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1.
The Cape Hoskins volcanoes form part of the Quaternary volcanic island arc that extends from Rabaul in the east to the Schouten Islands in the west, and they overlie the northerly dipping New Britain Benioff Zone. The products of the volcanoes range in composition from basalt to rhyolite, and are normative in quartz and hypersthene. They contain phenocrysts of plagioclase and subordinate augite, hypersthene, and in most samples iron‐titanium oxides; some samples also contain olivine or quartz or both, and some pumice contains hornblende and, rarely, biotite.

Chemical analyses of 29 volcanic rocks are presented; 22 were also analysed for 17 minor elements — Rb, Ba, Sr, Pb, Zn, Cu, Zr, Y, Ni, Co, Sc, Cr, V, Ga, B, U, and Th.

Chemically the rocks have many of the characteristics of the ‘island arc tholeiitic series’, but do not show a pronounced relative enrichment in iron and appear to be relatively enriched in Sr. Compared with volcanic rocks from the northern part of the Willaumez Peninsula, they are lower in K (but not Na), Ti, Rb, Ba, Zr, Pb, Th, Ni, and probably also V, Cu, and Zn: these differences are attributed to the greater depth of the Benioff Zone beneath the Willaumez Peninsula. The more basic of the Cape Hoskins rocks are similar in most respects to lavas of comparable composition from Ulawun volcano to the east.  相似文献   

2.
An early Ludlovian (early eβ1) to early Gedinnian (early eγ) age is assigned to the Cliftonwood Limestone—Elmside Formation strata of the Yass Basin, New South Wales. Several Australian sequences are correlated with the Yass Basin succession.  相似文献   

3.
During the Cainozoic there was widespread volcanism, mainly basaltic, in eastern New South Wales. Numerous new K‐Ar ages, together with previously published results, provide information on the age of virtually all the main volcanic provinces, and indicate that the volcanism started about 70 m.y. ago in the Late Cretaceous, and was continuous from about 60 m.y. ago (Palaeocene) until about 10 m.y. ago (middle Miocene). There has been no volcanic activity since 10 m.y. ago.

The ages of uplift of the Eastern Highlands are estimated from the relationship of the dated basaltic flows to the topography. A major uplift is deduced some time between the mid‐Cretaceous and late Oligocene, followed by a quiescent period. A further uplift started some time after the middle Miocene, and it continues to the present day. The highland was uplifted differentially both along and transverse to the axis.  相似文献   

4.
34S/32S ratios have been measured in a suite of samples from the stratabound, volcanogenic massive sulphide deposit at Woodlawn, N.S.W. 34S values for the sulphides vary as follows: in the ore horizon, pyrite +6.7 to +9.2%. (mean +8.1‰), sphalerite +5.2 to +8.6‰. (mean +6.9‰), chalcopyrite +6.4 to +7.0‰ (mean +6.7‰) and galena +2.8 to +5.5‰ (mean +4.4‰); in the vein mineralization, the host volcanics—pyrite +8.7 to +11.4%. (mean +9.8‰), sphalerite +7.8 to + 10.3‰ (mean +9.2‰), chalcopyrite; +8.8 to +10.1‰ (mean +9.2‰) and galena +6.9 to +7.2‰ (mean +7.1‰). Barite from the upper ore horizon levels has an isotopic composition of +30.0‰, consistent with its having originated from Silurian ocean sulphate. The general order of 34S enrichment in the sulphides is pyrite > chalcopyrite sphalerite > galena. Isotopic fractionations in the systems galena/sphalerite/pyrite and chalcopyrite/pyrite indicate an equilibration temperature of 275–300°C. This temperature is considered to represent that of sulphide deposition.  相似文献   

5.
Zircons from two igneous and two sedimentary units in the Bombala area of southeastern New South Wales have been examined by the sensitive high resolution ion microprobe (SHRIMP) to establish a timeframe in which to interpret these rocks. Previous studies have correlated these rocks with Late Devonian units of the south coast, solely upon the basis of stratigraphy and lithology as palaeontological evidence was absent. The two igneous units are the Hospital Porphyry and Paradise Porphyry occurring beneath the sedimentary units. Both give a Frasnian age that can be correlated with the Boyd Volcanic Complex. The sedimentary samples are from the basal and upper sections of the Rosemeath Formation, a fluvial ‘redbed’ consisting of conglomerate, coarse sandstone, and associated red siltstone and mudstone. Detrital zircons from the basal conglomeratic section at Kilbrechin indicate a dominant provenance from local Silurian granites and volcanics and a maximum depositional age that can be correlated with the Frasnian‐Famennian Merrimbula Group. However, detrital zircons from the upper coarse sandstone section of the Rosemeath Formation at Endeavour Lookout challenge the positive correlation trend with a lack of Silurian‐age grains and a presence of grains ranging from Late Devonian to Early Carboniferous in age. These results imply either that the south coast correlation is not valid for the upper sequences, or that the Merrimbula Group sequences also extend upward into the Carboniferous. The general coarseness of the Rosemeath Formation also suggests a relatively local provenance. No Early Carboniferous source is known in the immediate vicinity suggesting that Early Carboniferous igneous activity in this region of the Lachlan Orogen may have been more extensive than is currently realised.  相似文献   

6.

Basalt at Sassafras was erupted in the Middle Eocene. The K‐Ar ages average 45.3 ± 4.9 Ma on whole rock and 48.4 ± 1.9 Ma on plagioclase. The basalt is not limited to a plateau capping, but extends 150 m down into adjacent valleys. Comparison with nearby Eocene basalts shows that there was in excess of 250 m of local relief in the central Shoalhaven valley by the Early Tertiary. The basalts were extruded at high elevation, and denudation of the coastal margin of the upland was already well advanced. Post‐basaltic denudation has been very slow, and the Early Tertiary landscape is well preserved.  相似文献   

7.
Seismic sections and the analysis of lithostratigraphic units from well-log data were used to develop a new stratigraphic correlation of the Winduck, Snake Cave and Ravendale Intervals for the Blantyre Sub-basin. The stratigraphic boundaries of the intervals were defined at marked changes in well-log characteristics, and depth estimates of the boundaries were derived from the well-log data in Mt Emu 1, Blantyre 1 and Kewell East 1. Six seismic-stratigraphic boundaries have been identified in the seismic sections to show the continuity of the latest Silurian to Holocene sediments throughout the Blantyre Sub-basin; from bottom to top they are: H-1, base of the Winduck Interval; H-2, base of the Snake Cave Interval; H-3, base of the Ravendale Interval; H-4/5 base of the undifferentiated Upper Carboniferous/Permian sediments; and H-6 base of the undifferentiated Cenozoic sediments. All stratigraphic boundaries are based on good continuous markers, with strong amplitudes throughout the whole sub-basin. A three-dimensional geological model was developed from the seismic data to map out the geometry of the key reflectors, and hence the structure and stratigraphy of the Winduck, Snake Cave and Ravendale Intervals in the areas where these intervals have been preserved. This model has better defined the Wilcannia High and two smaller highs around the Mt Emu 1 and Snake Flat 1 wells, and further defines the relationships between the stratigraphy, sub-basin geometry and development of complex structures in the Blantyre Sub-basin.  相似文献   

8.
The southern part of the Sydney Basin of New South Wales is comprised mainly of Permian and Triassic marine to freshwater clastic sedimentary rocks. Within this sequence there are six latite extrusive units, several medium‐sized monzonite intrusions and a large number of small to medium‐sized basic to intermediate intrusions. Thin basaltic flows were extruded onto the Tertiary topographic surface. All of these rocks are relatively undeformed.

Radiometric (K‐Ar) dating has previously been carried out on Mesozoic and Tertiary intrusions and flows of the southwestern portion of the Sydney Basin. However, relatively few Permian, and no post‐Permian, K‐Ar dates have been published for the southeastern portion of the basin. The present investigation provides nine K‐Ar dates from the latter area.

Four extrusive and intrusive units have been confirmed as Permian in age (238 ± 6; 241 ± 4; 245 ± 6; and 251 ± 5 m.y.). Five post‐Permian (on stratigraphic criteria) intrusions yielded Tertiary ages (26.2 ± 3.0; 47.9 ± 2.5; 49.0 ± 4.0; 49.4 ± 2.0; and 58.8 ± 3.5 m.y.). The Permian ages agree with previously published K‐Ar data from the southeastern Sydney Basin, and the Tertiary ages complement and extend the data from the southwestern portion of the basin. However, no Mesozoic K‐Ar dates were obtained from the southeastern Sydney Basin. The Tertiary intrusions may have been emplaced as a result of rifting between Australia and New Zealand, or between Australia and Antarctica, or both.  相似文献   

9.
Conodont species Iapetognathus fluctivagus and Iapetonudus ibexensis are documented for the first time from Australia. The former is the primary marker internationally defining the base of the Ordovician, and the latter is also a distinctive species previously recorded only from the base of the Ordovician in North America. Both species were recovered from a single sample in the Kandie Tank Limestone of the Kayrunnera Group, located about 50 km west of White Cliffs in far western New South Wales. Other species recovered from this sample include Prooneotodus spp., Cordylodus lindstromi, Cordylodus proavus, Hirsutodontus simplex, Teridontus nakamurai and Variabiloconus sp. Recognition of the Iapetognathus fluctivagus Biozone in the Kandie Tank Limestone supports its correlation with the Green Point section (Global Stratigraphic Section and Point for the base of the Ordovician) in western Newfoundland and the Lawson Cove section of Utah (Auxiliary Stratigraphic Section and Point), as well as sections in Asia and South America. Review of other sections in Australia and elsewhere spanning the Cambrian–Ordovician boundary confirms that, in the absence of I. fluctivagus, the presence of C. lindstromi is a good proxy for this level.  相似文献   

10.
The volcanogenic Woodlawn Cu‐Pb‐Zn sulphide mineralization occurs within a low‐grade metamorphosed sequence of Middle to Upper Silurian felsic volcanics and fine‐grained sedimentary rocks. Studies on a total of 234 rock samples from diamond drill holes have delineated zones of hydrothermally altered rocks extending more than ~500 m laterally from the main ore lens, at least ~100 m into the foot wall and up to ~200 m into the hanging wall. These altered rocks contain virtually no remnants of primary feldspars and ferromagnesian minerals, and they are variably chloritized, sericitized and silicified. Chlorite and disseminated sulphide minerals are most abundant in zone I, a restricted zone of intense alteration immediately around the main ore lens, whereas sericitic muscovite is most abundant in the relatively extensive zone II, further from the ore. Silicification is also a feature of volcanics well beyond the limits of observed phyllosilicate‐rich alteration zones. Chemical changes within the hydrothermally altered rocks include major enrichment of Fe, Mg, S, Si and H2O, more sporadic enrichment of Ag, Ba, Bi, Cd, Cu, Mn, Pb, Sn and Zn, and major depletion of Ca, Na and Sr. K is depleted in zone I and shows considerable variation, but no overall depletion or enrichment, in zone II.

Lithological, mineralogical and geochemical features around the Woodlawn orebody are basically similar to those associated with the younger, unmetamorphosed Kuroko deposits.  相似文献   

11.
The recent discovery of dickite, intimately associated with ordered and disordered kaolinite, in quartzose sandstones and conglomerates of the Illawarra Coal Measures is of interest since in terms of the phase rule the co‐existence of two or more of these polytypes is evidence of either an unstable or metastable assemblage. A study has, therefore, been undertaken of the host rocks and accompanying strata in an attempt to gain insight into the mechanism of formation of the dickite and the reason for its development in preference to either of the other generally more abundant polytypes. From the results it would appear that although much still remains unresolved, the dickite is authigenic and precipitated from migrating groundwaters. Due probably to unusually low concentrations of silica in the groundwaters the rate of precipitation was inordinately slow and this apparently facilitated growth of relatively coarse crystals and development of the most stable phase.  相似文献   

12.
From new data on coastal and continental shelf morphology, sediments, stratigraphy and chronology, it is possible to formulate a general model of late Quaternary marine sedimentation, for New South Wales and southern Queensland. This model integrates various factors influencing deposition in coastal and shelf environments, in relation to glacio‐eustatic sea level oscillations.

The model involves several components, including (i) very slow to negligible continental margin subsidence during the Quaternary, (ii) an inherited geomorphic framework; (iii) oscillations of sea level of c 100 m amplitude every 100 000 years, with interglacial high sea levels being close to present and only the Last Interglacial being significantly higher; and (iv) a wave climate that induces a potential south to north littoral sand transport at all sea level positions.

Terrigenous sediment that is moved from the hinterland through embayments to the shelf is either stored as barrier, estuarine or inner shelf deposits, or lost to depositional sinks on the continental slope or into coastal dune fields. Over many glacial‐interglacial cycles, sand has been progressively moved northward and has accumulated in vast aeolian sand deposits in southern Queensland. Littoral sand transport was especially effective during sea levels lower than present. The relatively shallow and lower gradient shelf north of Newcastle (33°S) has encouraged preservation at the coast of a wide range of depositional morphologies, including Pleistocene barriers, whereas the steeper southern shelf has induced net sediment loss seawards and shoreline erosion, excpt in the Holocene. To account for Holocene barrier development in the southern region, the model invokes reworking of sand deposits stranded high on the inner shelf at the end of the Pleistocene Epoch. These were in disequilibrium with Postglacial marine processes that operated at a lower level of the sea than did those during the Last Interglacial maximum.  相似文献   

13.
Ground‐penetrating radar (GPR) has been used on an array of floodplain types on the lower Tuross River, in southeastern New South Wales, as part of an investigation into controls on channel‐floodplain relationships. Ground‐penetrating radar transects from two floodplains are presented, along with sedimentological detail from trenches dug along the profiles at key locations. Sedimentological investigations showed that 100 MHz antenna gave an approximation of overall bedding trends in the upper 3 m when automatic gain control processing was used. Spreading and exponential compensation processing provided insight into textural changes associated with increased silt content distal of the levee crest. One trench showed that thinning beds were responsible for onlapping reflectors. Signal attenuation at ~4 m depth below the raised floodplain surface resulted from a >50 cm‐thick bed of sandy clay. The close integration of GPR and sedimentological data produced an excellent dataset, that enabled form‐process associations and floodplain evolution to be established for these sandy floodplains. However, accurate subsurface assessment and interpretation must stem from carefully combined GPR and sedimentological datasets.  相似文献   

14.
The stratigraphic succession of formations in the Myall district comprises in ascending order the Bunyah Beds, Wallanbah Formation, Kataway Mudstone, Boolambayte Formation (new names), Nerong Volcanics (E'ngel, 1962), Booti Booti Sandstone, Yagon Siltstone, Koolanock Sandstone, Muirs Creek Conglomerate (new names) and Alum Mountain Volcanics (Engel, 1962). The units range in age from possibly Devonian to possibly Permian, most being Carboniferous. The Mograni (new name), Tugrabakh (Voisey, 1940) and Mayers Flat Limestones (new name) are members of the Wallanbah Formation. The Violet Hill Volcanics (new name) is a member of the Yagon Siltstone. The Burdekins Gap Basalt Member and Lakes Road Rhyolite are members of the Alum Mountain Volcanics.

Environments of deposition range from nonmarine (Nerong Volcanics, Alum Mountain Volcanics, Muirs Creek Conglomerate, upper part of Koolanock Sandstone) through shallow marine (Booti Booti Sandstone, lower part of Koolanock Sandstone, calcareous parts of Wallanbah Formation) to deep marine (most other units). Facies relationships indicate a progressive deepening of the sedimentary environment to the east throughout most of the Carboniferous sequence. The Tournaisian sequence is readily correlated with a similar sequence in the Rocky Creek and Belvue Synclines. Higher units are correlated with sequences at Gloucester (Campbell & McKelvey, 1972) and Booral (Campbell, 1962).  相似文献   

15.
The geological map of the Broken Hill area in New South Wales shows a striking feature, the Grasmere Knee Zone, which consists of a major change in structural trend. North of the Grasmere Knee Zone, the analysis of the structure of the Late Silurian–Early Devonian Mt Daubeny Basin coupled with AMS measurements suggests that the basin has undergone two phases of folding. Correction of magnetic data from bedding orientation has consisted in unfolding sequentially fold F2 to obtain a simple syncline and unfolding fold F1. Although the fold tests, conglomerate test and dyke test may be considered to be positive concerning the high-temperature component (DAU-CH), paleomagnetic results from the Mt Daubeny Formation (locality DAU) are subject to caution, in particular due to the complex unfolding procedure. If component DAU-CH, carried by hematite, is interpreted to be primary in origin, the corresponding paleopole is consistent with an X-type of apparent polar wander path for Gondwana, in particular if one relies on the proposed optimum bedding correction. South of the Grasmere Knee Zone, the Mt. Daubeny Formation is considered to be rotated clockwise relative to the north. The tentative model presented herein proposes that a block corresponding to the Southwestern Subprovince of Lachlan Orogen indented the Tasmanides between the Central Subprovince of the Lachlan Orogen and the Delamerian Orogen from the mid-Devonian (Tabberabberan event) up to the Early Carboniferous, triggering rotations in the Broken Hill area. A later magmatic event, thought to be Early Cretaceous, may have induced fluid migration and deposition of magnetite leading to the occurrence of an important magnetic overprint (DAU-CM).  相似文献   

16.
The Jindabyne Thrust has been mapped south of Lake Eucumbene, along the eastern side of Lake Jindabyne and thence southwards to the gorge of the Snowy River in Byadbo Lands. It is marked by a crush zone and a west‐facing scarp. Structure contours on the Thrust where it enters the gorge of the Snowy River in the Byadbo region indicate an easterly dip of about 20°.

The north‐south erosional valley now occupied by Lake Jindabyne is controlled by the Thrust and the gorge below the Jindabyne Dam has been rejuvenated by recent movement.

The nature of the Jindabyne Thrust and other faults in the Jindabyne‐Berridale region can be deduced from their effects on the Silurian granitoid plutons. Where a pluton, circular or elliptical in plan and with vertical walls, is transected by a thrust, a semi‐elliptical or semi‐circular shape results; granitoid rock types cannot be matched across the fault. Wrench faults in the region either curve into or are transected by the thrusts, depending upon the geometrical relationships of both.

It is suggested that the north‐south dividing line between granitoids derived from igneous rocks (I‐types) to the east and granitoids derived from metasedimentary rocks (S‐types) to the west is a major tectonic feature of eastern Australia. The line coincides with a transition from a regime where wrench faulting predominates to one dominated by thrust faulting. These changes in both tectonics and granitoid lithology suggest that the I‐S line marks the eastern boundary of crystalline basement, possibly of Precambrian age.  相似文献   

17.
This paper provides the first palynological data from four Upper Cretaceous localities from the Islands of Hvar and Šćedro (southern Croatia), in the central part of the Adriatic Carbonate Platform. Studied material represents palynomorphs produced by coastal vegetation and transported to the shallow marine platform areas. Determined vegetation includes diverse hygrophilous, understory vegetation, range of evergreen needle trees attributable to Pinaceae and Podocarpaceae, as well as Araucarian conifers; ginkgo, cycads and/or bennettites. Flowering plants were likely represented by herbaceous forms. The palynoflora is generally indicative of a temperate, warm and humid climate. The occurrence of the Normapolles group with the presence of Plicapollis sp. and Pseudoculopollis sp. point to Turonian or probable Turonian–Coniacian age, and represent the southernmost record of occurrence within the Normapolles palynological province. Dominance of angiosperms and low abundance of ferns suggests an early-Late Cretaceous age. These findings are supported by the micropaleontological analyses and previously determined age of the sauropod dinosaur footprints described on the Island of Hvar. Based on the paleobotanical and palynological data, the dinosaur diet probably included araucarian conifers, ginkgo and angiosperms, and ferns to a lesser extent.  相似文献   

18.
The presence of base‐metal mineralization at Woodlawn was first recognised early in 1968 when a roadside reconnaissance geochemical sampling survey, conducted over felsic volcanic rocks in the Goulburn‐Tarago area, encountered anomalous B horizon soils containing up to 200 ppm Cu, 800 ppm Pb and 300 ppm Zn. Regional soil thresholds have been determined at 50 ppm Cu, 90 ppm Pb and 50 ppm Zn. Chip samples from the subsequently located gossan revealed up to 2000 ppm Cu, 8000 ppm Pb and 2000 ppm Zn, 500 ppm Sn, 25 ppm Ag and 3000 ppm As.

The first grid B horizon soil geochemical survey was conducted in 1968 over the gossan and surrounding area, and repeated with closer spaced sampling in the first half of 1970. The first survey delineated strong Cu (to 1000 ppm) and Pb (to 2500 ppm) anomalies coincident with the gossan zone, and intense hydromorphic zinc anomalies (to 3000 ppm) located down slope from the gossan in residual clay‐soils derived from dolerite bedrock. Threshold values have been determined at 140 ppm Cu, 700 ppm Pb and 580 ppm Zn. Ag and Sn in B horizon soils show pronounced anomalies coincident with the gossan and are suitable metals for geochemical target definition. Of fourteen trace elements determined in 1974 from B and C horizon soils on two lines across the ore zone Cu, Pb, Zn, Se, Ba, Sn and Ag show direct correlation with the mineralization, whereas Cd and Mn show moderate hydromorphic dispersion, having accumulated principally in clay soils derived from dolerite weathering. As, Sb and Bi, whilst responding over the ore zone, show elevated values in soils over hanging‐wall units; Ni and Co show maximum levels in soils over dolerite bedrock.

Bark and leaves of Acacia mearnsii, collected from a line across the gossan, contain anomalous levels of Cu, Pb, Zn, Sn and Ti near the ore zone, and weaker, but clearly anomalous Mn and Ni levels over dolerite bedrock. Both bark and leaves of Acacia mearnsii reflect the presence of concealed mineralization. The shrub Solanum linearifolium grows preferentially over and close to the Woodlawn ore zone, where it contains up to 840 ppm Cu, 250 ppm Pb, 7300 ppm Zn, 6 ppm Sn and 250 ppm Ti in leaf ash compared with levels of 200 ppm Cu, 2 ppm Pb, 400 ppm Zn, 0.8 ppm Sn and 60 ppm Ti in plants growing 1.5 km from the ore zone. This shrub has potential as an indicator of base‐metal mineralization.  相似文献   

19.

Strontianite (SrCO3), witherite (BaCO3) and alstonite (CaBa[CO3]2) were among the range of epigenetic coal cleat/fracture carbonates identified within the Wittingham Coal Measures, Jerrys Plains Subgroup in the Hunter Valley. Three stages of diagenetic cement development, all related to basin evolution, are postulated. Material for the development of the various carbonates was derived from: basinal pore fluids, surrounding rock and organic matrix as a result of diagenetic exchange, active mass transport or devolatilization of basement rocks during metamorphism, including plutonic intrusion.  相似文献   

20.

The Barry Granodiorite is a weakly deformed I‐type, and the Sunset Hills Granite is a moderately deformed S‐type, granite. Both granites were passively intruded into an already foliated greywacke and volcanic sequence. Emplacement may have been facilitated by faults related to the oblique opening of the late Early Silurian Hill End Trough. The granites display a dominant foliation which formed during the late Middle Devonian and subsequently was reoriented during the Early Carboniferous. The Barry Granodiorite and Sunset Hills Granite are on the margin of north‐south ductile shear zones related to the Wyangala Batholith. These granites and the adjacent Carcoar Granodiorite have undergone reorientation during movement on ductile shear zones either due to megakinking during late‐stage north‐south shortening, or southeastward movement of the southern margin of the west‐northwest‐trending Lachlan Transverse Zone.  相似文献   

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