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The New Zealand Fossil Record File, an essentially complete compilation of New Zealand's known fossil record, with additional records from parts of Antarctica, SW Pacific, and elsewhere, is, to the best of our knowledge, unique. It has developed collaboratively, with contributions from university, government, industry, and avocational paleontologists and geologists. The distinctive Fossil Record Number has become an icon of New Zealand geological literature since inception of the original paper-based archive in the 1940s. Subsequently, the file has been digitised and currently holds >100,000 locality records and >1,000,000 individual taxonomic identifications spanning numerous plant and animal phyla. These numbers are continually growing. The database contains contextual information on geographic location, collection, stratigraphy and lithology of the fossil localities as well as taxonomic analyses that retain original identifications yet accommodate re-assignments. The data have been widely applied, initially for mapping, establishing age, depositional environment, etc., and more recently including in quantitative biostratigraphy, assessing completeness of the fossil record, understanding biodiversity history, extinction risk assessments, and climate analysis. In this paper, we provide a brief overview of the history of the Fossil Record File, indicate the general nature of the data it contains, and showcase a number of innovative applications of this most valuable resource. [ABSTRACT FROM AUTHOR]

Two fossil Echinoderms, a starfish (asteroid) and a brittle star (ophiuroid), are described in this paper. They were found in sandstones of Early Cretaceous age in the Te Urewera National Park, East Coast, North Island. The asteroid holotype, EC 192 Paragonaster felli n. sp., is well preserved, except that the disc lacks the integument (i.e. skin). The exposed internal structures, however, are well preserved. Five pointed arms are present, two of which are well preserved for their entire length. Varying lengths of the other three arms are obscured by matrix. The Ophiuroid, EC 194, found with the asteroid, consists of a central pentagonal disc. The mouth is edged by pairs of small triangular oral plates. Four curved arms radiate out from the disc and are distinctly demarcated from the disc. One arm is a stump. The arms are thin, smooth and almost cylindrical. No structure is visible. [ABSTRACT FROM AUTHOR]

Editorial policy and style information on the periodical "New Zealand Journal of Geology and Geophysics" is presented.

In the following paper, we apply digital mapping techniques and tephrostratigraphy to correlate marker horizons across the Whanganui Basin, culminating in a new 1:25,000 geological map of the central Rangitikei. This is achieved by (1) compilation of existing research, (2) correlation of major element glass shard datasets to known eruptive products and (3) completion of a three-year field survey. We update and refine existing stratigraphic correlations, focusing on two critical units within the basin succession; namely the Makirikiri Tuff (1.6 Ma) and Kaimatira Pumice Sand (1 Ma) formations. Okehu Group is proposed to cover all strata from Pakihikura to Potaka pumice. Rewa Pumice is placed within its own formation bridging the Makirikiri Tuff and Kaimatira Pumice Sand formations. Mapping and analysis facilitate placement of Coutts Creek Horizon within Rewa Formation. Sub-aerial surfaces and influxes of greywacke and volcaniclastic detritus from c. 1.6 Ma onward provide evidence for an alluvial plain developing at the foot of the uplifting, paleo-axial range. We suggest uplift in the paleo-axial range occurred contemporaneously with the onset of rhyolitic activity at Mangakino caldera (c. 1.6 Ma) so that the first influxes of fluvial conglomerate and volcaniclastics occur in close proximity within the eastern basin succession. [ABSTRACT FROM AUTHOR]

Numerous igneous bodies within the Deepwater Taranaki Basin are recognised mainly from seismic data and range from Early Cretaceous to Pliocene in age. They were all emplaced within an intra-plate setting but are scattered apparently at random in time and space. This paper describes the occurrences of igneous rocks within the basin as interpreted from seismic data, and discusses their possible origin. There are no indications of hotspot tracks within the Zealandia micro-continent so an alternative origin is sought. Previous authors see the main cause of volcanism as decompression melting due to localised lithospheric detachment and the movement of the Zealandia plate across the mantle as incidental. It is suggested that the movement of the Zealandia lithosphere, in the order of 4000 km to the north-northwest since the Cretaceous, may have caused drag across the asthenosphere, which in turn created transient small-scale convection cells that assisted the process of decompression melting as a modification to the accepted theory. [ABSTRACT FROM AUTHOR]

Understanding the in-situ stress field in the subsurface provides insights on the tectonic processes and seismic hazards of a basin. This paper presents observations and interpretations of present day maximum horizontal stress (SHmax) orientation from well Ranui-2 located in the onshore southern East Coast Basin. Fractures identified in the Ranui-2 image log have been divided into distinct subsets based on fracture orientation. These subsets correspond in a general sense, to changes in lithology in the well, which are associated with changes in formations. Analysis of the image log shows the present day SHmax in the borehole has two primary stress directions, W–E and NW–SE, and most of the fractures strike NE–SW. The change in SHmax occurs at a depth of circa. 1130 m measured depth (918 m true vertical depth subsea), below the depth at which the borehole changes from vertical to ≥10° deviation. When these data are compared to the regional stress field obtained using other stress indicators such as earthquake focal mechanisms, the results are consistent with each other. This study shows that shallow subsurface indications of present-day SHmax in southeastern North Island reflect SHmax orientations from deeper within the subsurface. [ABSTRACT FROM AUTHOR]

This paper synthesises geological and biological data to develop an evolutionary history for the Taieri River that currently follows a circuitous 200 km course as one of the main drainages in Otago. The ancestral Taieri River drained only coastal hills initiated in the Miocene, and much of what is now the upper Taieri catchment flowed into the ancestral Clutha River. Major river reorientation events occurred in the upper half of the catchment because of rise of antiformal fold mountains in the Pleistocene, forming a new divide between the Taieri and Clutha catchments. Coeval incision of a gorge through a volcanic rock barrier connected the upper catchment to the lower Taieri River. The sparse Pleistocene sedimentary record documents these drainage changes via contrasting distribution of distinctive clasts derived from greywacke mountains on the northern edge of the Otago Schist belt. These major capture events are also supported by distributions and genetic divergences of freshwater galaxiid fish species. Erosion during Pleistocene rise of the antiformal mountains caused recycling of placer gold into Clutha tributaries before the Taieri River evolved to its present geometry, thereby limiting the placer gold content of the modern Taieri catchment. [ABSTRACT FROM AUTHOR]

New Zealand and the southwest Pacific region have a well-preserved geological record of Late Cretaceous to Holocene volcanism. Volcanoes and volcanic fields formed in six main tectonic settings: (1) oceanic crust; (2) large igneous provinces; (3) subduction-related volcanic chains; (4) intraplate related to Late Cretaceous rifting of Zealandia from Gondwana; (5) intraplate in Cenozoic age progressive chains that define so-called hotspot tracks; and (6) intraplate with a scattered, Cenozoic, non-age progressive, non-rift-related distribution. At least 500 volcanic fields, stratovolcanoes and seamounts, active within the last 105 million years, can be identified within the c. 5 million km2 area of Zealandia continental crust. Volcanic rocks from onland New Zealand are the best-studied and dated but represent material from less than a fifth of Zealandia's volcanoes and volcanic fields. [ABSTRACT FROM AUTHOR]

New Zealand has a network of approximately 190 Continuously Operating Reference Stations (CORS) operated by GeoNet, is a project housed within GNS Science. The GeoNet continuous GNSS network (cGNSS) includes the 37 stations that make up the Land Information New Zealand (LINZ) PositioNZ network. These stations are run in partnership by the two agencies. The New Zealand CORS stations make a significant contribution to New Zealand's geospatial infrastructure and to international geodesy. Further, the CORS stations have been used to identify more than 25 slow-slip events (SSEs) associated with the Hikurangi subduction zone, play an important role in volcano monitoring and have the potential to identify tsunamigenic earthquakes. This paper will discuss how the two networks were established, how they have evolved since the first stations were established in 1995 and the significant contribution of the late John Beavan. [ABSTRACT FROM PUBLISHER]

The article offers information on the "New Zealand Journal of Geology and Geophysics."

Fragile holoplanktonic gastropods are rare components of the rich and diverse New Zealand Cenozoic molluscan fauna. This paper describes a new species in the extinct genus Gamopleura, G. maxwelli n. sp., from the Late Oligocene Otekaike Limestone, South Canterbury. Its only known congeners are found in Late Oligocene/Early Miocene rocks in southern Europe. [ABSTRACT FROM AUTHOR]

Treatment of acid mine drainage can be accomplished by either active or passive treatment systems. Choice between active and passive treatment and appropriate selection of systems within each category is critical for treatment success. In general, active treatment is more commonly used at operational mines whereas passive treatment is typically considered for closed and abandoned mines. Operational mines often have limited space for remediation systems and have large and fluctuating flow rates with changing drainage chemistry as mining proceeds, factors that are addressed more easily with active than passive treatment. In the long term, passive treatment could offer more economic options than active treatment. Various flow charts have been prepared by previous researchers to help select among the passive systems but little work has been done to help select between active and passive treatment or to select appropriate active treatment systems. Furthermore, the passive treatment flow charts have often not included variables important for application to New Zealand sites: topography, climate and available land area. Very steep topography, dense and often protected vegetation, and a high-rainfall climate may result in acid mine drainage with high flow rates in locations with limited space for remediation. This paper presents flow charts specific to New Zealand which have been prepared to accommodate topography and available land area. [ABSTRACT FROM AUTHOR]

An important component of quantifying seismic hazard and risk in regions such as Wellington is to characterise both the long-term rate of occurrence of the region's major earthquake-generating active faults, as well as potential interactions between faults (e.g., the potential for earthquake triggering). This paper describes paleoseismic data from two trenches (Ohariu Valley) and a natural streambank exposure (Horokiri valley) c. 24 km apart, which constrain the timing and size of recent surface rupture events on the northeast striking Ohariu Fault c. 6 km northwest of Wellington City. One event is recorded at all three sites and radiocarbon age constraints indicate it correlates with the 1050-1000 cal. years BP event previously identified elsewhere along the fault. A younger, smaller (decimetre-scale) event is recorded in one of the Ohariu Valley trenches, and the timing is constrained by two radiocarbon ages to post-310 cal. years BP. This event may either be a small, primary Ohariu Fault rupture, or a triggered event associated with a large earthquake on a nearby fault. If it is a triggered rupture, then a possible mechanism is dynamic triggering associated with one of the recent large-great earthquakes on the Wellington (post-300 yr), Wairarapa (AD1855), or Awatere (AD1848) Faults. Small rupture events do not necessarily contribute to the recurrence interval classification of the Ministry for the Environment Active Fault Guidelines, but they could be important for sensitive structures crossing the fault and for lifelines crossing multiple active faults. [ABSTRACT FROM AUTHOR]

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 Western Province, many of whose age and terrane affinities remain undefined. Paleozoic granitoids in western Fiordland include the Pandora Orthogneiss (c. 500 Ma) and widespread related sills within Paleozoic metasedimentary rocks; the All Round Pluton (c. 340 Ma); the Deas Cove Granite (c. 372 Ma); and possibly the Straight River Granite. The Pandora Orthogneiss is one of the oldest plutons yet found in the Median Batholith. Correlatives include the Jaquiery Granite Gneiss in central Fiordland and orthogneiss in Doubtful Sound. Plutonism of Ross/Delamarian age is therefore widespread in those parts of Fiordland where cambrian or older Western Province metasedimentary rocks form basement. The All Round Pluton and Deas Cove Granite are correlatives of the S-type Ridge and A/I-type Foulwind Suites, respectively. The c. 125-116 Ma WFO includes at least seven major dioritic and monzodioritic plutons in western Fiordland, one in central Fiordland, and one in central Stewart island. Plutons which compose the WFO are distinguished by differences in their age, petrography, structural and metamorphic histories, and geochemistry. The WFO in northern Fiordland and the correlative Walkers Pluton on Stewart island were emplaced in the mid crust (4-9 kbar) at depths comparable with some Separation Point Suite plutons of similar age. WFO plutons in southern Fiordland were emplaced at greater depths (10-18 kbar). WFO plutons have been variably recrystallised to eclogite; omphacite-, garnet-, two-pyroxene-, and hornblende-granulite; and hornblende-amphibolite facies assemblages, reflecting different PTX conditions during metamorphism of each body. Some parts of the WFO remain undeformed and unmetamorphosed. evidence of up to c. 6 kbar loading after emplacement is limited to WFO plutons in northern Fiordland and adjacent country rocks. extensional ductile shear zones previously shown to locally separate the WFO from adjacent rocks are discontinuous later features, commonly localised along earlier intrusive contacts between WFO plutons and metasedimentary country rocks. They do not form a regionally extensive detachment between the upper and lower plates of a metamorphic core complex. The WFO has previously been included in the Separation Point Suite since both units share a high Sr/Y (HiSY) chemistry and were emplaced at broadly the same time. However, the WFO and Separation Point Suite have distinct chemistries. Separation Point Suite rocks generally contain greater Sr, Na, and Al, and have lower Sr/Rb ratios, rare earth element and Y contents, than WFO rocks with comparable amounts of SiO2. Many aspects of the WFO chemistry (aside from its HiSY character) are similar to that of the older Darran Suite rather than the Separation Point Suite. This may reflect a greater amount of partial melting during generation of the SiO2-poor WFO than the SiO2-rich Separation Point Suite. Alternatively it may indicate derivation of the WFO and Separation Point Suite from different sources, albeit at depths greater than those where residual plagioclase is stable. Relatively large variations in the major element chemistry of the Separation Point Suite reflect fractionation and/or accumulation of plagioclase, whereas the more limited variability in the major element chemistry of the WFO reflects minor fractionation and/or accumulation of hornblende and/or clinopyroxene. [ABSTRACT FROM AUTHOR]

The Repongaere Fault is one of a series of active normal faults within the Raukumara Peninsula, eastern North island, New Zealand. These faults appear to form in response to rapid uplift of the Raukumara Range and related extensional strain. however, the activity of these normal faults is poorly constrained. This paper presents new mapping of the active surface trace of the Repongaere Fault, c. 18 km northwest of Gisborne, and the results of two paleoseismic trenches. These results are then used to assess the seismic hazard posed by this fault and impacts on the Waipaoa Sedimentary System in which the fault is situated. active traces can be mapped for c. 4.5 km, but we infer the surface rupture length to be at least 9 km. Tephras within the trenches constrain the timing of the most recent surface rupture event to have occurred during deposition of the Waimihia Tephra (c. 3400 cal. yr BP), and at least one event in the period c. 13 800-5470 cal. yr BP, with single-event displacements of ≥ 0.4-1.1 m. From these data a mean dip-slip rate of c. 0.1 mm/yr and a maximum recurrence interval of 4490-6900 yr, can be calculated. if the Repongaere Fault is representative of other Raukumara Peninsula normal faults, then this relatively low rate of activity supports the interpretation that these faults are not contributing significantly to the deformation of the Raukumara Peninsula. The low rate of activity is also consistent with the very localised evidence for landscape impacts, a calculated moderate Mw of 6.3-6.7, and the fault's location within the lower part of the Waipaoa River catchment. Together, these observations suggest that Repongaere Fault earthquakes have minimal, localised impact on the Waipaoa Sedimentary System. [ABSTRACT FROM AUTHOR]

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 metasedimentary and metavolcaniclastic rocks. The plutonic rocks, of which c. 50% are granitoids, were emplaced in three phases--at c. 492 Ma, between c. 365 and 318 Ma, and between 168 and 116 Ma. correlatives of the Devonian Karamea Suite emplaced between c. 375 and 367 Ma, and the Triassic to Early Jurassic part of the Darran Suite emplaced between c. 230 and 168 Ma, are not present in the area described here. The strongly deformed Late Cambrian to Early Oordovician Jaquiery Granitoid Gneiss is one of the oldest plutonic rocks yet discovered in New Zealand and is of similar age to plutonic rocks within the Ross and Delamerian Orogens of Victoria Land and South Australia. Rocks emplaced between c. 365 and 318 Ma include Ridge Suite S-type granitoids and closely related S/A-type plutons, Foulwind Suite A-type mafic and granitoid plutons, Tobin Suite I-type granitoids, and several unassigned mafic plutons. Rocks emplaced between 168 and 116 Ma include extensive c. 168-128 Ma old calc-alkaline loSY gabbros, diorites, and granitoids of the Darran Suite, c. 165-135 Ma old hypersolvus perthitic syenogranites and peralkaline granitoids, c. 125 Ma gneissic diorite similar to the Western Fiordland Orthogneiss, and c. 123-116 Ma old quartz diorites and granitoids of the HiSY Separation Point Suite. Plutons from each suite tend to be concentrated in distinct NNE-striking parallel belts up to 20 km wide and 110+ km long. These belts are one of the key features which define the regional structural grain of Fiordland basement geology. Their strike remains constant from the Carboniferous through to the Cretaceous. S, S/A, and A-type plutons of the Carboniferous Ridge and Foulwind Suites are confined to a 125 km long but discontinuous belt in southern and central Fiordland, wholly within the areal extent of early Paleozoic metasedimentary basement. Volumetrically minor Carboniferous Tobin Suite I-type granitoids are confined to the area east of exposed early Paleozoic metasedimentary basement. Much of eastern Fiordland is underlain by an extensive belt of heterogeneous Darran Suite rocks. Darran Suite rocks extend from Stewart Island to the Darran Mountains of northern Fiordland, forming a belt c. 15 km wide and 300 km long. Correlative Darran Suite rocks also occur further west where they intrude early Paleozoic metasediments, indicating that Jurassic to Early Cretaceous arc-related plutonism and volcanism occurred inboard of the edge of early Paleozoic basement in some parts of the Median Batholith. distinctive Jurassic, pink, hypersolvus syenogranite and alkalic granitoids form a narrow discontinuous belt within the wider calcalkaline Darran Suite. Cretaceous Separation Point Suite plutons form two major belts, one in easternmost Fiordland partially covered by Cenozoic sedimentary rocks, and the other stitching inboard and outboard parts of the Median Batholith in central Fiordland. [ABSTRACT FROM AUTHOR]

The late Cretaceous Rakopi Formation (Pakawau Group) represents one of the most important petroleum source rock units and a potential reservoir unit in the highly prospective Taranaki Basin. This paper presents a predominantly outcrop-based study of the sedimentology, petrography, stratigraphy, and depositional environment of the Rakopi Formation in the Paturau River and Pakawau areas of northwest Nelson, southern Taranaki Basin, together with some preliminary insights into the stratigraphic architecture of the Pakawau Group on a more basin-wide scale. The Rakopi Formation is interpreted here as a terrestrial deposit, representing sedimentation in fluvial channels and their associated overbank and levee environments. However, the presence of dinoflagellates, glauconite, and elevated coal seam sulfur contents is evidence for periodic marine influence during deposition. This could be explained by a low-gradient coastal plain paleogeography, crossed by a series of rivers and their associated floodplain deposits, episodically inundated by marine incursions during successive transgressions. A modern analogue setting from the present-day Hauraki Graben, North island, New Zealand, indicates that marine influence within coastal plain systems can extend several tens of kilometres inland. Given such a physiography, relatively small increases in relative sea level could potentially move the shoreline several kilometres or tens of kilometres farther inland, sufficient to introduce the type of marine influence on sedimentation that we suggest for the Rakopi Formation. The results from this study suggest a greater marine influence within the Rakopi Formation, northward into the greater Taranaki Basin, than has previously been recognised. This raises the possibility of both different reservoir facies as well as potentially a greater proportion of marine mudstones, which would have implications for both reservoir and trapping of hydrocarbons. In addition, marine-influenced coaly rocks within the Rakopi Formation are expected to have greater petroleum generative potentials and to be more oil-prone than their fully non-marine counterparts. [ABSTRACT FROM AUTHOR]

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% between c. 140 and 125 Ma, and 20% between c. 125 and 110 Ma. These episodes of plutonism occurred in response to terrane amalgamation, continental thickening, and subduction along the convergent margin of Gondwana. Correlatives of Devonian plutonic rocks which occur in Nelson are absent from the area described here. A wide variety of plutonic rocks were emplaced at c. 355- 348 Ma. These include relatively small plutons of K- and Rb-rich gabbro-diorite and members of at least three distinct suites of granitoids. Plutons of two-mica ± garnet granodiorite, granite, and minor tonalite share affinities with the S-type Ridge Suite and are the most widespread c. 355-348 Ma old granitoids in southern Fiordland. Plutons rich in Ca, Fe and Zr, depleted in K and Na, and containing quartz diorite, tonalite, and minor granodiorite with the unusual assemblage red-brown biotite, garnet ± hornblende ± clinopyroxene also occur widely in southern Fiordland. These plutons are similar to peraluminous A-type granitoids, indicating A as well as I and S-type plutonism occurred in the Western Province at this time. The Newton River and Mt Evans Plutons have no correlatives amongst c. 355-348 Ma granitoids in southern Fiordland, but their chemistry is similar to that of the older Karamea Suite. Three regional-scale metasedimentary units--locally fossiliferous Fanny Bay Group Buller Terrane rocks in southern Fiordland, Edgecumbe and Cameron Group Takaka Terrane rocks in south-central Fiordland, and undifferentiated Deep Cove Gneiss high-grade metasedimentary rocks of western Fiordland--are all stitched by c. 355-348 Ma old plutons, indicating they have been in close proximity since at least c. 355-348 Ma. in south-central Fiordland, c. 355-348 Ma old plutons cut across fabrics defined by upper amphibolite facies mineral assemblages, indicating low pressure/high temperature metamorphism in this area before this time. The c. 164 Ma old leucocratic Lake Mike Granite is a unique pluton in southwest Fiordland with no obvious correlatives. Plutons emplaced between c. 140 and 125 Ma are similar to the Rahu Suite, although isotopic data are required to confirm this correlation. Rahu Suite plutonism may therefore have begun by c. 140 Ma, rather than c. 120 Ma as previously suggested. Plutons emplaced between c. 125 and 110 Ma have high Sr/Y ratios comparable with the Separation Point Suite. They occur in both an outboard location around lake Poteriteri and an inboard location around the western end of Dusky Sound. The c. 115 Ma two-mica garnet granites of the Anchor Island Intrusives #2 probably formed by partial melting of adjacent ortho- and paragneisses, indicating that upper amphibolite facies metamorphism in western Dusky Sound occurred during the early Cretaceous. The Dusky Fault does not pass directly out to the coast through outer Dusky Sound as previously mapped. Instead it merges with the major northeast-striking lake Fraser Fault at Cascade Cove, which crosses the outer coast near West Cape. The last Cove Fault is a minor structure which cannot be traced beyond last Cove rather than a major fault of regional extent as has been previously suggested. [ABSTRACT FROM AUTHOR]

We develop procedures for evaluating the efficacy of the M8 algorithm and producing probability forecasts in both time and space. Our modelling method uses the Critical Series developed by Harte et al. in 2003 as a predictor variable in a logistic regression. The M8 algorithm calculates seven time series, and the Critical Series embodies the nonlinear rules for combining the behaviour of these seven time series. The M8 algorithm is typically evaluated in (spatial) circles of quite large radius. Our implementation of this has many large overlapping circles covering New Zealand. This raises both practical and statistical problems. From a practical perspective, we really want probability forecasts within relatively small non-overlapping synoptic cells. Further, statistical evaluation of the overlapping circles approach is complicated by the lack of independence. In this paper, we develop both the overlapping circle and synoptic forecasting methods and statistical tests for their evaluation. We then compare results of the two approaches. Although the results indicate a significant relationship between the M8 Critical Series and numbers of large earthquake events, the forecasting success may be largely due to their dependence on slow variations in deep activity, which might be better examined directly as a possible source of predictive information. [ABSTRACT FROM AUTHOR]

This paper presents a systematic review and correlation of river terraces identified in 44 river catchments in the North Island, New Zealand, to assess river behaviour over the last c. 30 000 yr. This provides a comprehensive foundation from which to assess controls on river dynamics over this critical period of landscape development from the last glacial through to the present interglacial. From this review, an integrated framework for elucidating fluvial responses to environmental change is proposed. Sensitivity of river systems to climate change is variable over this time-scale. Substantial sediment inputs to valley floors during the last glacial reduced sensitivity to subtle climatic shifts. Sensitivity increased during the Holocene, with terraces forming in response to episodes of storminess. Tectonics and volcanic activity may both override climatic forcing to cause either cutting or filling of the valley floor. [ABSTRACT FROM AUTHOR]

An introduction to the periodical is presented in which the editor discussed various topics within the issue including New Zealand national velocity field, the relationships between seismicity and slow-slip events (SSEs) in the Hikurangi margin and Hikurangi subduction margin.

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 the country's Cambrian–Early Cretaceous basement rocks and Late Cretaceous–Holocene cover rocks and sediments, respectively. Most high-level constituents of the Austral Superprovince are in current and common usage: Eastern and Western Provinces consist of 12 tectonostratigraphic terranes, 10 igneous suites, 5 batholiths and Haast Schist. Ferrar, Tarpaulin and Jaquiery suites (new) have been added to existing plutonic suites to describe all known compositional variation in the Tuhua Intrusives. Zealandia Megasequence consists of five predominantly sedimentary, partly unconformity-bounded units and one igneous unit. Momotu and Haerenga supergroups (new) comprise lowermost rift to passive margin (terrestrial to marine transgressive) rock units. Waka Supergroup (new) includes rocks related to maximum marine flooding linked to passive margin culmination in the east and onset of new tectonic subsidence in the west. Māui and Pākihi supergroups (new) comprise marine to terrestrial regressive rock and sediment units deposited during Neogene plate convergence. Rūaumoko Volcanic Region (new) is introduced to include all igneous rocks of the Zealandia Megasequence and contains the geochemically differentiated Whakaari, Horomaka and Te Raupua supersuites (new). Our new scheme, Litho2014, provides a complete, high-level stratigraphic classification for the continental crust of the New Zealand region. [ABSTRACT FROM AUTHOR]

The author discusses the 150th anniversary of the New Zealand Geological Survey, which became the country's first national scientific institution

Sand volcanoes produced by liquefaction of saturated sands were widespread in the Avon–Heathcote Estuary following individual major events of the Christchurch 2010–2011 Earthquake sequence. Sand volcanoes were composed of fine grey sands and varied in diameter over the range 0.2–5 m, fed by vertical to subvertical feeder pipes of 15–25 cm diameter that cross-cut mud and shell horizons. Tides and wind-driven waves reduced, and at times removed, the profile of surface features; however, subsurface features remained unaffected. The geological signature of these volcanoes, formed in wet sandy tidally influenced settings such as estuaries, would be preservation of straight-sided feeder pipes 15–25 cm in diameter, >30 cm in length that cross-cut undeformed strata with or without expression of the erupted cone. Sediments were not able to be excavated beneath the shallow water table, and all observed feeder conduits occurred as roughly cylindrical pipes rather than elongated planar dykes; this does not preclude dykes being present deeper in the subsurface, however. Coseismic subsidence may enhance the preservation potential of surface features by increasing relative water depth, thereby increasing sedimentary accommodation space, and decreasing the influence of wave action in removing cones. [ABSTRACT FROM PUBLISHER]

Cretaceous gastropod molluscs are recorded from Chatham Island for the first time, represented by rare silicified species from the Takatika Grit, which has been dated from mollusc, vertebrate, and dinoflagellate evidence as Campanian (Late Cretaceous) in age. Species identified comprise Protodolium sp. cf. P. pittensis Stilwell, 1994 (Neritopsidae); Euspira selwyniana (Wilckens, 1922) (Naticidae); and Eriptychapunamutica Wilckens, 1922 (Ringiculidae), all shallow-water shelftaxa. Coeval, conspecific taxa are known from the Kahuitara Tuff from Pitt Island, and from the New Zealand mainland, in comparable shallow shelf habitats. [ABSTRACT FROM AUTHOR]

Roasted residues from historic gold mine processing at the Golden Point historic reserve were thoroughly cemented by surfical processes. The cements are composed mainly of oxidised and acidic Fe–As–S minerals with varying particle size and crystallinity. Bukovskyite (Fe2[AsO4][SO4][OH].7H2O) and scorodite (FeAsO4.2H2O) are the most prominent of these minerals, but a range of As and S bearing ferric iron oxyhydroxide compounds are also abundant, including K-jarosite and schwertmannite. Arsenolite (As2O3) is a minor component, either persisting from original roasting or precipitated via local reduction in the cement. After the historic roasting the residues were treated with liquid Hg to extract gold, and some of that Hg remains in the residues. This Hg now occurs as microcrystalline schuetteite (Hg3[SO4]O2), remobilised nano-scale liquid Hg droplets, and as micron-scale Hg-rich layers in ferric iron oxyhydroxide compounds in the cements. Tungsten mobilised from primary ore scheelite is contained in ferric iron oxyhydroxide and as Fe-meymacite (WO3.xFe2O3.nH2O) in the cements. The cementation processes have effectively confined metals within the residues. [ABSTRACT FROM AUTHOR]

The Snowy River processing site was used to extract gold for the large historic Blackwater mine, Westland, between 1906 and 1938, and then abandoned. The site is now one of the best-preserved historic gold-processing localities, and access has been enhanced for visitors. The site has some high arsenic (As) concentrations on the surface, with some spots exceeding 40 wt% As. A variety of As-bearing minerals occurs along the former processing stream, from primary sulphides (arsenopyrite, pyrite) at the upstream end to arsenolite (As2O3) and scorodite (FeAsO4.2H2O) formed by the roasting of ore materials at the downstream end. Weathering over the past century of sulphide residues and some of the arsenolite has yielded more scorodite and some Ca arsenates. Minor authigenic As sulphide precipitates have formed on rotting wood. Arsenolite is principally distributed near to the roaster site, and this is the most soluble and potentially toxic mineral on site. Despite the locally abundant arsenolite, only minor As is mobilised into nearby waters. [ABSTRACT FROM AUTHOR]

Coasts in tectonically active regions face varying threat levels as land subsides or uplifts relative to rising sea levels. We review the processes influencing relative sea-level change in New Zealand, and the geological context behind ongoing land movements, focussing on major population centres. Whilst Holocene sea levels have been reconstructed using a variety of techniques, recent work uses salt-marsh microfossil assemblages to reconstruct relative sea-level changes over the past few centuries. For the twentieth century, these proxy-based studies often show enhanced rates of sea-level rise relative to tide-gauge observations. The effects of tectonic subsidence must be considered, alongside vertical and dating uncertainties in the sea-level reconstructions. Global Positioning Systems (GPS) observations for the past few decades show that vertical land movement (VLM) may be influencing rates of relative sea-level rise. However, the short period of GPS observations, during which trends and rates have varied at some localities, raises questions over the longer-term contribution of VLM to sea-level change over the past few centuries and for future projections. We argue that high-resolution palaeo-sea-level reconstructions from salt-marsh sedimentary sequences can help to answer these questions regarding the interplay between sea-level change and VLM at key locations. [ABSTRACT FROM AUTHOR]

Cenozoic geological evolution of New Zealand centres around the formation of Zealandia, a new continent that became detached from the eastern margin of Gondwana around 105 Ma. Spreading opened the Tasman Sea leaving a fragment of continental lithosphere, largely submerged, in the SW Pacific. Throughout the Cenozoic history, volcanism became an integral part of Zealandia. Continental lithosphere provided the basement for the volcanism, both onshore and offshore. Monogenetic volcanism was common throughout the Cenozoic. The availability of water was ubiquitous through surface water bodies (oceans and lakes) and various other terrestrial hydrous systems provided by the humid temperate climate of Zealandia. Hydrovolcanism, both explosive and non-explosive, has played a significant role in Zealandia's volcanic history resulting in volcano mega- architecture involving edifice geology and volcanic hazards. However, hydrovolcanism has commonly been overlooked in Zealandia's monogenetic volcanism context. Cenozoic monogenetic fields of Zealandia provide a unique laboratory and comparative analogy for other volcanic fields on Earth that are associated with low-lying terrestrial settings or shallow marine environments in a humid temperate climate. [ABSTRACT FROM AUTHOR]

Sr-Nd-Hf-Pb isotopes and major/trace element data are presented for amphibole megacrysts from two separate instances of lamprophyric intraplate magmatism in Zealandia (Cretaceous Westland Dike Swarm and Cenozoic Alpine Dike Swarm). Megacrysts from both regions have comparable geochemical and isotopic signatures (87Sr/86Sr(i) = 0.702754–0.703371, εNd(i) = +3.9 to +5.5, εHf(i) = +5.0 to +8.2, 206Pb/204Pb(i) = 18.909–20.526, 207Pb/204Pb(i) = 15.642–15.678, 208Pb/204Pb(i) = 38.824–40.271), regardless of them having traversed contrasting crustal terranes at different times and tectonic settings. Several megacryst cores may represent early-crystallised phenocrysts, whereas rims crystallised in equilibrium with amphibole microphenocrysts during final emplacement of host melts. Strontium isotopic offsets between megacrysts and host rocks indicate secondary hydrothermal alteration in some lamprophyres. Correlations between host rock – megacryst geochemistry as well as evidence for amphibole fractionation in Zealandia lamprophyres indicate that megacrysts likely crystallised from melts similar to their hosts. Isotopic (Pb, Nd) and Mg# offsets suggest a non-cognate relationship and reflect interaction between isotopically heterogeneous lamprophyric melts and/or cumulate amphibole in the lower crust. Modelling suggests that most alkaline intraplate magmatism throughout Zealandia may be derived from moderately heterogeneous SCLM sources that experienced localised varying degrees of subduction-related carbonatitic metasomatism between the Jurassic to Middle Cretaceous during Gondwana break-up. [ABSTRACT FROM AUTHOR]

New Zealand has a remarkably large number of exhumed mantle occurrences for a small exposed landmass. Since the last regional syntheses of peridotite (1987) and serpentinite (1966) , new locations have been discovered and abundant geochemical and isotopic data have been acquired. Mantle peridotite is known from nine massifs along the base of the Dun Mountain Ophiolite Belt (DMOB), xenoliths in volcanic fields in at least 75 localities, and as one 15 km-long orogenic body in Fiordland. In these occurrences, spinel peridotite is abundant, plagioclase peridotite is restricted to the DMOB, and garnet peridotite is absent. The xenoliths and orogenic peridotites represent exhumed lower portions of Phanerozoic continental lithosphere, whereas the ophiolites represent accreted oceanic lithosphere. Hydrated peridotite (serpentinite) is even more widespread, and extensively developed in three ophiolites (Dun Mountain, Northland and Pounamu). Serpentinite is also associated with some altered igneous ultramafic and mafic rocks. The recently acquired data have led to discoveries including the occurrence of Archean and Proterozoic mantle lithosphere under Zealandia, the presence of regional-scale fertile and refractory mantle lithosphere domains, isotopic similarities between metasomatised mantle and intraplate volcanic magmas, and characterisation of serpentinite during faulting. [ABSTRACT FROM AUTHOR]

Volcaniclastic and coherent volcanic rocks of the Permian island arc Brook Street Terrane crop out along the Southland coast, New Zealand, near Riverton. Extensive along-strike exposures reveal lateral variations in these submarine deposits and provide a rare opportunity to examine deposits of an arc environment within a thin slice of time. We describe pillow lavas, dikes, hydroclastic breccias, tuffs, lapilli tuffs and argillites, all hydrothermally altered and metamorphosed to prehnite-pumpellyite facies. Trace element geochemical data indicate multiple primitive island arc to MORB-like magma sources. Two separate volcanic centres apparently tapped different mantle domains in a source region transitional between the arc and back-arc. The centres' proximity and inferred small sizes suggest they were satellite vents of a larger arc volcano. Tuff and lapilli tuff were formed as hyaloclastite during eruption of pillow lava, and redeposited by subaqueous mass flows. Peperitic contacts indicate that the lavas intruded unconsolidated volcaniclastic deposits. We infer that hydroclastic fragmentation associated with pillow emplacement produced debris that was then intruded by later pillows, with local peperite formation, as eruption persisted. The hydroclastic debris from these satellite vents was resedimented in turbidite fans with channels, and periodic turbidity currents delivered fine-grained material from the volcano's main vent. [ABSTRACT FROM AUTHOR]

The Alpine Dyke Swarm (ADS), intruding Haast Schist in the Southern Alps, New Zealand, comprises dykes, sills and diatremes of alkaline and ultramafic lamprophyres, phonolites and carbonatites. Intrusion peaked at ∼25 Ma during inception of dextral transtensional displacement on the Alpine Fault plate boundary. In a chamber beneath Haast River, magmas evolved by fractional crystallisation from primitive lamprophyres to phonolites, and then by liquid immiscibility to carbonatite magmas. Carbonatitic magmas coexisted with a highly sodic fluid that metasomatised adjacent quartzofeldspathic schist to aegirine-albite fenites. Carbonatites fractionated from Ca- to Fe-rich and, under late-stage, hydrothermal conditions, to Ba-Sr-REE–rich varieties. Some lamprophyres rose directly from a highly refractory spinel- or possibly garnet-spinel peridotite mantle that had been extensively metasomatised prior to the low-degree partial melting event and Cr-diopside series nodule entrainment. Al-augite series nodules give ages similar to host lamprophyres and are interpreted as deep-seated cognate cumulates. Compared to the broadly coeval basaltic-basanitic magmas of the Dunedin Volcanic Group (DVG) of East Otago, ADS magmas are enriched in volatiles, LILE, and HFSE (including REE). DVG magmas were derived from a less metasomatised mantle source, and, although undergoing extensive fractionation, failed to achieve the extreme alkali enrichment necessary for silicate melt-carbonatite immiscibility. [ABSTRACT FROM AUTHOR]

The Reefton goldfield includes the large Globe Progress and Blackwater deposits as well as ∼30 smaller deposits which are localised along a network of late syn- to post-metamorphic faults and shear zones that extend 25+ km in a northerly direction. The Globe Progress deposit is located in a unique structural site where this district-scale zone of mineralised faults and shear zones splits into two strands. Lense-shaped zones of mineralised quartz veins <100 m long which form the smaller deposits plunge parallel to intersections between their host faults and the S2 cleavage or bedding. Veining likely developed in minor dilational jogs where the faults refract across cleavage or bedding. Some dilational jogs formed during dextral strike-slip and transpressional-reverse movement along the host faults in response to a NE-SW oriented σ1. Faults that host the smaller deposits are located on east-dipping fold limbs, whereas the larger, tabular rather than rod-shaped, Birthday Reef at Blackwater is the only deposit and associated fault located on a WNW-dipping fold limb. This unusual structural setting was presumably more conducive to dilational opening in the prevailing stress field. None of the deposits within the goldfield are located in major fold hinges. [ABSTRACT FROM AUTHOR]

Fossil penguins from late Neogene sediments are important for understanding the origins of modern penguins. Recent advances in penguin taxonomy and geometric morphometrics allow us to revisit previously described Pliocene fossils and potentially gain new insight into the evolutionary relationships of early crown penguin species. Here we re-evaluate the holotype of Tereingaornis moisleyi, a Pliocene fossil penguin discovered near Te Reinga Falls in the North Island of New Zealand. The holotype (hereafter referred to as the Te Reinga Falls fossil) does not possess any apomorphies that justify recognition as a distinct genus or species, and cannot be distinguished from the living crested penguins (Eudyptes spp.) or yellow-eyed penguin (Megadyptes antipodes) using discrete osteological characters or morphometric analysis. We propose that Tereingaornis moisleyi be considered a nomen dubium. The Te Reinga Falls fossil indicates that a penguin approximately the size of the extant tawaki (Fiordland crested penguin, Eudyptes pachyrhynchus) was present in New Zealand during the middle of the Pliocene (Waipipian Stage, 3.7–3.0 Ma), but a more complete specimen would be needed to confidently resolve the evolutionary relationships between this fossil and other penguins. [ABSTRACT FROM AUTHOR]

Epidosites occur in association with pelagic and quartzofeldspathic metasediments overlying the Pounamu suprasubduction zone ophiolite. They are dominated by epidote with minor diopside, tremolite, titanite, zircon and quartz. Detrital zircon age spectra are similar to those of associated quartzofeldspathic schist, with minimum ages of Cretaceous (c. 106 Ma). Epidosite was derived by metasomatic replacement of this metasedimentary protolith by Ca-rich fluids, likely derived from the underlying ophiolite. One epidosite contains laminae and veinlets of molybdenite, which yields a Re/Os age of c. 89.7 ± 0.6 Ma. Metasomatic formation of epidosite and molybdenite mineralisation occurred during the interval between c. 106 and c. 70 Ma when the Pounamu terrane component of the Alpine Schist underwent accretion, subduction, hydrothermal alteration, mineralisation and metamorphic recrystallization. Molybdenite occurrence is unique in the context of Haast Schist metallogenesis, with Mo most likely derived by leaching and redistribution from the sedimentary cover of the Pounamu ophiolite. [ABSTRACT FROM AUTHOR]

The Waimea-Flaxmore Fault System (W-FFS) comprises NE-striking, SE-dipping reverse faults superposing Eastern Province terranes on Cenozoic sedimentary units of the Moutere Depression. We present a revised geological map and cross sections of the W-FFS in the Nelson-Richmond urban area, aimed at reconstructing the structural evolution during multiple phases of reactivation. Our data and structural interpretations depict the inversion of the W-FFS from an inherited system of Late Cretaceous-Eocene normal faults to multiple reverse fault splays that propagated through the cover sequence over the last 10 Ma. Fault tip propagation with folding of the cover sequence persisted during the Quaternary, with breaching of the Waimea and Flaxmore faults to the surface and propagation of a splay thrust (Tahunanui Fault) still concealed beneath Quaternary deposits. Ongoing crustal shortening associated with the Pacific-Australian plate boundary in the northern South Island creates favourable conditions for reactivation of the long-lived W-FFS in the contemporary stress field. [ABSTRACT FROM AUTHOR]

Thirty-eight non-tropical carbonate rock samples with subtropical affinities, from northern Zealandia, were obtained from oceanographic dredging expeditions in the Reinga-Aotea Basin (2013), and the Norfolk, Loyalty, and Three Kings ridges (2015). Samples range in age from Pleistocene to Paleocene and were petrographically classified into five depositional and one authigenic petrofacies: (1) coarse, bioclastic grainstone to packstone, (2) coarse, bioclastic packstone, (3) coated grains, (4) fine, bioclastic packstone, (5) wackestone, and, and (6) dolomite. The coarse grainstone, packstone and coated-grains petrofacies are dominated by >mm-scale bioclastic components indicating deposition in high energy continental shelf environments. These petrofacies show similarities to non-tropical carbonates such as the onshore New Zealand Oligocene Te Kuiti Group limestones. Fine bioclastic packstone and wackestone petrofacies, consistent with bathyal deposition, comprise primarily foraminfera and micrite, similar to Eocene fine-grained carbonates outcropping in New Zealand. The dolomite petrofacies comprises diagenetic dolomite similar to Paleocene and Eocene rocks of the Mead Hill and Amuri Limestone formations. Other post-depositional features are also directly comparable to onshore New Zealand limestones. Despite no clear relationship between age, lithology, or geographic location, this study shows that non-tropical shelf carbonates with subtropical affinities extend north beyond New Zealand (southern Zealandia) to at least 23.7°S latitude. [ABSTRACT FROM AUTHOR]

The aim of this research is to investigate the influence of stratigraphy and structure on the development of present-day topography in the Rangitikei hill country. This is achieved by (1) comparing a new inventory of deep-seated Late Quaternary relict landslide zones to the hydraulic, physical and structural properties of the Whanganui Basin fill, (2) analysing the proximity of landslides to structures and rivers, and (3) exploring the relationships between geology and slope morphology. Analysis suggests postglacial incision and daylighting of the Whanganui Basin fill is a primary control on landslide distribution, providing the necessary conditions upon which a range of triggering mechanisms operate. Faults display a clear relationship to landslide frequency, suggesting earthquakes are possibly an important triggering mechanism. Landscape evolution involves inversion and denudation of alternating coarse and fine-grained sedimentary units. Frequent, shallow landslides dominate on steep, northern scarp slopes, and deep-seated rock planar slides dominate on gentle, southern dip slopes. [ABSTRACT FROM AUTHOR]

Whole rock lithogeochemical data from the andesite rocks which host low-sulfidation epithermal gold veins in the Waihi district, New Zealand have been used to interpret hydrothermal alteration processes that variably altered the andesite rocks. The andesite host rocks are interpreted to have similar primary chemical compositions throughout the Waihi area, as reflected in similar ratios of immobile elements (eg Zr, Ti and other high field strength elements). The geochemical data reveal that elevated K/Al ratios occur in rocks proximal to low-Au–Ag deposits, reflecting adularia alteration in the host rocks associated with the upflowing hydrothermal fluids. Silicification of host rocks is achieved both by the addition of SiO2, as well as the destruction of plagioclase (reflected in the loss of CaO and Na2O). The rocks have been variably altered, with calcite and pyrite abundance reflecting the addition of carbon and sulphur. Pathfinder element (eg As, Sb) concentrations are variable across the district, with high pathfinder element concentrations interpreted to reflect proximity to hydrothermal fluid flow. Together, the results provide a district-scale overview of hydrothermal alteration at Waihi, and emphasise the utility of lithogeochemistry for classifying and quantifying hydrothermal alteration that can then be used to interpret hydrothermal processes and assist mineral exploration. [ABSTRACT FROM AUTHOR]

Since the first official discovery of gold in 1852, gold has been mined in New Zealand from three main types of deposits: placer (c. 19 Moz Au), orogenic (mesothermal; c. 8 Moz Au) and epithermal (c. 11 Moz Au). Currently, gold production in New Zealand is from more than 30 placer mines (>50,000 oz Au per annum) on the West Coast, and in Otago and Southland, and from hard-rock mines at the Macraes orogenic deposits in northeast Otago (202,990 oz Au produced in 2018), and the epithermal deposits of the Waihi area (83,492 oz Au produced in 2018) in the Hauraki Goldfield. The discovery of the Sams Creek intrusion-hosted gold deposit in west Nelson in 1974 has also encouraged exploration for this type of gold deposit. Exploration models for orogenic, intrusion-hosted and epithermal gold deposits have been developed addressing general deposit characteristics, mineral system models and key features for use in exploration. Orogenic deposits are hosted in Western Province Greenland Group (e.g. Reefton Goldfield) and Eastern Province Haast Schist Group (e.g. Macraes), whereas epithermal deposits are associated with Cenozoic volcanic rocks in Northland (e.g. Puhipuhi), and the Coromandel (e.g. Waihi) and Taupo (e.g. Ohakuri) volcanic zones. [ABSTRACT FROM AUTHOR]

More than 80 Cenozoic low sulphidation Au–Ag epithermal deposits and prospects are known in Northland, the Hauraki Goldfield (Coromandel Volcanic Zone) and the Taupō Volcanic Zone of the North Island. Reconnaissance exploration since the 1970s has included magnetic surveys, and stream sediment and rock-chip geochemical surveys. Prospect-scale exploration over the same period has included rock and soil geochemical surveys, magnetic and resistivity/induced polarisation geophysical surveys and drilling, including the study of hydrothermal alteration mineralogy (by thin section and XRD) plus fluid inclusion systematics, to help reconstruct the former hydrothermal system and identify zoning related to mineralisation. Since the 1990s, digital regional exploration and research data sets have enabled GIS-based targeting of prospective areas. At the prospect scale, multi-element ICP and ICP-MS analyses, hyperspectral short wave infrared spectral analyses and portable XRF geochemical analyses of field samples and drill core have been used to complement assay data for identifying spatial trends in geochemistry and mineralogy that help vector to mineral occurrences. Exploration since the 1970s has discovered new Au and Ag resources in extensions of some previously mined deposits (e.g. Golden Cross and Karangahake) and in new deposits in adjacent areas (e.g. Favona, Trio and Correnso in the Waihi area). [ABSTRACT FROM AUTHOR]

The Hauraki Goldfield of the Coromandel Volcanic Zone, North Island, New Zealand, hosts up to 19 known siliceous hot spring deposits, or sinters, some directly associated with Au–Ag ore bodies, in a Miocene–Pliocene, sub-aerial, calc-alkaline volcanic arc overlying Jurassic meta-sedimentary basement. Sinters are surface expressions of predominately adularia-sericite epithermal systems, potentially linked to Au–Ag mineralised conduits at depth. They provide a paleosurface marker to determine the level of erosion, and help determine zones of thermal fluid upflow and/or lateral outflow. Mapped sinters of the Coromandel Volcanic Zone are mainly affiliated with rhyolite domes, occur along structural corridors of the volcanic arc, and contain characteristic textures, mineralogy and pathfinder elements typical of near-neutral pH alkali chloride fluid discharge derived from convectively circulating magmatic fluids diluted by meteoric waters. Textures and trace element compositions of the Coromandel sinters are similar to those of the Taupo Volcanic Zone, New Zealand, and the Jurassic Au–Ag mining districts of the Deseado Massif, Argentine Patagonia. Thus, detailed mapping, textural analysis and trace-element studies demonstrate the prospecting potential of siliceous hot spring deposits for locating ore deposits, and in particular to help define proximal to distal positions relative to vent zones at the paleo-surface. [ABSTRACT FROM AUTHOR]

Epithermal Au-Ag veins of the Hauraki goldfield are mostly hosted by volcanic rocks and are enclosed by extensive zones of hydrothermal alteration that are generally 6–50 km2 in areal extent. The rocks are altered to a variety of hydrothermal minerals; the most common include quartz, adularia, illite, mixed-layered illite-smectite, chlorite, pyrite, calcite, albite and smectite. Some alteration minerals have zoned distributions. Widespread illite grades successively into overlying and bordering illite-smectite and outlying smectite. Significant quartz veins mainly occur in illite-altered rocks, but some can occur in illite-smectite altered rocks. Adularia commonly surrounds veins and can occur in rocks up to >500 m laterally from veins. Ammonium (NH4) minerals, when present, have a restricted distribution occurring laterally <100–300 m from veins. The significance of alteration minerals can be understood from a geothermal context where the system scale zonation of illite, illite-smectite and smectite outline the broad thermal structure of the former hydrothermal system, with illite formed in the hotter portion. Widespread adularia indicates zones of inferred high permeability and the upflow of boiling hydrothermal fluids. Most significant quartz veins occur in rocks altered to adularia and / or illite, restricting the target area, although both minerals can occur >500 m from veins. Where present, NH4-minerals further restrict the target area. [ABSTRACT FROM AUTHOR]

Volcanic-hosted epithermal Au-Ag quartz vein deposits in the Hauraki Goldfield are investigated using a range of geophysical methods. Tools such as airborne magnetics and ground-based resistivity have focussed on mapping alteration zones, lateral contacts in the volcanic rocks, and prospect scale faults. Reviewing the merits of each geophysical method is valuable as it provides exploration teams with the background material required to apply the most effective tools. The review compiles existing data and summarises the rock properties useful for constraining geophysical models. The Golden Cross mine in the Waitekauri Valley is used to illustrate the strengths and limitations of various techniques. Electrical resistivity is the most valuable rock property to target exploration, but magnetic surveying and gamma-ray spectrometry can reduce the ambiguity between quartz-rich mineralised zones and un-altered volcanic host formations. Density and porosity variations caused by alteration can be mapped with gravity data provided the regional field is defined. [ABSTRACT FROM AUTHOR]

The Hauraki Goldfield of the Coromandel Volcanic Zone (CVZ) hosts up to 50 adularia-sericite epithermal Au-Ag deposits that young towards the southeast and align within NNE-to-NE trending structural corridors. We jointly interpret regional aeromagnetic data and a compilation of available geological data to identify structures that have influenced mineralisation. Systematic processing of aeromagnetic data and 'worming' edge detection provides a means of linking deep-seated aeromagnetic patterns with surface geology. The > 80 km long NNW-trending Whangamata-Coromandel lineament that persists to > 3 km depth and the NW-SE-trending Martha-Thames lineament are spatially linked to zones of hydrothermal alteration and epithermal deposits. Similar correlations are seen with deeply sourced NNE-trending lineaments contiguous with shallow sourced anomalies here interpreted as fault-angle basins. Our results are consistent with a model in which inherited basement fabrics appear to have influenced the late Miocene-to-Present tectonic segmentation of the CVZ, with implications for the localisation of epithermal mineralisation. [ABSTRACT FROM AUTHOR]

Thirsty Creek Norite is a small, undeformed, mafic intrusion intruding gneisses of the Granite Hill Complex in the Buller Terrane. An age of 107.1 ± 4.1 Ma has been obtained using Rb-Sr geochronology. A relatively high MSWD of 4.5 is attributed to sericitization and alteration of plagioclase. This date is consistent with other ages for the timing of high-grade metamorphism in the Granite Hill Complex and may represent a metamorphic age, thus providing a minimum age for metamorphism and emplacement of the norite. However, the relatively undeformed nature of the Thirsty Creek Norite suggests it may postdate metamorphism and we speculate that the date could represent a crystallisation age which is contemporaneous with Rahu Suite granitic magmatism in the adjacent Hohonu Batholith. Several geochemical characteristics, including overlapping initial Sr and Nd isotope compositions, suggest the Thirsty Creek Norite could be a relatively mafic yet contaminated melt that is petrogenetically related to Rahu Suite magmatism. Overlaps in the isotopic compositions of the Thirsty Creek Norite and Rahu Suite granitoids therefore imply that any mafic components involved during granitic magmatism must have had relatively enriched isotopic compositions, and that evolution to more felsic compositions occurred without significant interactions with upper crustal components. [ABSTRACT FROM AUTHOR]

Methane-derived authigenic carbonates (MDACs) in Miocene bathyal mudstones in North Island, New Zealand are typically expressed as either sub-seafloor conduit concretions or as seafloor seep limestones, but rarely are both types exposed in outcrop at one locality. Consequently, any potential genetic link between them is usually inferred. This also appears to be the case for global occurrences of MDAC. At the Rocky Knob seep complex near Gisborne both seep limestones and conduit concretions co-occur. The petrography and stable carbon (δ13C) and oxygen (δ18O) isotope compositions of their various authigenic carbonate components (automicrite, fibrous aragonite crystals, and granular, blocky and bladed calcite crystals) show that distinctive isotope and petrographic groupings for precipitates within the conduit concretions match or "correlate" with several of those in the seep limestones. This corroborates their genetic tie and derivation from the same fluids, albeit in different parts (i.e. sub-seafloor vs. seafloor) of the seep complex. [ABSTRACT FROM AUTHOR]

The North Island Fault System (NIFS), coincides with North Island's axial ranges, accommodating crustal strain associated with the Hikurangi subduction margin. Detailed geological mapping along c. 80 km of the NIFS constrains uplift/subsidence and displacement patterns since c. 12 Ma. Uplift within the NIFS area and/or vertical displacement on faults occurred at 12–10, 7–6.5, 5–4.5, 3.5–3.0, 2.5–2, and post-1 Ma. Each deformation episode was associated with vertical offsets across the NIFS of >300–500 m (total c. 5 km). Total dextral strike-slip across the NIFS since 5 Ma is <20 km. Little of the relative plate motion is accommodated on the NIFS (<10%) or in the upper plate (<20%), the majority occurring on the subduction interface. The tectonic evolution of North Island is best explained by reconstructions incorporating vertical axis block rotations and <30 km strike-slip distributed across the entire margin on multiple discrete structures. [ABSTRACT FROM AUTHOR]