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(a) Two-pyroxene granulite (sample FR12A2) with assemblage clinopyroxene (cpx)–orthopyroxene (opx)–plagioclase (pl) and relict igneous texture. (b) Clinopyroxene–plagioclase granulite (sample FR13A1) with spinel (spl). (c) Clinopyroxene– plagioclase granulite with biotite (bt) replacing clinopyroxene and spinel (sample FR13A1). (d) Finer-grained portion of clinopyroxene–plagioclase granulite (FR13A2) showing relict igneous texture. (e, f) felsic garnet (grt) granulite with antiperthitic plagioclase. (field of view in a, b, c, e, f is * 3 mm; in d is * 6 mm).
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The first zircon U–Pb SHRIMP dating on high-grade meta-igneous units in the northernmost parts of the Fraser Belt along the southern margin of the Western Australian Yilgarn Craton, reveal crystallisation ages between 1299 + 10 and 1250 + 23 Ma. A small number of older xenocrystic zircons, incorporated in some samples, indicate the presence of Late...
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Context 1
... FR12A2 was collected from a mafic two-pyroxene granulite with a granoblastic texture, which in places shows a relict igneous texture. The clinopyroxenes clearly show exsolution lamellae, while the feldspar in places shows antiperthitic intergrowths, both indicative of rela- tively high-temperature metamorphism (Figure 4a-d). The absence of garnet suggests low pressures during metamorphism. ...
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Citations
... The Kepa Kurl Booya Province is further subdivided into the Biranup, Nornalup, and Fraser lithotectonic zones (see Fig. 1; Spaggiari et al., 2009;Spaggiari et al., 2011). Two major stages of the AFO have been identified: Stage I (1345-1260 Ma) is considered to mark initial arc accretion, crustal thickening and emplacement of 1330-1280 Ma Recherche Supersuite granitic magmatism (Bodorkos and Clark, 2004;Clark et al., 2000;De Waele and Pisarevsky, 2008;Smithies et al., 2013;Spaggiari et al., 2014a). This event was followed by a period of uplift and erosion, which deposited sediments unconformably onto exposed basement in adjacent basins. ...
... Geochronological work on the Fraser Zone suggests coeval mafic magmatism and peak metamorphic conditions during Stage I (Glasson et al., 2019;Clark et al., 2014). Zircon U-Pb crystallisation ages for the Fraser Gabbros range from 1315 Ma to 1290 Ma (De Waele and Pisarevsky, 2008;Glasson et al., 2019). Metamorphism is recorded as early as 1304 ± 7 Ma in zircon growth rims (Spaggiari et al., 2015;Wingate and Bodorkos 2007), and peak metamorphic conditions are modelled at 850-950 • C, with pressures of 7-9 kbar at ~1290 Ma, which were followed by a period of isobaric cooling at around 9 kbar (Clark et al., 2014;Glasson et al., 2019;Oorschot, 2011). ...
The trace element signature and U-Pb systematics of apatite are useful in identifying petrogenic processes and tracking crust through the ∼375–600 °C thermal interval. Furthermore, as apatite is more abundant in mafic rocks than other more conventional U-Pb chronometers (e.g. zircon), it may be better suited to constrain magmatic ore systems. This work focuses on a case study of apatite from the Nova-Bollinger Ni-Cu magmatic sulfide deposit in the Fraser Zone of the Albany Fraser Orogen, Western Australia. LA-ICP-MS analysis is used to characterise the U-Pb systematics and trace element chemistry of apatite across four rock types at Nova-Bollinger. These analyses are combined with whole-rock geochemistry and petrography to resolve the poorly understood thermal evolution of Nova-Bollinger after peak metamorphic conditions.
Apatite U-Pb data indicate an initial 15 °C/my cooling rate to 1284 ± 12 Ma from peak metamorphic conditions of ∼850 °C at 1304 ± 22 Ma. After 1284 Ma the cooling rate dramatically slowed to 1.2 °C/my until at least 1225 ± 17 Ma. Most apatite retains an igneous trace element signature where thermal diffusion has not influenced trace element concentrations, suggesting that any exposure to temperatures above ∼670 °C was short-lived or trace element diffusion was slow. Furthermore, trace element chemistry discriminates apatite that crystallised from an evolved intercumulus disequilibrium liquid, and apatite that crystallised in equilibrium with the mineral assemblage of more fractionated rocks. The new results from this study highlight the change from a fast to slow cooling regime in this litho-tectonic zone, likely driven by ebbing regional magma emplacement. This new information enables better understanding of the tectono-magmatic evolution of the Proterozoic Nova-Bollinger deposit and the broader Fraser Zone.
... Dating magmatic crystallisation of Fraser Complex mafic rocks is complicated by overprinting 1300-1290 Ma high-grade metamorphism (e.g. C. Clark et al., 2014;D. J. Clark et al., 1999;De Waele & Pisarevsky, 2008); however, Glasson et al. (2019) obtained a U-Pb date of 1315 ± 5 Ma from a texturally distinctive zircon-ilmenite association ascribed to igneous crystallisation. ...
The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but exploration has been hampered by poor constraints on its post-depositional history that has compromised understanding of the tectonostratigraphic evolution of the basin. The Derim Derim Dolerite occupies an important position in the event chronology of the McArthur Basin, having intruded the Roper Group prior to post-Roper basin inversion, and it is also a major component of Mesoproterozoic intraplate mafic magmatism in northern Australia. Since 1997, the Derim Derim Dolerite has been assigned a magmatic crystallisation age of 1324 ± 4 Ma (all uncertainties are 95% confidence), based on unpublished sensitive high-resolution ion micro probe (SHRIMP) U–Pb analyses on baddeleyite attributed to a dolerite sample from Bureau of Mineral Resources drill-hole Urapunga 5. Herein, we establish that the SHRIMP sample originated from the type locality of the Derim Derim Dolerite in outcrop 90 km northwest of Urapunga 5 and document the ²⁰⁷Pb/²⁰⁶Pb date interpreted from the 1997 dataset. New U–Pb SHRIMP reanalysis of the same grain-mounts yielded a mean ²⁰⁷Pb/²⁰⁶Pb date of 1320.1 ± 5.3 Ma, confirming the 1997 result, and isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) analysis of baddeleyites plucked from the mounts yielded a precise mean ²⁰⁷Pb/²⁰⁶Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U–Pb ID-TIMS date of ca 1313 Ma recently reported elsewhere from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Previously documented geochemical variation in Mesoproterozoic intraplate mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma Galiwinku Dolerite in the McArthur Basin, 1316 ± 40 Ma phonolites in the Nimbuwah Domain of the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. The timing and geochemistry of Derim Derim-Galiwinku mafic igneous activity is strikingly similar to that of the Yanliao Large Igneous Province (LIP) in the northern North China Craton, and the global paucity of 1330–1300 Ma LIPs suggests that the North Australian Craton and the North China Craton were in relatively close proximity at that time.
• KEY POINTS
• We document a previously unpublished U–Pb baddeleyite date of 1324 ± 4 Ma for the Derim Derim Dolerite in the McArthur Basin, obtained via sensitive high-resolution ion micro probe (SHRIMP), and substantiate it with an isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) date of 1327.5 ± 0.6 Ma from the same sample.
• Our dates are significantly older than a U–Pb baddeleyite ID-TIMS date of ca 1313 Ma from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma.
• Contemporaneous intraplate mafic magmatism extended hundreds of kilometres across the Northern Territory, spanning the Tomkinson Province, the McArthur Basin, and the Nimbuwah Domain of the eastern Pine Creek Orogen.
• The timing and geochemistry of Derim Derim Dolerite magmatism strongly resembles the Yanliao Large Igneous Province (LIP) in the northern North China Craton, which suggests that the North Australian Craton and the North China Craton were in close proximity during the Mesoproterozoic.
... It is believed that these rocks were accreted to the Yilgarn Craton 1345-1260 Ma ago [56]. Development of the Fraser zone in a convergent setting led to formation of the Fraser Complex during the Middle Mesoproterozoic (1300 Ma [17]), but the majority of convergencerelated magmatic rocks are presumably concentrated within the buried Madura Province, where, among other things, the Loongana Arc, with an age of ca. 1410 Ma, was located [34], and the Coompana Province, where the age of juvenile rocks ranges from 1610 to 1500 Ma [22,55]. ...
An assemblage of mafic granulites (schists), plagiogneisses, and metasedimentary rocks, which is referred to as the Filla Series, is exposed in the Rauer Islands (opposite the eastern coast of the Prydz Bay). The chemistry and Nd isotope composition of the schists, which are interpreted as metavolcanics, are characterized ; the results of U-Th-Pb dating (SHRIMP) of zircons from these rocks are presented. The data obtained indicate that the protolith of these rocks crystallized ca. 1500 Ma ago and that the rocks later underwent thermal events at ca. 1000 Ma and 545-515 Ma. The relatively high ε Nd (t) values, ranging from 2 to 4.5 for most samples, indicate the primitive composition of the mantle source and the limited extent of crustal contamination. The specific chemical composition of these rocks suggests that the Filla Series was formed in a convergent (back-arc(?)) setting with contributions from both plume and lithospheric sources. The apparently heterogeneous rock assemblage may be a product of tectonic interaction between the active continental margin and oceanic plateau. The obtained Early Mesoproterozoic age of the mafic rocks of the Filla Series argues for correlation of the Rauer Islands area with the long-lived Musgrave-Albany-Fraser-Wilkes Pro-terozoic (super) province in Australia and Antarctica, on the one hand, and the Eastern Ghats Province in India, on the other. The formation of the Early Mesoproterozoic Filla Series suggests that the development of the hypothetical paleocean (its convergent margins) did not terminate during the Paleoproterozoic but continued into the Mesoproterozoic. Correlation with the Musgrave-Albany-Fraser-Wilkes (super) province suggests a shared geological evolution of large crustal blocks, represented by the Prydz Bay coast and the Australian-Antarctic block starting from the Early Mesoproterozoic.
... It is believed that these rocks were accreted to the Yilgarn Craton 1345-1260 Ma ago [56]. Development of the Fraser zone in a convergent setting led to formation of the Fraser Complex during the Middle Mesoproterozoic (1300 Ma [17]), but the majority of convergencerelated magmatic rocks are presumably concentrated within the buried Madura Province, where, among other things, the Loongana Arc, with an age of ca. 1410 Ma, was located [34], and the Coompana Province, where the age of juvenile rocks ranges from 1610 to 1500 Ma [22,55]. ...
... Within the Fraser Zone, the timing of emplacement and metamorphism of the volumetrically dominant (meta)gabbroic rocks is poorly constrained compared to the history of the metasedimentary and granitic units (Clark et al., 1999;De Waele andPisarevsky, 2008, Kirkland et al., 2011b). In an effort to resolve this situation, this study integrates phase equilibria modelling and in situ U-Pb isotopic dating of the (meta)gabbros to better constrain the P-T-t history of the Fraser Zone and elucidate the tectonic setting in which they may have formed. ...
... Primary magmatic textures in the isolated grain leads to an interpretation that the Concordia age of 1296 ± 5 Ma (2σ, MSWD = 1.3) dates the magmatic crystallisation of the gabbro (Fig. 3). This age overlaps with the magmatic age of a charnockite (1301 ± 6 Ma; Clark et al., 1999) and an age of c. 1291 ± 8 Ma from a mafic granulite (De Waele and Pisarevsky, 2008), both from the Fraser Zone. ...
The Fraser Zone is a major lithotectonic domain of the Albany–Fraser Orogen, Western Australia, which records Proterozoic modification of the margin of the Archean Yilgarn Craton. The Fraser Zone is volumetrically dominated by gabbroic rocks and their metamorphosed equivalents. However, little is known of the pressure–temperature–time (P–T–t) history or the geodynamic setting of these mafic rocks. When considered within the context of existing P–T constraints from spatially-associated metapelitic rocks, modelled phase equilibria suggest that both the unmetamorphosed gabbros and the granulite facies metagabbroic rocks equilibrated at 950–900 °C and ∼7 kbar, interpreted to record the conditions of magmatic crystallisation and peak metamorphism, respectively. These data support the view that mafic magmatism was the thermal driver for high-T, low-P granulite facies metamorphism. The absence of garnet from the metagabbroic rocks, and the lack of evidence for its former presence (i.e., as inclusions), argues that, during metamorphism, the rocks never reached pressures above those they attained at the thermal peak. Coronæ of zircon around ilmenite in the magmatic rocks reflect a local supply of Zr as it exsolved from ilmenite, permitting earlier growth of zircon around ilmenite than elsewhere during melt crystallisation. U–Pb dating of coronal zircon (1315 ± 5 Ma) and a discrete magmatic zircon grain isolated from ilmenite (1296 ± 5 Ma) constrain the duration of magmatic crystallisation between ca. 10 and 30 Ma. Zircon in a metamorphosed gabbro constrains the timing of granulite facies metamorphism to 1293 ± 6 Ma, synchronous with final crystallisation of the mafic magmas. Based on the implied metamorphic evolution of these rocks and that of the surrounding supracrustal package, along with existing isotopic and geochemical data, we suggest the Fraser Zone probably formed in a backarc, or perhaps an intracontinental rift setting, and records successive emplacement of gabbroic rocks into a thick, sediment-filled basin. The older gabbroic rocks record hydration and reaction with the devolatilising and/or partially molten metasedimentary rocks into which they were emplaced. Subsequent granulite facies metamorphism of these hydrated rocks was driven by the heat provided by the intrusion of younger mafic magmas.
... 1305(ca. -1290Clark et al., 1999;De Waele and Pisarevsky, 2008;Smithies et al., 2013), and felsic protoliths to the Clark Peninsula orthogneiss (ca. 1315 Ma) in the Windmill Islands (Morrissey et al., 2017b;Zhang et al., 2012). ...
We present LA–ICP–MS U–Pb monazite and zircon geochronology, trace element chemistry and phase equilibria forward modelling to constrain the P–T–t evolution of the Bunger Hills, East Antarctica. Metasedimentary rocks in the Bunger Hills record evidence for a protracted metamorphic history during the Mesoproterozoic. Taken in isolation, zircon and monazite ages suggest an extremely long duration of high-temperature conditions (ca. 200 Myr). Calculated P–T models indicate metamorphism involved medium pressures of 5.5–7.1 kbar and high to ultrahigh temperatures of 800–960 °C, and that the P–T path likely tracked along a down-pressure to isobaric cooling trajectory. Integrating trace element data from zircon, monazite and garnet indicates that, despite the spread in U–Pb ages, peak metamorphism essentially occurred over the interval ca. 1220–1180 Ma. The age and conditions of Mesoproterozoic metamorphism are consistent with the high-grade metamorphic evolution proposed previously for Stage-2 of the Albany–Fraser Orogeny in southwestern Australia. The P–T–t conditions are interpreted to reflect extension, potentially associated with unloading and exhumation of a collisional orogen following Stage-1 of the Albany–Fraser Orogeny. This is the first study to integrate geochronology, trace element chemistry and P–T modelling to constrain the metamorphic evolution of the Bunger Hills and to interpret these constraints within the context of the now separate terranes of the Musgrave–Albany–Fraser Orogen. The three-way approach adopted in this study demonstrates that zircon and monazite may grow and modify through a number of processes. An integrated petrochronologic approach is therefore essential for investigations on high-grade terranes.
... 1283 Ma, shortly after deposition of the Arid Basin Waddell et al., 2015). Magmatic crystallization of mafic intrusive rocks in the Fraser Zone has been dated at 1299 ± 3 Ma, 1299 ± 10 Ma, and 1291 ± 8 Ma (Clark et al., 1999;De Waele and Pisarevsky, 2008;Kirkland et al., 2011a). High-grade metamorphism occurred at c. 1290 Ma soon after deposition of the Snowys Dam Formation. ...
The U–Pb isotopic signature of titanite collected across an exhumed refractory lower crustal block within the Albany–Fraser Orogen, Australia, records thermal overprints not apparent in a suite of other U–Pb chronometers. This helps to reconcile a dichotomy within the geochronological record of two adjacent zones within the orogen. The zircon U–Pb record for the older Biranup Zone preserves widespread overprinting at 1225–1140 Ma (Stage II), whereas the younger Fraser Zone records an older 1330–1260 Ma (Stage I) tectonothermal event. Titanite in the Fraser Zone also predominantly records a U–Pb age of 1299 ± 14 Ma, reflecting the interval of closure to radiogenic Pb mobility. Nonetheless, small titanite grains reveal subsequent overprinting with a mean reset age of 1205 ± 16 Ma. By contrast, titanite from metasedimentary rocks within the adjacent Biranup Zone principally record U–Pb ages of 1200–1150 Ma, interpreted as dating cooling after prolonged Stage II metamorphism. Interestingly, titanite also preserves domains with old apparent ages. These domains have a statistically significant association with lower U content and also indicate reduced Sm/Yb ratios and are interpreted to have lost U but acquired HREE (e.g. Yb) more rapidly than MREE (e.g. Sm). The old apparent ages are interpreted as artefacts of a Stage II U redistribution process, leading to unsupported radiogenic Pb. In addition, titanite grain size has a strong effect on the preservation or resetting of metamorphic U–Pb ages. Thermochronological modelling based on apparent age versus grain size relationships indicates that complete resetting of small titanite grains requires overprinting temperatures of 695–725 °C during Stage II in the Fraser Zone. This result is similar to estimates from the Biranup Zone based on phase equilibrium modelling that indicates pressures and temperatures of 6.5–8.5 kbar and 675–725 °C. An in situ U–Pb analysis strategy for titanite that targets a range of grain sizes has the potential to reveal differential resetting and place important controls on thermal history.
... The evidence for recent Pb loss (and the general tendency for this to occur in Archean zircons) leads us to interpret this date as a minimum age for an event that caused localized loss of radiogenic Pb. The obvious candidate is some aspect of the formation of the Fraser zone, at ~1300 Ma (Fletcher et al., 1991;Clark et al., 1999;De Waele and Pisarevsky, 2008). ...
Gold mineralization at the Tropicana mine occurs within the Plumridge terrane along the eastern margin of the Archean Yilgarn craton in the Albany-Fraser orogen, Western Australia. Mineralization is hosted in a favorable syenitic lithofacies of the Tropicana Gneiss with a minimum igneous age of 2638 ± 4 Ma (2σ) and which was metamorphosed to mid-amphibolite to lower granulite facies in the period ca. 2638 to 2520 Ma. The Tropicana Gneiss was exhumed to crustal levels equivalent to greenschist-facies conditions by the time of economic gold mineralization. The major gold-bearing pyrite-biotite-sericite mineralization formed in association with shear zones during northeast-southwest compression (D3) that postdated W- to NW-verging thrusting (D2). The late fluid-induced event (Tropicana event; Doyle et al., 2013; Blenkinsop and Doyle, 2014) produced a mineral assemblage indicative of greenschist-facies conditions. The paucity of water in granulite-facies gneisses under retrograde conditions suggests that fluids were introduced from an external source for both mineralization and the younger metamorphic event. This occurred at ca. 2520 Ma as determined from biotite (ca. 2515 Ma, 40Ar/39Ar age), pyrite (ca. 2505 Ma, Re-Os, Pb/Pb ages), and tungsten-rich rutile (2521 ± 5 Ma, U-Pb age): the latter is considered to provide the best direct measurement age of gold mineralization. The Tropicana Gneiss was derived from the upthrusted easternmost margin of the underlying Yilgan craton, or represents a relatively small (160 km long × 50 km wide) remnant crustal block accreted to the Yilgarn craton sometime between ca. 2.6 and 2.5 Ga. The timing of the Tropicana mineralization is distinctly younger than greenstone-associated gold deposits elsewhere in the Yilgarn craton. As in the Dharwar craton, India, and the Limpopo belt, Zimbabwe, economic gold mineralization at Tropicana postdates the major peak of Late Archean world-class gold mineralization (ca. 2.65 Ga) by more than 100 m.y. The Tropicana Gneiss was relatively unaffected during the younger Albany-Fraser orogeny, with only minor remobilization of gold. Deformation may have been localized at the margins of the domain, between constituent ridged structural blocks, and/or within discrete high-strain shears.
... The northeasterly trending Fraser Zone contains the c. 1300 Ma Fraser Range Metamorphics (Spaggiari et al., 2009), a suite of interleaved thin slivers of granitic gneiss, metasedimentary rocks, and mafic rocks, that are now mostly pyroxene granulites or mafic amphibolites (Fig. 2;Myers, 1985;Clark et al., 1999;De Waele and Pisarevsky, 2008;Spaggiari et al., 2009). Myers (1985) interpreted the mafic rocks in the Fraser Zone as part of a large layered mafic intrusion, whereas Condie and Myers (1999) argued that they represent remnants of multiple magmatic arcs. ...
... Boundaries between the rock units were previously interpreted to be major thrust faults that interleaved slivers of older 'basement' gneiss and metasedimentary rocks with the mafic rocks (Myers, 1985). However, it is now known that the granitic and metasedimentary rocks previously interpreted as 'basement' are similar in age to the mafic rocks (Clark et al., 1999;De Waele and Pisarevsky, 2008; this study). Kinematic indicators and aeromag-netic data indicate a significant dextral shear component along the northwestern edge of the Fraser Zone, defined by the Fraser Fault, which separates the Biranup Zone from Fraser Zone rocks (Fig. 2). ...
... Crystallization of gabbro within the Fraser Zone is dated at 1291 ± 8 Ma (De Waele and Pisarevsky, 2008) by U-Pb on zircon and at 1291 ± 21 Ma by a whole-rock Sm-Nd isochron (MSWD = 0.25; (Fletcher et al., 1991). A minimum age constraint on the mafic rocks is provided by an intrusive charnockitic orthogneiss cutting the gabbros at 1301 ± 6 Ma (Clark et al., 1999). ...
The Albany-Fraser Orogen is considered to be a response to Mesoproterozoic continent–continent collision between the combined North and West Australian Cratons and the combined East Antarctic and South Australian Cratons. However, the tectonic history of the orogen and its components remain enigmatic. Recently, the Kepa Kurl Booya Province has been defined as the crystalline basement of the orogen and divided into the Fraser, Biranup, and Nornalup Zones. New geochronology shows that the Biranup Zone includes 1710–1650 Ma granitic to gabbroic intrusions and is a substantial crustal component extending at least 1200 km along the southern and southeastern margins of the Yilgarn Craton. Previous models interpreted the Biranup Zone as an exotic terrane accreted to the Yilgarn Craton during Mesoproterozoic collision, but new data presented here indicate a strong link to the craton margin during the Paleoproterozoic.
... In the eastern Biranup Zone, folded (pre-tectonic) and cross-cutting (post-tectonic) leucosomes constrain the timing of northeast–southwest compression to c. 1680 Ma, which is defi ned as the Zanthus Event (Kirkland et al., 2011). The near-coeval sedimentation, deformation, and magmatism, together with the chemistry of these rocks which plot within the ' The c. 1300 Ma Fraser Range Metamorphics (Spaggiari et al., 2009) are a series of interleaved slivers of granitic gneiss, metasedimentary rocks, and mafi c gabbroic rocks, now mainly pyroxene granulites (Clark et al., 1999; De Waele and Pisarevsky, 2008; Myers, 1985) (Fig. 3). Boundaries between the rock units were previously interpreted to be major thrust faults that interleaved older 'basement' gneiss and metasedimentary rocks with mafi c rocks (Myers, 1985). ...
... Boundaries between the rock units were previously interpreted to be major thrust faults that interleaved older 'basement' gneiss and metasedimentary rocks with mafi c rocks (Myers, 1985). However, it is now known that the granitic and metasedimentary rocks are similar in age to the mafi c rocks (Clark et al., 1999; De Waele and Pisarevsky, 2008). Myers (1985) interpreted the mafi c rocks in the Fraser Zone as part of a large layered mafi c intrusion, whereas Condie and Myers (1999) argued that they represent remnants of multiple magmatic arcs. ...
