Joaquin Tulloch

• The University of Queensland

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, mudston...

Zircon U-Pb, and garnet Sm-Nd and Lu-Hf dates provide important constraints on local and orogenic scale processes in lower-crustal rocks. However, in high-temperature metamorphic rocks these isotopic systems typically yield significant ranges reflecting both igneous and metamorphic processes. Therefore, linking dates to specific aspects of rock his...

We present >500 zircon δ18O and Lu-Hf isotope analyses on previously dated zircons to explore the interplay between spatial and temporal magmatic signals in Zealandia Cordillera. Our data cover ~8500 km2 of middle and lower crust in the Median Batholith (Fiordland segment of Zealandia Cordillera) where Mesozoic arc magmatism along the paleo-Pacific...

We integrated new and existing bedrock and detrital zircon dates from the Zealandia Cordillera to explore the tempo of Phanerozoic arc magmatism along the paleo-Pacific margin of southeast Gondwana. We found that episodic magmatism was dominated by two high-magma-addition-rate (MAR) events spaced ~250 m.y. apart in the Devonian (370–368 Ma) and the...

We present microbeam major- and trace-element data from 14 monzodiorites collected from the Malaspina Pluton (Fiordland, New Zealand) with the goal of evaluating processes involved in the production of andesites in lower-arc crust. We focus on relict igneous assemblages consisting of plagioclase and amphibole with lesser amounts of clinopyroxene, o...

The discovery of placer tin in southern Stewart Island caused New Zealand's only known tin-rush. The source of at least some of the placer tin is greisenised granodiorite and metasedimentary rocks on the crest of the Tin Range. There are three mineralised lithologies: a sericite-quartz greisen, a quartz-topaz greisen, and a gahnite-schist greisen....

We investigated the interplay between deformation and pluton emplacement with the goal of providing insights into the role of transpression and arc magmatism in forming and modifying continental arc crust. We present 39 new laser-ablation–split-stream–inductively coupled plasma–mass spectrometry (LASS-ICP-MS) and secondary ion mass spectrometry (SI...

We report new U‐Pb zircon ages, geochemical and isotopic data for Mesozoic igneous rocks, and new seismic interpretations of mostly submerged South Zealandia (1.5 Mkm²). We use these data, along with existing geological and geophysical data sets, to refine the extent and nature of geological units. Our new 1:25 M geological map of South Zealandia p...

The new knowledge that New Zealand is part of the submerged continent Zealandia (Mortimer et al 2017), and not a South Pacific island, provides a new, continental minerals system framework for more effective exploration targeting.

Two felsic volcanic clasts from conglomerates in Fiordland and northwest Nelson provide U–Pb zircon ages of 359 and c. 362 Ma respectively; ages that occur within the interval between voluminous Western Province plutonic S-type magmatism of the Karamea and Ridge suites. Both volcanic clasts have inherited zircon populations, and trace element signa...

Major changes in tectonic style can lead to tapping of highly variable magma sources and potentially result in significant episodes of crustal growth. Here we focus on magmatism associated with a transition from arc magmatism to subsequent over-thickening and eventual orogenic collapse. This transition is associated with cessation of subduction and...

Major changes in tectonic style can lead to tapping of highly variable magma sources and potentially result in significant episodes of crustal growth. Here we focus on magmatism associated with a transition from arc magmatism to subsequent over-thickening and eventual orogenic collapse. This transition is associated with cessation of subduction and...

Sm-Nd garnet and U-Pb zircon ages for eclogite and granulite from the Breaksea Orthogneiss provide a detailed chronology for pluton emplacement and subsequent thermal history of the lower arc crust exposed in Fiordland, New Zealand. The 147Sm-143Nd ages for ~1 cm garnet grains in eclogite yield a 108.2 ± 1.8 Ma (7 points) age and similar sized grai...

The Mesozoic continental arc in Fiordland, New Zealand, records a c. 110 Myr history of episodic, subduction-related magmatism that culminated in a terminal surge of mafic to intermediate, high-Sr/Y, calc-alkalic to alkali-calcic magmas. During this brief, 10-15 Myr event, more than 90% of the Cretaceous plutonic arc root was emplaced; however, the...

The Late Devonian ultramafic–intermediate Riwaka Complex represents a rare example of magmatic-related Ni–Cu–platinum group element (PGE) sulphide mineralisation within a convergent margin setting. We provide a comprehensive review of the petrography, geochemistry, geochronology and associated Ni–Cu–PGE sulphide mineralisation for the dominant lith...

A 4.9 Mkm2 region of the southwest Pacific Ocean is made up of continental crust. The region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure. Its isolation from Australia and large area support its definition as a continent- Zealandia. Zealandia wa...

We investigate the temporal record of magmatism in the Fiordland sector of the Median Batholith (New Zealand) with the goal of evaluating models for cyclic and episodic patterns of magmatism and deformation in continental arcs. We compare 20 U-Pb zircon ages from >2300 km2 of Mesozoic lower and middle crust of the Western Fiordland Orthogneiss to e...

The 140 ± 1 Ma hypersolvus, ferroan, weakly peralkaline to weakly peraluminous North Red Head leucogranite in northwest Stewart Island is cut by quartz-pyrite-rich veins that contain a wide variety of Mo, Ag, Te, Bi, Au, Co, Cu, Pb, Zn, REE, Nb, Y, Th, U, Zr, Ti, Be and F-bearing minerals. Patchy hematite-pyrite alteration locally overprints leucog...

Carboniferous granitoids in central Stewart Island host two metalliferous hydrothermal systems that formed during emplacement of the c. 306 ± 2 Ma old Euchre Pluton and 303 ± 2 Ma Hill 267 leucogranitoid, respectively. The Ogles Creek–Silvertown Hydrothermal System (OST) on the eastern side of South West Arm, Paterson Inlet is centred on the scheel...

The Glenroy Complex consists of retrogressed monzodioritic granulites (Woodham Orthogneiss) and heterogeneous metasedimentary rocks (Davis Creek Paragneiss). U–Pb zircon dating shows that the Woodham Orthogneiss comprises rocks ranging in age from 121.8 to 126.6 Ma that are correlatives of the geochemically similar Western Fiordland Orthogneiss Wor...

New U-Pb zircon geochronology on S-, I-, and A-type granitic plutons in New Zealand refines the magmatic and tectonic history along the mid-Paleozoic Gondwana margin and provides constraints on the episodicity and dynamics of continental arc magmatism under "flare-up" conditions. High-precision isotope-dilution thermal ionization mass spectrometry...

The exhumed Fiordland sector of Zealandia offers a deep-crustal view into the life cycle of a Cordilleran-type orogen from final magmatic construction to extensional orogenic collapse. We integrate U-Pb thermochronologic data from metamorphic zircon and titanite with structural observations from > 2000 km² of central Fiordland to document the tempo...

We report new fission-track, (U–Th)/He and ⁴⁰ Ar/ ³⁹ Ar ages for minerals in surface, dredge and borehole cuttings samples from the southern South Island, Campbell Plateau and Chatham Rise regions of the Zealandia continent. Our results indicate that much of southern Zealandia underwent rapid cooling in the interval 105–80 Ma, probably during wides...

We present U–Pb zircon ages from a phosphate-cemented pebbly sandstone dredged from the central Lord Howe Rise and a 97 Ma rhyolite drilled on the southern Lord Howe Rise. Four granitoid pebbles from the sandstone give U–Pb ages in the range 216–183 Ma. Most detrital zircons in the bulk sandstone are also Late Triassic–Early Jurassic, but subordina...

Three major hydrothermal systems that contain elevated Mo, ±Ag, ±Au, ±W, Bi, ±Te are present in central and NW Stewart Island. One contains mineralized quartz veins at least 250 m long and up to 6 m thick whereas a paucity of outcrop and destruction of sulphide minerals during weathering hamper assessment of the mineralization potential of the othe...

The first comprehensive geological map, a summary of lithologies and new radiogenic isotope data (U-Pb, Rb-Sr) are presented for crystalline rocks of the Sub-Antarctic Snares Islands/Tini Heke, 150 km south of Stewart Island. The main lithology is Snares Granite (c. 109 Ma from U-Pb dating of zircon), which intrudes Broughton Granodiorite (c. 114 M...

We formally introduce 14 new high-level stratigraphic names to augment existing names and to hierarchically organise all of New Zealand’s onland and offshore Cambrian–Holocene rocks and unconsolidated deposits. The two highest-level units are Austral Superprovince (new) and Zealandia Megasequence (new). These encompass all stratigraphic units of th...

Field observations, petrography, geochemistry and U–Pb geochronology of the I-type Zetland Diorite from New Zealand's Western Province reveal a Carboniferous age of emplacement and chemical affinity with the Tobin dioritic suite. New U–Pb zircon dating by isotope-dilution thermal-ionisation mass spectrometry (ID-TIMS) provides a robust age of 347.1...

High-resolution transects across amphiboles from the layered mafic-felsic Halfmoon Pluton suggest that amphibole compositions in the outermost similar to 40 mu m of grains analyzed fluctuate in response to P-T-P-H2O conditions during the final stages of pluton emplacement and crystallization. Detailed transects (similar to 10-15 mu m point spacing)...

The cause of 7 to 25km of Early Cretaceous thickening of parts of the New Zealand Gondwana margin has been argued to be due to tectonic or magmatic processes. New insights into this event have been gained from examination of the Grebe Mylonite Zone, an extensive amphibolite facies Early Cretaceous ductile shear zone that separates volcanic arc rock...

Previous U-Pb zircon dating of the Pomona Island Granite (PIG) pluton (South Island, New Zealand) yielded either Permo-Carboniferous or Late Jurassic ages for five samples essentially indistinguishable in their field, petrographic, and geochemical characteristics. Detailed cathodoluminescence imaging and LA-ICP-MS dating of zircon in new and previo...

The ~140 Ma Halfmoon Pluton of Stewart Island, New Zealand, provides direct evidence for a number of physico-chemical processes that operate at depth within active arc settings. It is characterized by a sequence of mingled mafic sheets and enclaves that are preserved within intermediate-felsic host-rocks. Way-up structures and textures are consiste...

This paper provides a comprehensive description of the plutonic rocks of western Fiordland between Breaksea and Sutherland Sounds. The area is dominated by the Early Cretaceous Western Fiordland Orthogneiss (WFO), but also includes smaller bodies of Paleozoic and Cretaceous granitoid. Plutonic rocks of western Fiordland intrude metasediments of the...

Geothermobarometric, radiogenic isotopic and thermochronologic data are used to track the influence of an ancient continental margin (Western Province) on development of an adjacent Carboniferous-Cretaceous magmatic arc (Outboard Median Batholith) in Fiordland, New Zealand. The data show a record of complicated Mesozoic Gondwana margin growth. Para...

We report new, highly precise, U-Pb and Ar/Ar ages for seven Cretaceous rhyolites, tuffs and granites from across Zealandia spanning a 30 Ma period from arc magmatism to continental break-up. Combined with previously published data, these reveal a strong episodicity in Cretaceous silicic magmatism outside the Median Batholith. 112 Ma tuffs are know...

1] The separation of Zealandia from West Antarctica was the final stage in the Cretaceous breakup of the Gondwana Pacific margin. Continental extension resulting in formation of the Great South Basin and thinning of the Campbell Plateau leading to development of the Pacific-Antarctic spreading ridge was partially accommodated along the Sisters shea...

New U-Pb isotope-dilution-thermal ionization mass spectrometry (ID-TIMS) ages (371-305 Ma) for 30 granitic plutons along the New Zealand sector of the East Gond wanan active margin reveal a highly episodic emplacement history and crustal growth pattern. The Late Devonian-late Carboniferous ages also establish specific links with both the mostly old...

This paper provides a comprehensive description of all major plutonic rock units in Fiordland between Lakes Poteriteri and Te Anau, and the heads of Doubtful and George Sounds. Plutonic rocks comprise c. 80% of the basement in the area described, the remainder being metase dim entary and metavolcaniclastic rocks. The plutonic rocks, of which c. 50%...

Recent work by several authors has revealed that some composite plutons preserve a nearly continuous record of magma chamber processes. Detailed study of such magma chambers has the potential to identify the physical and chemical processes that govern the interaction and evolution of mafic and felsic magmas. The Bungaree Pluton on Stewart Island, N...

The character, timing, and significance of deformation within the Median Batholith has been debated since at least 1967, with allochthonous and autochthonous models proposed to account for internal variations in the character of the batholith. Stewart Island provides excellent exposures of intrabatholithic structures, allowing many aspects of the d...

This paper provides a first description of all major plutonic rock units between Resolution Island and Lake Poteriteri in southwest Fiordland. Plutonic rocks, of which c. 95% are granitoids, comprise c. 60% of the basement in southwest Fiordland. Approximately 50% of the plutonic rocks were emplaced between c. 355 and 348 Ma, 5% at c. 164 Ma, 25%be...

The Sisters shear zone is a newly discovered Late Cretaceous detachment fault system exposed for 40 km along the southeast coast of Stewart Island, southernmost New Zealand. Footwall rocks consist of variably deformed ca. 310 and 105 Ma granites that range from undeformed to protomylonite, mylonite, and ultramylonite. The hanging wall includes non-...

New mapping, structural analysis, and thermochronometry of the Sisters Shear Zone (SSZ) indicate this detachment system played a role in continental extension leading to separation of New Zealand from West Antarctica. The SSZ extends 40 km along the southeast coast of Stewart Island, southernmost New Zealand with a footwall consisting of variably d...

A peralkaline alkali‐feldspar granite dike associated with Au‐sulfide mineralisation at Sams Creek has previously yielded inconsistent Triassic K‐Ar ages, and has thwarted attempts at U‐Pb zircon dating. We report here a disturbed Ar/Ar step heating spectrum and both single and multi‐grain laser fusion analyses of amphibole, from which we interpret...

The U-Pb thermochronology of titanite, apatite, and rutile from a crustal profile through a Mesozoic magmatic arc in Fiordland, New Zealand, is used to constrain the timing and duration of significant vertical movements during arc construction and evolution. Titanite data from deep-crustal (12 13 kbar) basement and cover rocks of central Fiordland...

Exposures of basement rocks on Stewart Island provide a c. 70 km long by 50 km wide map of part of the Median Batholith that spans the margin of the Western Province. Because of their distance from the present plate boundary, these rocks are relatively unaffected by Cenozoic tectonism, allowing examination of unmodified Carboniferous‐Cretaceous rel...

The New Zealand local Clarence Series spans the Lower/Upper Cretaceous boundary and includes three stages, in ascending order, the Urutawan, Motuan, and Ngaterian. All three were defined originally from a type section at Motu Falls, Raukumara Peninsula. To address problems with their original definitions and to improve correlations between the New...

Reconstruction of detailed thermal profiles and histories in magmatic arcs is crucial for understanding arc development and evolution, because deformation, metamorphism, crustal melting, and a wide range of physical properties are temperature dependent. Fiordland, New Zealand contains a rare exposure of the deep roots of a Mesozoic magmatic arc, an...

Emplacement depths of 33 rocks from 27 Paleozoic and Mesozoic plutons from western New Zealand have been estimated utilising the hornblende‐AI barometer of Anderson and Smith. Emplacement depths for plutons from the Median Batholith/Median Tectonic Zone (Median and Separation Point Suites) plutons range from 8 to 27 km. The greatest emplacement dep...

Continental extension preceding the breakup of Gondwana in the Cretaceous produced a metamorphic core complex preserved in the Paparoa Range on South Island, New Zealand. Most features of classic Cordilleran core complexes are present including high metamorphic grade lower plate rocks separated from low-grade upper plate rocks by detachment faults,...

This paper proposes an alternative high-order, non-genetic classification of the basement rocks of medial New Zealand. More than 90% of the rocks in the Median Tectonic Zone are plutonic and can be included in part of a newly defined Carboniferous to Early Cretaceous, ca 10,200 km2 composite regional batholith - the Median Batholith. The plutonic r...

U‐Pb zircon ages of 237–180 Ma and c. 280 Ma of seven granitoid clasts from the Rainy River Conglomerate which lies within the eastern Median Tectonic Zone (Median Batholith) in Nelson, and the Barretts Formation of the Brook Street Terrane in Southland, constrain the depositional ages of both units to be no older than c. 180–200 Ma (Early Jurassic...

We present a revised interpretation of the basement geology beneath Late Cretaceous to Cenozoic Taranaki and Wanganui Basins of central New Zealand, based on new petrographic, geochemical, and geo‐chronological data from 30 oil exploration wells. Recently published structural and magnetic interpretations of the area assist in the interpolation and...

A NNE—NE trending strip, 3–8 km wide, extending from the Freshwater valley across Mt Rakeahua, Table Hill, and Mt Allen to the northern end of the Tin Range was mapped at a scale of 1:12 500 to locate and investigate the boundary between the Median Tectonic Zone (MTZ) and Western Province on Stewart Island.A NNE‐trending fault, herein termed the Es...

Broad chemical characteristics of sedimentary rocks from the Buller and Takaka Terranes have been examined, and provenance and tectonic setting inferred, using whole‐rock major and trace element data from 208 samples. Buller Terrane rocks west of the Karamea Batholith (Greenland Group) have chemistry typical of turbidite sediments deposited at a we...

The Median Tectonic Zone (MTZ) of New Zealand is a generally north trending belt of Mesozoic subduction-related I-type plutonic, volcanic, and sedimentary rocks in South Island and Stewart Island that separates Permian strata of the Eastern Province Brook Street Terrane from lower to mid-Paleozoic Gondwana margin assemblages of the Western Province...

Discordant U‐Pb zircon data from a migmatitic leucosome in amphibolite facies gneiss of the Fraser Complex define a 157 ± 21 Ma concordia lower intercept date interpreted as the age of peak metamorphism. An upper intercept date of 735 ± 100 Ma indicates inheritance of Proterozoic zircon. The mid‐Mesozoic age for high‐grade metamorphism does not sup...

In west Nelson a 130 km long belt containing granodiorite stocks with associated subeconomic stockwork Mo mineralisation is correlated with the I‐type Separation Point Suite and Western Fiordland Orthogneiss, both of Early Cretaceous age. Trace element characteristics of relatively unaltered samples of these Mo‐granite stocks, and the Separation Po...

Plutonic rocks in the Rotoroa Complex and Drumduan Terrane of South Island, New Zealand yield zircon U/Pb dates of 156 and 142 Ma, respectively, that are interpreted as crystallization ages. Hornblende and biotite 40Ar/39Ar dates of 140-130 Ma from the Rotoroa represent either emplacement ages, cooling ages or a metamorphic resetting event. These t...

Two tectonostratigraphic terranes of Palaeozoic age are recognised in the Western Province of New Zealand, separated by the north-trending Anatoki Thrust. The Buller (western) terrane is composed largely of a relatively uniform suite of quartz-rich elastics (mainly turbiditic sandstone), siltstone and black shale and ranges from basal Ordovician to...

The Sams Creek peralkaline granite is a discontinuous dike, 7 km long and up to 60 m thick, with an “outlier” a further 12 km along strike. It cuts lower Paleozoic metasedimentary rocks of the Takaka Terrane. Isotopic data suggest a Late Triassic age (226 ±1.1 Ma), which in turn suggests only minor displacement on the Devil River Thrust since this...

Basement rocks of Paleogene sedimentary basins form the present physiographic highs on the West Coast of South Island, New Zealand. Apatite and zircon fission‐track ages of these basement rocks allow interpretations to be made on the depths of Paleogene burial and the Miocene uplift history of the Victoria Range. Apparent apatite fission‐track ages...

Discordant zircon fractions from a granite sample dredged off a basement horst on the western margin of the Challenger Plateau yield a 335 ± 7 Ma lower intercept date interpreted as the crystallisation age of the granite. This age, and the modal composition of the granite, is similar to that of the Karamea Suite of Westland and Nelson, New Zealand,...

Spinel-bearing harzburgite xenoliths are described from three localities in the Western Province of New Zealand. All xenoliths have low Al2O3 contents (<0.5% wt%), orthopyroxenes are Al and Ca poor, and clinopyroxene is absent. Minor modal metasomatism evidenced by phlogopite/ amphibole veinlets is observed in a xenolith from one locality. All xeno...

Petrographic and geochemical data confirm the source of granitic detritus in the Hawks Crag Breccia of the lower Buller Gorge to be the Early Cretaceous Buckland, Blackwater, and Steele Plutons, presently disposed to the south and southwest. Detritus in the Hawks Crag Breccia in the Fox River and Bullock Creek may also be derived from the Buckland...

In Westland-Nelson provinces of New Zealand, high-grade metamorphic and granitic basement rocks showing mylonitic ductile deformation are juxtaposed beneath low-grade metasedimentary rocks and undeformed granites by uplift on low-angle detachment faults. Several metamorphic core complexes analogous to those described from western North America are...

A portable magnetic susceptibility meter allows rapid in situ estimation of the magnetite content of granitoid rocks, and hence provides a guide to their I- or S-type character.Except for some muscovite-bearing granites above about 71% SiO2 and some orthogneisses of the Charleston Metamorpbic Group, the susceptibility measurements clearly discrimin...

Granitoid rocks of Westland-—Nelson are classified into five geographically distinct batholiths and four suites. Each suite consists of rocks of similar petrographic and chemical characteristics (and probably similar age) which transgress the batholith boundaries.It is suggested that the terms Tuhua Formation and Tuhua Intrusive Group be abandoned,...