摘要:

As part of an evaluation of the geothermai resources of Fiji, measurements of conductive heat flow were made in boreholes at nine sites on the two main islands, Viti Levu and Vanua Levu. These are believed to be the first published land measurements from this part of the Pacific. On Viti Levu, heat flow was found to be about 50 mW/m2in the south, and about 90 mW/m2in the north.On Vanua Levu, the heat flow near Savusavu was anomalously high (140 mW/m2).Geological and other geophysical evidence suggest that a heat source in the form of an intrusive body is heatmg a geothermal reservoir of meteoric water. At Labasa,a near-normal value of 59 m W /m2was obtained.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422272

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Two main styles of basement can be defined beneath the sediments in Solander Trough, south of New Zealand, on the basis of seismic reflection character.Basement beneath the SoIander Basin (i.e., the eastern limb ofSolander Trough) is predominantly a smooth, planar surface, regarded as a peneplain oflate Cretaceous-early Tertiary age, cut on mainly plutonic igneous rocks.This surface may ex te nd westward to the zone where the Fiordland Boundary Fault is inferred to project offshore, although in the Waitutu Sub-basin the basement is deeply buried and probably broken by faults. In contrast, the basement in western Solander Trough, beneath Balleny Basin, is irregular in relief and variable in character.It is proposed that the irregularity of basement preserved in Balleny Basin reflects structural dislocation, erosion, and subsequent burial in the period from Cretaceous to Eocene.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422273

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cenozoic sedimentary rocks assoeiated with volcanies in Carnley Harbour inelude: (1) Camp Cove Conglomerate, largety volcanic-derived as debris flows, with rare granitic and metamorphie elasts, and probably of Late Oligoce to earliest Miocene age; (2) Musgrave Formation (new formation) of marine limestone, grit, tuff, quartzofeldspathic sandstone, and interealated volcanics of Middle Miocene age – these two formations are of shallow-water and subaerial origin and are unlike Cenozoic sequences elsewhere on the Campbell Plateau; (3) thin fluvial sequences higher in the Miocene volcanie sequenee between flow rocks; and (4) Quaternary till

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422274

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Camley Harbour, at the southem end of the Auckland Islands (l66°E, 50°51'S), is a dissected Miocene shield volcano formed on basement continental crust of the Campbell Plateau. Subaerial, marine, and glacial erosion excavated a section through ftows and pyroclastics of the volcanic pile to expose a swarm of dikes and sills which intersect the lowest lava flows, underlying Middle Miocene sediments and basement granite of Cretaceous age.A coarse-grained, crudely layered biotite gabbro intruding the volcanic succession is exposed at McClure Head and Circular Head and probably represents a partially unroofed magma chamber.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422275

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Five phases of deformation are recognised in the schists of the Mt Aspiring area, northwest Otago, New Zealand.The first two phases resulted in isocIinal ductile folding and macroscopic nappe formation during greenschist facies metamorphism. The third phase, which occurred during waning metamorphic conditions, resulted in tight folding, with east-west overthrusting of macroSCOPIC nappes.Ouring this third phase, earlyformed fold axes in high-strain zones were rotated towards the stretching or translation direction. The fourth deformation phase is characterised by chevron folds (on all scales) with north-trending axes and associated west-dipping thrust faults.The Moonlight Fault, a major regional feature.is associated with this phase of deformation. The fifth phase of deformation involved mesoscopic conjugate sets of crenulations with east- and southeasttrending axes. Steeply dipping, fold axial surface joints developed in these crenulations are commonly intruded by lamprophyric dikes or associated carbonate veins.Several phases of deformation have characteristic quartz c-axis fabrics.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422276

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Metamorphic K-feldspars (or90ablO), from the western part of the Alpine schist in Copland Valley, display optical properties indicating average structural states ranging from potassian intermediate sanidine to intermediate microcline. P/T conditions during K-feldspar production were about 510-570°C at 7 kbar.Records of high-temperature assemblages elsewhere in the Alpine schists indicate that metamorphic conditions in the western part of the schist belt were as high as the kyanite zone.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422277

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Potassium-argon ages are reported for mineral and total-rock sampies from the progressively metamorphosed Haast Schist sequence in the Haast valley, Haast Pass, Lake Wanaka, and Lake Hawea areas of Otago, South Island. These rocks extend from low-grade (chlorite zone greenschist facies) near Lake Hawea, through medium-grade (biotite and gamet zone greenschist facies) in the Haast valley, to high-grade (amphibolite facies) near the Alpine Fault. The ages of total-rock and micas show a general eastwards decrease from the Alpine Fault in three zones. (I) More than 25 km east of the fault, the ages increase steadily from 120 to I 73 Ma near Lake Hawea. These ages are interpreted as a cooling age pattern resulting from continued slow uplift, which began after the main (Rangitata) metamorphism at least 173 Ma aga (mid Jurassic) and which continued until at least 120 Ma aga (mid Cretaceous). (2) In a transitional zone, between 15 and 25 km from the fault, the mineral and totalrock ages increase rapidly eastwards from about 20 Ma to 120 Ma. It is possible that these ages may also be a cooling age pattern, reftecting the continuation of uplift at a much slower rate throughout the late Cretaceous and Cenozoic, but it is more probable that the ages represent a section in the metamorphic sequence where only partial accumulation of argon has taken place while buried at depth.(3) In a narrow 10 km zone adjacent to the fault, the mica and total-rock ages are very young (12–30 Ma) but the coexisting hornblende and plagioclase ages are very widely discordant (40-1600 Ma).This indicates that excess argon is definitely present in the plagioclase and hornblende and possibly throughout the rocks as a wh oie. Amounts of excess argon in the high-grade schists are 1-4 nljg, and they decrease westwards to less than 0.5 nljg in the biotite zone greenschist facies and to zero amounts in the chlorite zone greenschist facies rocks.Graphical display of the K and40Ar (radiogenic) contents of the K-poor and K-rich mineral phases suggests that the excess argon was uniformly distributed throughout the rocks during an isotopic rehomogenisation event 12 ± 5 Ma aga (Miocene-Pliocene). This young age must reftect the time of the last uplift of the Haast Schist near the Alpine Fault during the formation ofthe Southern Alps. It is suggested that this uplift phase during the Kaikoura (Miocene-Recent) orogeny was sufficiently rapid and localised to cause some heating during shearing, and consequent radiogenic argon loss from micas, and re-incorporation under a high argon partial pressure into coexisting K-poor phases such as plagioclase and hornblende.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422278

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Scheelite, gold, and sulphide mineralisation is found in sheeted and stockwork vein systems thought to be vertically above (Kirwans Hili), around, and within greisenised granite cupolas (Bateman Creek) of(?)Devonian-Carboniferous age. These granitic bodies intrude metasediments of Ordovician age (Greenland Group), within a zone of structural weakness trending NNW.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422279

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

North Kaipara Barrier is formed by sediments, mainly estuarine and dune sands of the Kaihu Group, deposited in a major cyc1e of transgression (subsidence) and regression (uplift) during the Quatemary. Hautawan, Okehuan and younger lignites along with terrace surfaces at 105 m, 67 m, 40 m, 24 m, 8 m and 4-2 m a.s.l., which can be correlated with dated surfaces elsewhere in the North Island, provide chronologie control. Five units, the Hautawan DargaviIle Formation, Nukumaruan- Castlec1iffian Rototuna Formation, Castlec1iffian- Hawera Pareotaunga Formation, Hawera South Head Formation, and the Hawera Shelly Beach Formation, are present. The barrier has changed littie since the end ofOkehuan time when the major existing valleys were cut in Rototuna sediments.Upper Pleistocene terrace surfaces are locally preserved within these valleys.Undifferentiated Hawera and Holocene deposits are also present on the barrier.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422280

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Boreholes and offshore seismic profile surveys in southern Evans Bay, WelIington Harbour, indicate that a drowned river valley has been partly infilled with sediments during two glacial interglacial cycles. The original valley was probably eroded along the shatter zone of a late Pliocene fault situated on the eastern side of the bay. The infilling sediments include two assemblages: (I) interglacial age (including Holocene) shelly marine sands and muds, which have a palynoflora from flourishing rimu-podocarp forest, and (2) g1acial age gravelly and carbonaceous terrestrial deposits, wh ich have a palynoflora dominated by grasses or, in slightly milder times, by beech and manuka. Postdepositional deformation of early Holocene sediments may indicate either further faulting along the shatter zone of the Pliocene fault or an effect of sediment compaction during earthquake stress. Deformation of late Holocene sediments is interpreted as differential compaction and slumping being a secondary effect of earthquake shaking.

ISSN:0028-8306    

DOI:10.1080/00288306.1985.10422281

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor