. (1996) suggested that the West, North, and South Australian Cratons did not amalgamate until 1300–1000 Ma. However, recent work suggests that the three cratons were joined before c. 1500 Ma or possibly even before c. 1600 Ma (Wingate and Evans 2003; Giles et al., 2004). Giles et al. (2004) proposed a model in which north- or northeast-directed subduction and progressive accretion of material to the southern margin of the combined West and North Australian Cratons took place between c. 1800 and c. 1600 Ma. The Warumpi Province in the Arunta Inlier is interpreted to have developed outboard of the craton, and to have been accreted to it during the 1640–1630 Ma Liebig Orogeny (Scrimgeour, 2003). If these interpretations of a contiguous latest Paleoproterozoic West and North Australian Craton are correct, then the Mangaroon Orogeny may be linked to tectonic events along the southern margin of the craton (Johnson 2013).
| | | | References | Close, D, Scrimgeour, I, Edgoose, C, Cross, A, Claoué-Long, J and Meixner, A 2002, Identification of new terrains in the southern Arunta Province, central Australia: Geological Society of Australia Abstracts, v. 67, p. 105. | Close, D, Scrimgeour, I, Edgoose, C, Cross, A, Claoué-Long, J and Meixner, A 2003, Redefining the Warumpi Province: Northern Territory Geological Survey, Record 2003–001, 4p. | Ferris, GM 2000, Insights into tectonic evolution of the Western Gawler Craton: MESA Journal, v. 19, p. 28–31. | Giles, D, Betts, PG and Lister, GS 2004, 1.8 - 1.5-Ga links between the North and South Australian Cratons and the Early-Middle Proterozoic configuration of Australia: Tectonophysics, v. 380, p. 27–41. | Kirkland, CL, Spaggiari, CV, Pawley, MJ, Wingate, MTD, Smithies, RH, Howard, HM, Tyler, IM, Belousova, EA and Poujol, M 2011, On the edge: U-Pb, Lu-Hf, and Sm-Nd data suggests reworking of the Yilgarn Craton margin during formation of the Albany-Fraser Orogen: Precambrian Research, v. 187, no. 3–4, p. 223–247, doi:10.1016/j.precamres.2011.03.002. | Myers, JS, Shaw, RD and Tyler, IM 1996, Tectonic evolution of Proterozoic Australia: Tectonics, v. 15, p. 1431–1446. | Nelson, DR 2002, 169055.1: biotite–muscovite monzogranite, Fraser Well; Geochronology Record 128: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Nelson, DR 2005, 178027.1: biotite–muscovite granodiorite, Mangaroon Homestead; Geochronology Record 536: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Page, RW, Jackson, MJ and Krassay, AA 2000, Constraining sequence stratigraphy in north Australian basins: SHRIMP U-Pb zircon geochronology between Mt Isa and McArthur River: Australian Journal of Earth Sciences, v. 47, p. 431–459. | Raetz, M, Krabbendam, M and Donaghy, AG 2002, Compilation of U-Pb zircon data from the Willyama Supergroup, Broken Hill region, Australia: Evidence for three tectonostratigraphic successions and four magmatic events: Australian Journal of Earth Sciences, v. 49, p. 965–983. | Scrimgeour, I, Kinny, PD, Edgoose, C and Close, D 2002, The Liebig Event -- 1640-1630 Ma deformation, magmatism and high grade metamorphism in the southern Arunta province: Geological Society of Australia Abstracts, v. 67, p. 189. | Scrimgeour, IR 2003, Developing a revised framework for the Arunta region, in Annual Geoscience Exploration Seminar (AGES) 2003: Record of abstracts: Northern Territory Geological Survey; Record 2003–001, p. 1–3. | Spaggiari, CV, Kirkland, CL, Pawley, MJ, Smithies, RH, Wingate, MTD, Doyle, MG, Blenkinsop, TG, Clark, C, Oorschot, CW, Fox, LJ and Savage, J 2011, The geology of the east Albany-Fraser Orogen - a field guide: Geological Survey of Western Australia, Record 2011/23, 97p. | Spear, FS 1993, Metamorphic phase equilibria and pressure-temperature-time paths: Mineralogical Society of America, Monograph, 799p. | Wingate, MTD and Evans, DAD 2003, Palaeomagnetic constraints on the Proterozoic tectonic evolution of Australia, in Proterozoic East Gondwana: Supercontinent Assembly and Breakup edited by Yoshida, M, Windley, BF and Dasgupta, S: The Geological Society of London, Special Publication 206, p. 77–91. | Wyborn, LAI, Hazell, M, Page, R, Idnurm, M and Sun, S-S 1998, A newly discovered major Proterozoic granite-alteration system in the Mount Webb region, central Australia, and implications for Cu-Au mineralisation: Australian Geological Survey Organisation, Research Newsletter 28, 7p. |
| | | | Recommended reference for this publication | Johnson, SP, Sheppard, S, Korhonen, FJ and Occhipinti, SA 2022, Mangaroon Orogeny D2m/M2m (MAD2): Geological Survey of Western Australia, WA Geology Online, Explanatory Notes extract, viewed 05 August 2025. <www.dmp.wa.gov.au/ens> |
| | | This page was last modified on 09 March 2022. | | | | | Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zones 49 to 52. All locations are quoted to at least the nearest 100 m. Capitalized names in text refer to standard 1:100 000 map sheets, unless otherwise indicated. WAROX is GSWA’s field observation and sample database. WAROX site IDs have the format ‘ABCXXXnnnnnnSS’, where ABC = geologist username, XXX = project or map code, nnnnnn = 6 digit site number, and SS = optional alphabetic suffix (maximum 2 characters). All isotopic dates are based on U–Pb analysis of zircon and quoted with 95% uncertainties, unless stated otherwise. U–Pb measurements of GSWA samples were conducted using a sensitive high-resolution ion microprobe (SHRIMP) in the John de Laeter Centre at Curtin University, Perth, Western Australia. Digital data related to WA Geology Online, including geochronology and digital geology, are available online at the Department’s Data and Software Centre and may be viewed in map context at GeoVIEW.WA. | | | Further details of geological publications and maps produced by the Geological Survey of Western Australia are available from: Information Centre Department of Mines, Industry Regulation and Safety 100 Plain Street EAST PERTH, WA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 |
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