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| | | Mangaroon Orogeny D1m/M1m (MAD1) | SP Johnson, S Sheppard, FJ Korhonen, and SA Occhipinti | | | | | Event type | deformation: undivided | Parent event | | Child events | | Tectonic units affected | | Tectonic setting | orogen: reactivated orogen | Metamorphic facies | | amphibolite: sillimanite | amphibolite: sillimanite - K-feldspar |
| Metamorphic/tectonic features | foliated; gneissose; diatexitic; granofelsic; metatexitic |
| | | Summary | In the Mangaroon Zone, D1m was responsible for a regionally extensive gneissic layering or foliation that developed at amphibolite facies or upper amphibolite facies metamorphic grade. There are few other structures, apart from some small recumbent folds, that can be attributed to D1m. In the northern half of the Mangaroon Zone diatexites and metatexites are rare. Many of the rocks in this region have grano- or hornfelsic textures, suggesting that M1m may be related to the intrusion of voluminous granites. In the southern half of the Mangaroon Zone, diatexites and metatexites are widespread and voluminous. | | | Distribution | All of the information on the discrete deformational and metamorphic events related to the Mangaroon Orogeny comes from the Mangaroon Zone in the Gascoyne Province. Outside this zone it is difficult to be confident that any of the mineral assemblages were formed during the Mangaroon Orogeny, due to the pervasive effects of younger orogenic events, in particular the Mutherbukin Tectonic Event and the Edmundian Orogeny. In other tectonic units, which were believed to have been affected by the Mangaroon Orogeny, the age constraints are insufficient to assign any particular fabric to D1m or D2m. | | | Description | The oldest fabric in the Mangaroon Zone is a regionally extensive gneissic layering or foliation (S1m) developed in the metamorphic rocks of the Pooranoo Metamorphics and Gooche Gneiss. In the area around the Star of Mangaroon mine this fabric includes stromatic leucosomes in metatexite and diatexite migmatite. The S1m gneissic layering is cut by an upright foliation associated with F2m folds. Folds associated with D1m are difficult to identify, but about 5 km northwest of James Bore (Zone 50, MGA 368020E 7380090N) a steeply inclined, metre-scale isoclinal F1m fold in pelitic gneiss in the hinge of a large F2m fold is exposed. Other evidence for F1m folds comes from small-scale F1m/F2m fold interference structures in psammite near the Star of Mangaroon mine (Zone 50, MGA 372200E 7360090N). However, there are also larger scale fold interference structures in the Gooche Gneiss about 4 km northeast of Six Mile Well and 6 km east of Burridges Well. In addition, F1m inclined folds are inferred from downward-facing metamorphosed feldspathic sandstone beds in the hinge of an F2m fold west of Doorawarrah Well (Zone 50, MGA 355550E 7376850N). The dominant foliation or gneissic layering in granodioritic to monzogranitic rocks of the Gooche Gneiss is also interpreted to have formed during D1m. Augen of microcline and quartz are wrapped by fine-grained quartz, plagioclase, biotite, and muscovite. The micas have a strong preferred orientation and define the foliation.
Mineral assemblages developed during M1m are commonly well preserved in the fold hinges of macroscopic F2m folds. Pelitic gneiss and granofels contain assemblages including biotite–muscovite–quartz–plagioclase–sillimanite, quartz–biotite–cordierite–plagioclase–muscovite(– sillimanite), and plagioclase–biotite–quartz–sillimanite–muscovite–cordierite. All assemblages include accessory tourmaline and iron oxide minerals. Sillimanite consists of seams and patches of fibrolite that typically nucleate on biotite crystals or large muscovite plates. In some rocks sillimanite also forms small prismatic crystals intergrown with plagioclase and quartz.
On MANGAROON, garnet formation during D1m is restricted to two small areas: the area around Mount Thompson near the southern edge of the sheet area, and about 4 km northwest of Bookatharra Well in the northwestern part of the map sheet. Southeast of Mount Thompson (Zone 50, MGA 379090E 7345630N) pelitic gneiss — in association with diatexite migmatite — consists of sillimanite–biotite–quartz–muscovite–garnet(–cordierite). Northwest of Bookatharra Well non-migmatitic pelitic gneiss comprises cordierite–biotite–muscovite–sillimanite with minor layers of garnet–quartz–cordierite–biotite–sillimanite.
The non-migmatitic pelitic gneiss and granofels in the area north and northwest of James Bore commonly have layers rich in porphyroblasts up to 1 cm in diameter. The porphyroblasts overprint S1m and give rise to prominent pits on weathered surfaces. The porphyroblasts consist of fine-grained polygonal plagioclase, biotite, prismatic sillimanite, and minor muscovite.
The assemblages outlined above are typical of high and low Al pelites regionally metamorphosed at low pressures (Spear, 1993). The absence of garnet — other than locally where it may have been stabilized by high whole-rock MnO contents — and staurolite or kyanite, combined with the abundance of cordierite, suggests that the rocks were not metamorphosed at intermediate to high pressures. The cordierite- and sillimanite-bearing assemblages noted above are stable at about 600–630°C at 2 kbar or 650–700°C at 5 kbar (Spear, 1993). The appearance of sillimanite in non-migmatitic pelitic gneiss is consistent with a metamorphic grade equivalent to amphibolite facies.
The migmatites around the Star of Mangaroon mine are associated with pelitic gneisses consisting of cordierite–biotite–quartz–microcline–sillimanite(–muscovite), or quartz–cordierite–biotite–microcline–sillimanite(–plagioclase). The major difference with non-migmatitic pelitic gneisses north of the Mangaroon Syncline is the paucity or absence of plagioclase or muscovite, and the appearance of microcline in gneisses associated with the migmatites. The co-existence of sillimanite and K-feldspar is consistent with the onset of the equivalent of upper amphibolite facies conditions (Bucher and Frey). These changes suggest that melt formed due to either of the following reactions:
muscovite + plagioclase + quartz = sillimanite + K-feldspar + melt (1)
muscovite + plagioclase + quartz = sillimanite + K-feldspar + biotite + melt (2).
The temperatures at which these reactions take place are strongly dependent on pressure, but a minimum temperature of approximately 650°C is required (Spear, 1993). These reactions do not produce more than about 5% partial melting (Clemens and Vielzeuf, 1987) and are unlikely to be the reaction responsible for the diatexite migmatites, which correspond to large degrees of melt. The diatexite melts are a medium-grained, muscovite- and biotite-bearing granodiorite to tonalite that also contain cordierite, with or without minor garnet and sillimanite. Paleosomes consist of biotite, cordierite, sillimanite, muscovite, and plagioclase, or cordierite, plagioclase, quartz, sillimanite, and muscovite. The diatexites may have been derived from farther below at higher temperatures by biotite dehydration, which, on both theoretical and experimental grounds, can produce large amounts of melting (Clemens and Vielzeuf, 1987).
Psammitic schist and feldspathic metasandstone is a widespread rock type, but is a poor indicator of metamorphic grade. Some layers of psammitic schist west and northwest of James Bore contain rosettes of fine-grained magnetite and biotite, commonly with leucocratic haloes. The rosettes overprint the S1m fabric, but are commonly flattened within the compositional layering and are cut by the S2m foliation. Rosettes range from nearly spherical and 2 cm in diameter to oblate and more than 10 cm long. Leucocratic haloes are mostly a few millimetres wide but may exceed 10 mm. The origin of these rosettes is unclear. Garnet is also locally present in psammitic schist on EDMUND.
The dominant foliation or gneissic layering in granodioritic to monzogranitic rocks of the Gooche Gneiss is also interpreted to have formed during D1m. Augen of microcline and quartz are wrapped by fine-grained quartz, plagioclase, biotite, and muscovite. The micas have a strong preferred orientation and define the foliation. | | | | | | Geochronology | | | Mangaroon Orogeny D1m/M1m | Maximum age | Minimum age | Age (Ma) | 1689 | 1677 | Age | Paleoproterozoic | Paleoproterozoic | Age data type | Inferred | | References | | Wingate et al. (2017a) | Wingate et al. (2017a) |
| | Nelson (2005) | Sheppard et al. (2005) |
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| The age of D1m/M1m in the Mangaroon Zone is tightly constrained. The oldest granitic units in the Durlacher Supersuite are schlieric monzogranites to granodiorites (P_-DU-gmbi, P_-DU-ggvs). The oldest dated sample (GSWA 208365) is a medium-grained, moderately deformed, biotite granodiorite that forms a more even-textured part of abundant, but poorly outcropping schlieric granodiorites. This sample yielded a magmatic crystallization age of 1689 ± 6 Ma (Wingate et al., 2017a). Other schlieric granitic rocks have been dated throughout the Mangaroon Zone giving ages of 1683 ± 7 Ma (GSWA 208372; Wingate et al., 2017b), 1682 ± 4 Ma (GSWA 208318; Wingate et al., 2013) and 1677 ± 5 Ma (GSWA 178027; Nelson, 2005). Abundant metasedimentary enclaves with high-grade D1m gneissic fabrics and M1m metamorphic assemblages are enclosed within the schlieric granites, suggesting that granite magmatism post-dates the peak of M1m. However, in sample GSWA 208318 (Wingate et al., 2013) the gneissic enclaves yielded zircons with an age of 1808 ± 4 Ma, indicating that they are part of the Moorarie Supersuite (P_-MO-mggn) and not the Pooranoo Metamorphics (P_-PO-md) and so the age of the gneissic fabrics is questionable. The best estimate for the timing to D1m metamorphism is provided by the age of metamorphic zircons obtained from a pelitic gneiss and granofels of the Pooranoo Metamorphics (P_-PO-mln) at 1680 ± 13 Ma (GSWA 169094, Nelson 2004). This age is also within uncertaintly of the schlieric granitic rocks that enclose and truncate S1m fabrics within the metasedimentary enclaves. These relationships suggest that the age of D1m/M1m ranges between c. 1683 and 1677 Ma.
| | | 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 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 suggest 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, the Mangaroon Orogeny may be linked to tectonic events along the southern margin of the craton (Johnson 2013). | | | | References | Bucher, K and Frey, M 2002, Petrogenesis of metamorphic rocks: Springer Verlag, Berlin, 341p. | Clemens, JD and Vielzeuf, D 1987, Constraints on melting and magma production in the crust: Earth and Planetary Science Letters, v. 86, p. 287–306. | 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 2004, 169094.1: quartz–plagioclase–biotite–sillimanite gneiss, Woorkadjia Pool; Geochronology Record 88: 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. | Sheppard, S, Occhipinti, SA and Nelson, DR 2005, Intracontinental reworking in the Capricorn Orogen, Western Australia: The 1680–1620 Ma Mangaroon orogeny: Australian Journal of Earth Sciences, v. 52, p. 443–460, doi:10.1080/08120090500134589. | 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. | Wingate, MTD, Kirkland, CL and Korhonen, FJ 2013, 208318.1: metagranite, Brown Well; Geochronology Record 1174: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wingate, MTD, Lu, Y, Johnson, SP and Korhonen, FJ 2017a, 208365.1: biotite metagranodiorite, Kimbers Well; Geochronology Record 1356: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Wingate, MTD, Lu, Y, Korhonen, FJ and Johnson, SP 2017b, 208372.1: monzogranite, Seven Mile Well; Geochronology Record 1360: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | 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 D1m/M1m (MAD1): 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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