Figure 2
(A) Individual δ 18 O values of zircon from Zealandia plutonic rocks from the eastern and western isotope domains. Black symbols are δ 18 O zircon values from plutonic rocks of the South China block (Fu et al., 2013). VSMOW-Vienna standard mean ocean water. (B) Individual zircon ε Hf(t) values for Zealandia plutonic rocks. Median δ 18 O and ε Hf(t) for each domain is represented by colored vertical bar; line thickness represents 1σ uncertainty (±0.15‰ for δ 18 O; ±0.7 for ε Hf(t) ). Analyses interpreted as metamorphic and inherited (based on spot U-Pb age) are not plotted. Samples (n = 169) analyzed in this study are supplemented with 61 additional δ 18 O and ε Hf(t) values from Hiess et al. (2015), van der Meer et al. (2018), Schwartz et al. (2021).
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We present a data set of >1500 in situ O-Hf-U-Pb zircon isotope analyses that document the existence of a concealed Rodinian lithospheric keel beneath continental Zealandia. The new data reveal the presence of a distinct isotopic domain of Paleozoic–Mesozoic plutonic rocks that contain zircon characterized by anomalously low δ18O values (median = +...
Contexts in source publication
Context 1
... east of the limit of Paleozoic metasedimentary rocks have consistently low δ 18 O values (Figs. 1B and 2A), with most within ±1‰ of the median δ 18 O value of +4.1‰ (a range from −8.1‰ to +8.9‰). Plutonic rocks are Carboniferous to Cretaceous, with whole-rock SiO 2 from 50 to 77 wt%. Low intrasample δ 18 O variability for most granitoid samples ( Fig. 2A) supports isotopic homogenization in high-temperature melt-rich systems (Figs. 1B and 2A). This contrasts with plutonic rocks emplaced in the western isotope domain (WID), which have mantle and crustal δ 18 O values and almost no plutonic rocks with δ 18 O zircon values ...
Context 2
... into the source(s) for the low-δ 18 O EID come from considering zircon Hf isotope compositions. Plutonic rocks from the low-δ 18 O EID have more radiogenic ε Hf(t) values (median ε Hf(t) = +6.1) and are tightly clustered compared to those emplaced in the WID (median ε Hf(t) = +1.9, broad range of values) (Fig. 2B). Coupled O-Hf zircon isotope compositions indicate that plutonic rock compositions from the low-δ 18 O EID were controlled by melting of a relatively isotopically homogeneous mafic lower-crustal source (radiogenic ε Hf(t) values) that had experienced high-temperature hydrothermal alteration (responsible for the low-δ 18 O signature). ...
Context 3
... propose that Phanerozoic plutonic rocks emplaced within the low-δ 18 O EID of Zealandia were produced by partial melting of a hydrothermally altered Precambrian lower-crustal mafic source. This accounts for calculated crustal residence ages between ca. 1300 and 500 Ma, radiogenic ε Hf(t) , and low δ 18 O zircon values ( Fig. 2; Figs. S3 and S4). A three-stage process is evoked to explain the formation and subsequent alteration of the lower-crustal Precambrian source. In the first stage, melting of depleted mantle between ca. 1300 and 900 Ma produced mafic melts that ponded at the base of the crust. Magmatism during this period occurred along an active oceanic ...
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We provide the results of studying the internal structure and composition of the rocks of the Semeitau and Delbegetei massifs located in Eastern Kazakhstan. It was previously believed that these massifs have different ages and were formed in different geodynamic settings. The U-Pb zircon age from the monzonites and quartz monzonites was determined...
Citations
... A distinguishing feature of these Lachlan Orogen zircons is the significant amount of <1050 Ma zircon, these are more characteristic of parts of East Antarctica such as the Tonian Oceanic Arc Super Terrane (TOAST, Jacobs et al., 2015 and the Rayner Complex (Fitzsimons, 2000). The South Tasman Rise (Figure 1) is another possible source for late Mesoproterozoic to early Neoproterozoic zircon (Berry et al., 2008;Fioretti et al., 2005), as is the hypothesised Precambrian keel of Zealandia (Adams and Campbell, 2023;Adams and Ramsay, 2022;Turnbull et al., 2021). U-Pb DZ ages from the Myrtle Springs Formation, the Mitcham Quartzite, and the Gilbert Range Quartzite samples appear to support an influx of younger, more exotic detritus ( Figure 6). ...
Late Tonian sequences of the Adelaide Superbasin were witness to the birth of the proto-Pacific Ocean during the breakup of Rodinia. Understanding the sedimentology and provenance of these rocks from across the basin is key to understanding their deposition over c. 70 million years, the local palaeogeography, and leads to a better understanding of the early development of the proto-Pacific Ocean. While the sedimentology of the Burra Group is well studied in most areas, provenance studies on these sequences using detrital zircon have been limited in scope and lack both spatial and temporal diversity. We begin to address this knowledge gap. Samples were taken from across the Adelaide Superbasin to understand both spatial and temporal related changes in provenance. Our findings highlight the necessity of this approach by uncovering both subtle, and abrupt significant changes in detrital zircon spectra for coeval samples from across the basin, and up-sequence in local areas. Our results highlight significant changes in provenance c. 790 Ma in the north of the basin, and c. 740 Ma in the south of the basin. This suggests a southward advancement of the rift basin, gradually opening to southerly sediment supply. We posit the existence of an unrecognised source of c. 1000–900 Ma zircon to the north or northeast of the basin to account for latest Stenian to earliest Tonian detrital zircon in the Myrtle Springs Formation. Additionally, we explore the comparison of coeval Tasmanian and Laurentian sequences, suggesting a stronger Australia-Tasmania link than Tasmania-Laurentia as time progresses.
... Zircon U-Pb geochronology by CA-(chemical abrasion) ID-TIMS was done at the Massachusetts Institute of Technology Isotope Laboratory following procedures described in Ramezani et al. (2022). Zircon O-isotope analysis at the Universität Heidelberg and zircon Lu-Hf isotope analysis at Curtin University were undertaken by secondary ion mass spectrometry and multi-collector LA-ICP-MS respectively, according to procedures documented in Turnbull et al. (2021). All U-Pb age calculations and statistical assessment of detrital zircon populations were completed using Isoplot software (Ludwig, 2008 Ar-Ar dating was done at the United States Geological Survey, Menlo Park following procedures in Calvert and Lanphere (2006); Ar-Ar ages in this paper are reported relative to a Fish Canyon sanidine age of 28.198 Ma (i.e., they are compatible with Gans et al. (2023)). ...
New rock dredge samples supply key information to establish the tectonic and geological framework of the northern two‐thirds of the 95% submerged Zealandia continent. The R/V Investigator voyage IN2016T01 to the Fairway Ridge, Coral Sea, obtained poorly sorted poly‐lithologic pebbly to cobbly sandstones, well sorted fine grained sandstones, mudstones, bioclastic limestones, and basaltic lavas. Post‐cruise analytical work comprised petrography, whole rock geochemical and Sr and Nd isotopic analyses, and U‐Pb zircon, Rb‐Sr, and Ar‐Ar geochronology. A Fairway Ridge cobbly sandstone has a ∼95 Ma (early Late Cretaceous) depositional age; two biotite granite cobbles are 111 ± 1 and 128 ± 1 Ma in age, and some volcanic pebbles are also likely Early Cretaceous. Fairway Ridge basalts have intraplate alkaline chemistry and are of Late Eocene age (∼40–36 Ma). By analogy with South Zealandia, we interpret strong positive continental magnetic anomalies of North Zealandia to mainly result from Late Cretaceous to Cenozoic intraplate basalts, many of them rift‐related lavas. A new basement geological map of North Zealandia shows the position of the Mesozoic Gondwana magmatic arc axis (Median Batholith) and other major geological units. This study completes onland and offshore reconnaissance geological mapping of the entire 5 Mkm² Zealandia continent.
... Magmas generated and emplaced within the continental crust are considered to primarily be the result of partial melting of the mid-lower continental crust with variable contributions from juvenile mantle-derived melts (e.g., Barbarin 1999;Annen et al. 2006;Kemp et al. 2007;Frost and Frost 2011;Brown 2013). The trace element and isotopic composition of zircon can therefore be used to determine the mantle source and the age and composition of the crustal rock(s) that melted in the mid-lower crust to form the initial magmas (Belousova et al. 2002;Kemp et al. 2007; Mole et al. 2014;Roberts and Spencer 2015;Decker et al. 2017;Johnson et al. 2017;Osei et al. 2021;Schwartz et al. 2021;Turnbull et al. 2021). In combination with 206 Pb-238 U zircon dating, this geochemical information can also be used to assess the processes involved in the subsequent evolution of magmas Bolhar et al. 2008;Davies et al. 2021). ...
... Our dataset utilizes in-situ 206 Pb-238 U, Lu-Hf and d 18 O values of zircon from 266 plutonic rocks throughout Zealandia. This dataset includes new analyses completed for 169 samples as part of this study ( 206 Pb-238 U, O and Hf isotope data initially presented in Turnbull et al. 2021), supplemented with d 18 O values 206 Pb-238 U ages and Lu-Hf data from an additional 95 samples from published (Bolhar et al. 2008;Scott et al. 2009;Turnbull et al. 2013;Hiess et al. 2015;Milan et al. 2016;van der Meer et al. 2018;Decker et al. 2017;Schwartz et al. 2021) and unpublished studies (Decker 2016, Turnbull unpublished). We produce a series of multiisotopic contour maps, from which we interpret the age and composition of Zealandia's lithosphere through space and time. ...
... Previous studies indicate these shear zones represent major crustal boundaries, separating blocks with distinct differences in lithology, zircon inheritance, whole-rock isotopic signature and metamorphic grade (Tulloch and Kimbrough, 2003;Marcotte et al. 2005;Allibone and Tulloch 2008;Scott et al. 2009;Klepeis et al., 2022). Recent comprehensive zircon isotope studies that transect these shear zones confirm they represent major crustal structures, with distinct isotopic domains occurring on either side of them Turnbull et al. 2021). The Eastern Isotope Domain (EID) occurs to the east of this boundary and is characterized by plutons emplaced between c. 374 -120 Ma with remarkably homogeneous light d 18 O values and radiogenic e Hf(t) zircon compositions Turnbull et al. 2021). ...
... The recognition of the possible occurrence of a Precambrian supercontinent over 40 years ago (Bell and Jefferson, 1987;McMenamin and McMenamin, 1990;Nance et al., 1988) and subsequent rapid developments in the reconstruction of both the Neoproterozoic supercontinent Rodinia (e.g., Dalziel, 1991;Hoffman, 1991;Li et al., 2008a;Moores, 1991) and the Paleo-(?) to Mesoproterozoic supercontinent Nuna/Columbia (Evans and Mitchell, 2011;Meert, 2002;Pisarevsky et al., 2014a;Rogers and Santosh, 2002;Zhang et al., 2012b;Zhao et al., 2002) brought an explosion of knowledge in Precambrian geotectonic and palaeogeographic evolution. In particular, the rapid realisation of the likely cyclic occurrence of supercontinents in Earth history (Evans et al., 2016a;Nance et al., 1988), together with the seismic tomographic discoveries of both whole-mantle convection (van der Hilst, 2004;van der Hilst et al., 1997) and large lower mantle structures such as the large low-shear-velocity provinces (LLSVPs; Dziewonski, 1984), and the temporal and spatial linkages between supercontinent events and global plume episodes (Evans, 2003;Li et al., 2003Li et al., , 2004Li and Zhong, 2009), enabled the geoscience community for the first time to develop holistic global geodynamic models that link plate tectonics with global-scale mantle convection, first order mantle structures, and mantle plume generation (Li et al., 2008a;Li and Zhong, 2009;Maruyama, 1994;Zhong et al., 2007) with the latter being dramatically expressed in the Large Igneous Province record (Coffin and Eldholm, 1994;Ernst and Buchan, 2003). Although lithosphere-whole mantle coupled global geodynamic models are still in their early days and competing models exist (e.g., Burke et al., 2008;Dziewonski et al., 2010;Torsvik et al., 2008b;Torsvik et al., 2014), numerous subsequent geodynamic modelling and geochemical works (Doucet et al., 2020a;Doucet et al., 2020b;Gamal El Dien et al., 2019) have demonstrated that first-order mantle structure may indeed have coupled with the supercontinent cycle since 2 Ga. ...
... 1000-900 Ma orogens and sutures between Australia-East Antarctica and Laurentia to account for the geological disconnections prior to 900 Ma (Borg and DePaolo, 1994) and palaeomagnetic evidence that argues against the existence of any SWEAT-like connection during 1200-1050 Ma Wingate et al., 2002), (3) tectono-stratigraphic correlations of the rift-to-drift record (Brennan et al., 2021b;Li et al., 1995;Powell et al., 1994;Ross, 1991), and (4) mantle plume records of 825-720 Ma LIPs leading to the rifting and eventual break-up of Rodinia (Li et al., 1999(Li et al., , 2008a. The central location of South China in Rodinia, based on these evidences as well as our current palaeomagnetic analysis (see 4.2.1 below), has been challenged by numerous studies (e.g., Cawood et al., 2013;Chang et al., 2022;Merdith et al., 2021), but supported by others (Turnbull et al., 2021;Zou et al., 2021). Future verifications of the various competing Rodinia reconstruction models will critically depend on the availability of more high-quality palaeomagnetic poles from all major continents (see below). ...
Establishing how tectonic plates have moved since deep time is essential for understanding how Earth’s geodynamic system has evolved and operates, thus answering longstanding questions such as what “drives” plate tectonics. Such knowledge is a key component of Earth System science, and has implications for wide ranging fields from core-mantle-crust interaction and evolution, geotectonic phenomena such as mountain building and magmatic and basin histories, the episodic formation and preservation of Earth resources, to global sea-level changes, climatic evolution, atmospheric oxygenation, and even the evolution of life. In this paper, we take advantage of the rapidly improving database and knowledge about the Precambrian world, and the conceptual breakthroughs, both regarding the presence of a supercontinent cycle and possible dynamic coupling between the supercontinent cycle and mantle dynamics, in order to establish a full-plate global reconstruction from 540 Ma back to 2000 Ma. We utilise a variety of global geotectonic databases to constrain our reconstruction, and use palaeomagnetically recorded true polar wander events and global plume records to help evaluate competing geodynamic models and also provide new constraints on the absolute longitude of continents and supercontinents. After revising the configuration and life span of both supercontinents Nuna (1600—1300 Ma) and Rodinia (900—720 Ma), we present a 2000—540 Ma animation, starting from the rapid assembly of large cratons and supercratons (or megacontinents) between 2000 Ma and 1800 Ma. This occurred after a billion years of dominance by small cratons, and kick-started the ensuing Nuna and Rodinia supercontinent cycles and the emergence of stable, hemisphere-scale (long-wavelength) degree-1/degree-2 mantle structures. We further use the geodynamicly-defined type-1 and type-2 inertia interchange true polar wander (IITPW) events, which likely occurred during Nuna (type-1) and Rodinia (type-2) times as shown by the palaeomagnetic record, to argue that Nuna assembled at about the same longitude as the latest supercontinent Pangaea (320—170 Ma), whereas Rodinia formed through introversion assembly over the legacy Nuna subduction girdle either ca. 90◦ to the west (our slightly preferred model) or to the east before the migrated subduction girdle surrounding it generated its own degree-2 mantle structure by ca. 780 Ma. Our interpretation is broadly consistent with the global LIP record. Using TPW and LIP observations and geodynamic model predictions, we further argue that the Phanerozoic supercontinent Pangaea assembled through extroversion on a legacy Rodinia subduction girdle with a geographic centre at around 0◦E longitude before the formation of its own degree-2 mantle structure by ca. 250 Ma, the legacy of which is still present in present-day mantle.
(the paper is of OPEN ACCESS at http://dx.doi.org/10.1016/j.earscirev.2023.104336)
... Inside the Median Batholith, a major structural and isotopic boundary separates outboard (eastern) and inboard (western) belts, marking the eastern limit of the late Paleozoic Gondwana margin (Allibone, Jongens, Scott, et al., 2009;Milan et al., 2017;Mortimer, Gans, et al., 1999;Scott et al., 2011;Tulloch & Kimbrough, 2003;Figures 2 and 3). Turnbull et al. (2021) and Schwartz et al. (2021) showed that this boundary likely extends into the mantle lithosphere where it separates distinctive isotopic domains. Minor Devonian plutons only occur west of the boundary. ...
... Three subvertical boundaries (3, 4, and 5) coincide with the Grebe-IC, George Sound (GSSZ), and Straight River (SRSZ) shear zones, respectively. Graph at the bottom shows that two of the vertical boundaries coincide with isotopic zones in the lithospheric mantle (after Schwartz et al., 2021;Turnbull et al., 2021): WID; western isotopic domain, CID; central isotopic domain, EID; Eastern isotopic domain. References: 1. this study, 2. Buriticá et al. (2019), 3. Bhattacharya et al. (2018), 4. Stowell et al. (2017), 5. Schwartz et al. (2017), 6. Milan et al. (2016), 7. Klepeis et al. (2016), 8. Scott et al. (2009), 9. Ramezani and Tulloch (2009), 10. ...
... Fiordland also exhibits three vertical boundaries (Figure 7) of Carboniferous origin. The eastern boundary coincides with the Grebe-IC shear zone and marks the late Paleozoic edge of Gondwana (Figure 3b; Marcotte et al., 2005;McCoy-West et al., 2014;Scott et al., 2011;Turnbull et al., 2021). To the west, linear belts of late Carboniferous plutons and high-strain zones define two other boundaries : the George Sound (GSSZ) and Straight River (SRSZ) shear zones (Figures 4 and 7). ...
Structural analyses combined with new U‐Pb zircon and titanite geochronology show how two Early Cretaceous transpressional shear zones initiated and grew through a nearly complete section of continental arc crust during oblique convergence. Both shear zones reactivated Carboniferous faults that penetrated the upper mantle below Zealandia's Median Batholith but show opposite growth patterns and dissimilar relationships with respect to arc magmatism. The Grebe‐Indecision Creek shear zone was magma‐starved and first reactivated at ∼136 Ma as an oblique‐reverse fault, along which an outboard batholith partially subducted beneath Gondwana. This system nucleated at or above ∼20 km depth and propagated downward at 2–3 mm yr⁻¹, accumulating at least 35–45 km of horizontal (arc‐normal) shortening by ∼124 Ma. In contrast, the magma‐rich George Sound shear zone first reactivated in the lower crust (∼55 km depth) at ∼124 Ma and grew upward at ∼3 mm yr⁻¹, reaching the upper crust by ∼110 Ma. In this latter system, magmatism influenced shear zone architecture and drove its growth while subduction and oblique convergence ended. As magma entered the roots of the system and began to solidify, deformation was driven out of the lower crust and into the middle crust where the system widened by a factor of three when fold‐thrust belts formed on either side of a steep, central transpressional shear zone. This study illustrates how the reactivation of structural weaknesses localizes deformation at all depths in the lithosphere and shows how magma‐deformation feedbacks influence shear zone connectivity and built a batholith from the bottom up.
... The majority of the Archean grains in the HAUR1, 2 and TAK1, 2 datasets are euhedral and thus unlikely to be far travelled and/or multiply recycled. A Mesoproterozoic (RA) and late Neoproterozoic (GA) basement block has been proposed in south Zealandia that, again on indirect evidence, was exposed as a continental hinterland in the early Paleozoic (Adams et al., 2015;Adams & Griffin, 2012;Turnbull et al., 2021), but the idea of an older, Nuna (Columbia) supercontinent nucleus within it has remained speculative (Adams et al., 2015). This introduces the possibility that the eastern margin of the Takaka Terrane was not an ocean margin to a Rodinia supercontinent block to the west but rather, in the early Paleozoic, was juxtaposed to a different sector of the Rodinia supercontinent to the north or east that also has Archean and Paleoproterozoic nuclei. ...
... However, with the later recognition of Zealandia as a continent in its own right (Mortimer et al., 2017), and with a Precambrian lithospheric mantle keel (Turnbull et al., 2021), attention turned to the possibility that sources for lower Paleozoic sediments might instead be within Zealandia itself (Adams et al., 2015;Adams & Griffin, 2012). However, a Mesoproterozoic connection between Zealandia and the South China Block still remains very plausible, as detrital zircon sources in their lower Paleozoic sedimentary rocks display a common Rodinia heritage and even older similar Archean and Paleoproterozoic connections. ...
Detrital zircon age patterns are reported from quartz sandstones and metaquartzites in the Russet and Wangapeka formations (Western Province, Takaka Terrane) in Fiordland and northwest Nelson, and the Pegasus Group on Stewart Island. The latter indicate a possible maximum early Carboniferous depositional age with a significant Lower Devonian zircon component that suggests a source on the Campbell Plateau or Marie Byrd Land, West Antarctica. In contrast, Russet Formation ages indicate a correlation with Upper Ordovician, Wangapeka Formation quartz sandstones in northwest Nelson. These zircon age patterns have two major groups: late Mesoproterozoic (1200–1000 Ma) of Rodinia origin and Cambrian–late Neoproterozoic (700–500 Ma) of early Gondwana derivation. Both groups have local Zealandia provenances. In addition, there are unusually high proportions (to 20%) of early Paleoproterozoic and Archean zircons, 3500–2000 Ma, with significant age components, 2550–2450 Ma and ca 2800 and 2650 Ma, which are characteristic of an Expanded-Ur continent. Their high proportions of euhedral grains indicate a local source within a postulated Archean basement block at or near the eastern margin of the Takaka Terrane. A proposed Rodinia supercontinent reconstruction locates this Precambrian basement as a Zealandia component placed between Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton.
• KEY POINTS
• Pegasus Group, metaquartzites, Stewart Island are not correlated with the Russet Formation, Fiordland but are an Upper Devonian or lower Carboniferous sedimentary unit.
• Russet Formation high-grade metasandstones in Fiordland are correlated with the lower-grade and fossiliferous Upper Ordovician Wangapeka Formation in Nelson.
• Upper Ordovician sandstones in Western Province, New Zealand contain unusually high proportions of Neoarchean euhedral detrital zircons that suggest a local Zealandia source.
• An Archean block is proposed within the Rodinia supercontinent, between the Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton.
... No exposed Precambrian crust has been discovered to date, although isotopic evidence suggests more ancient lower crustal and sub-continental lithospheric mantle domains exist at depth (e.g. Liu et al., 2015;McCoy-West et al., 2016;McCoy-West et al., 2013;Turnbull et al., 2021). Despite these hints of ancient lithospheric roots, Zealandia's crustal history is reflective of Cambrian to Early Cretaceous growth and accretion of terranes and batholiths at the southeastern margin of Gondwana, followed by Late Cretaceous continental rifting and breakup, and Cenozoic drift and dispersal as a separate post-Gondwana continent. ...
... 129-105 Ma) Separation Point Suite on the basis of the lower Sr/Y of the granitoids (Tulloch and Kimbrough, 2003). Variations in radiogenic isotope (Sr-Nd-Hf) compositions with time are also observed through the Darran and Separation Point suites indicative of an increase in the influence of crustal sources in the migrating Mesozoic subduction arc (Milan et al., 2017;Pickett and Wasserburg, 1989;Schwartz et al., 2021;Turnbull et al., 2021). ...
... The role of deep crustal domains in the overriding Gondwana plate as controls on magma chemistry has started to be revealed by recent studies (e.g. Schwartz et al., 2021;Turnbull et al., 2021) and the Longwood Suite will be a useful end-member to incorporate in future interpretations. ...
The Cambrian to Cretaceous Tuhua Intrusives, New Zealand, preserve an igneous record of Phanerozoic subduction and crustal growth at the margin of Gondwana. Within the Tuhua Intrusives, the coeval gabbroic and trondhjemitic intrusions of the c. 261-243 Ma Longwood Suite stand out as being isotopically more primitive and chemically distinct from all other New Zealand plutonic suites. We present new U-Pb crystallization ages, trace element analyses and Sr-Nd isotope compositions of the Longwood Suite. U-Pb SHRIMP zircon ages of 258.5 ± 2.5 Ma, 256.0 ± 1.8 Ma, 247.8 ± 2.7 Ma and 243.2 ± 2.4 Ma obtained from plutons on Ruapuke Island, and a dike at Bluff, affirm the restricted time range and expand the known areal extent of the Longwood Suite. Longwood Suite granitoids are I-type and sodic (K/Na < 0.4), with distinctive low Rb and Nb/Ta, flat rare earth element patterns (La/YbN < 10), unradiogenic ⁸⁷Sr/⁸⁶Sr(t) (0.7029 to 0.7032) and radiogenic ε¹⁴³Nd(t) (+6.3 to +8.2), compared to the nearby, calc-alkaline, Late Triassic Darran Suite I-type plutons of the Tuhua Intrusives. Stable Nd isotope ratios of Longwood Suite samples are highly variable (δ146/144Nd = 233 ppm) compared to global plutonic rocks (δ146/144Nd = 44 ppm) and reflect the removal of phosphate minerals. Collectively, these geochemical characteristics are consistent with generation of the granitoids by shallow (garnet-absent) melting of an amphibolitic residue, from which we infer relatively thin lithosphere. The Longwood Suite has a maximum areal addition rate of 43 km²/Ma, substantially less than the subsequent plutonic suites when the magmatic arc was fully established. We suggest a petrotectonic model whereby Gondwana continental margin crust was tectonically underplated by Permian intra-oceanic island arc crust and mantle lithosphere, which subsequently melted to generate the isotopically primitive gabbro and trondhjemite plutons of the Longwood Suite.
... + 11 Tulloch et al. 2009) compared to the Itype lithologies which extend to more mantlelike compositions (δ 18 O = c. 5 to +10). O isotope analyses for zircons from a sample (OU49201) from the Lighthouse phase gave an average δ 18 O = +8.6 (Turnbull et al. 2021). These isotope compositions for FG are also consistent with the incorporation of a metasedimentary component such as Greenland Group (δ 18 O = 14-16 Tulloch et al. 2009) into the granitic melt. ...
The peraluminous Foulwind and Windy Point Granites are important components of the Foulwind Suite – a diverse group of high field strength element-enriched Carboniferous granitoids in New Zealand’s Western Province. Four phases are identified in the Foulwind Granite (Seal Point, Siberia Bay, Tauranga Bay, Lighthouse). A new age of 324.0 ± 4.1 Ma has been obtained for the relatively undeformed Siberia Bay phase. The rocks are generally enriched in high-field strength elements and the Tauranga Bay and Lighthouse phases can be classified as ferroan A-type granites, whereas classification of the other phases is ambiguous. Sr isotope compositions were disturbed by the formation of the Paparoa Metamorphic Core Complex. Nd isotopes vary considerably and indicate involvement of multiple sources. The Nd isotope and A-type signatures can be explained by melting of mid-Paleozoic I-type granites with variable involvement of Greenland Group metasediments. The tectonic setting of the Foulwind Suite is unclear, but may be related to processes subsequent to the generation of voluminous mid-Paleozoic granitoids and amalgamation of the Buller and Takaka Terranes.
