Northwestern Tasmania Research Articles

Volcanology and sedimentology of the host succession to the Hellyer and Que River volcanic-hosted massive sulfide deposits, northwestern Tasmania

The Hellyer and Que River high-grade polymetallic volcanic-hosted massive sulfide deposits of western Tasmania are hosted by a sequence of late Middle Cambrian subaqueous mafic to felsic volcanics and volcaniclastics known as the Que-Hellyer Volcanics. These volcanics occur toward the top of a thicker sequence of mainly felsic volcanics, also hosting mineralization, known as the Mount Read Volcanics.The base of the footwall sequence within the Que-Hellyer Volcanics is marked by massive to pillowed basaltic lavas and volcaniclastics of variable thickness. These are conformably overlain by a thick sequence of andesitic, basaltic, and minor dacitic lavas, and associated volcaniclastics. Eruption of these footwall sequences was rapid, with breaks in volcanism represented only by thin discontinuous epiclastic horizons.A hiatus in volcanism followed the emplacement of the footwall sequences. This hiatus is represented by the deposition of locally derived, coarse-grained mass flows. The distribution and geometry of these epiclastics suggest that they accumulated in local syndepositional depressions. Sedimentation was also accompanied by syngenetic Zn-Pb-Cu-Ag-Au-rich mineralization in the central or axial area of these depressions. Rapid burial by further mass flows assisted in the preservation of mineralization. Shallow intrusive to extrusive dacitic lava flows and domes in the host horizon were emplaced during and immediately after mineralization. Autoelastic material from these dacitic domes was then resedimented and incorporated in the epiclastic horizons overlying the orebodies.Eruption of massive to pillowed basaltic, and minor andesitic, lavas of the Hellyer basalt occurred soon after mineralization and was the final phase of volcanism in the Que-Hellyer Volcanics. The basalts were emplaced as extrusions and as shallow intrusions into wet, fine-grained sediments which began to accumulate above the coarse-grained epiclastic horizons. These basalts buried the remaining parts of the sulfide mound not covered by epiclastics. Immediately after the cessation of volcanic activity in the area, a 100-m-thick sequence of black shales and minor sandstones, known as the Que River Shale, was deposited.The general lack of products of explosive volcanism within the Que-Hellyer Volcanics is most likely a function of the composition of the lavas combined with their emplacement in deep water under high confining pressures. Although the absence of such products does not rule out the possibility of emplacement in shallow-water depths, the absence of abundant large-scale tractional sedimentary structures, the presence of the overlying black, anoxic Que River Shale, and the mass-flow characteristics of elastic units favor a relatively deep water setting for mineralization in the Que-Hellyer Volcanics.

Response of potatoes (Solanum tuberosum cv. Russet Burbank) to band-placed and broadcast high cadmium phosphorus fertiliser on heavily cropped krasnozems in north-western Tasmania

Four field experiments were conducted to examine the yield response and cadmium (Cd) concentration of potatoes (Solanum tuberosum L. cv. Russet Burbank) grown with banded or broadcast phosphorus (P) fertiliser at rates up to 240 kg P/ha. The Cd content of the triple superphosphate (TSP) was 151 mg/kg. All 4 sites were on intensively cropped, high P-fixing krasnozem soils in north-western Tasmania, with concentrations of Colwell-extractable P ranging from 112 to 210 mg/kg. All sites showed economic yield responses to banded P, but broadcast P was much less effective except at the site where the response to banded P was least. Yield responses came mostly through increased tuber number, but at 1 site the tubers were also bigger. There was no effect of P on tuber size distribution or specific gravity. Increasing rates of banded TSP increased tuber Cd concentrations by 50-300% at the 3 sites where they were measured; broadcast TSP had little effect. Tubers from the site with pH 6.0 had much higher Cd concentrations than those from the sites with pH 6.5 and 6.6. Petiole Cd concentrations were about 5 times greater than tuber concentrations.

An Idamean aglaspidid from northwestern Tasmania

An Idamean aglaspidid from northwestern Tasmania

Observations on the sk ulls of fossil and extant echidnas (Monotremata: Tachyglossidae).

The anatomies of four well-preserved, fossilised tachyglossid skulls from Naracoorte, South Australia are described and compared with that of a fossilised skull from north-western Tasmania, with those of 13 extant Long-beaked Echidnas, Zaglossus bruijnii, from New Guinea, and with those of II Short-beaked Echidnas, Tachyglossus aculeatus. The difference in structure and proportions of the rostrums, palates and craniums of the fossil forms from those of Z. bruijnii and T. aculeatus are so great that it is concluded that the former should be placed in a new genus; the name Megalibgwilia is proposed. From the conformation of the rostrum and palate it is suggested that the principal prey of Megalibgwilia was large insects such as scarab and moth larvae, not oligochaete worms as is the case with Z. bruijnii.

The interaction of Cytolin and NAA on cropping red ‘Delicious’ apple

SummaryA trial, at Spreyton in north-western Tasmania, studied the effects of Cytolin and NAA sprays on the thinning and shape of ‘Delicious’ apples. Untreated control and hand thinned trees were compared with trees treated with Cytolin or NAA alone, or in combination. Cytolin was applied at 25 mg 1~‘ at the king petal (KP) stage. NAA was applied at 8 mg I“1 at full bloom (FB) and 7,10, or 15 days after full bloom (AFB). Cytolin alone had no effect on thinning, fruit weight or on pip numbers but it did improve fruit shape. The combination of cytolin and NAA at FB overthinned. Cytolin and NAA combinations applied at all times after FB significantly decreased both mean fruit weight and pip numbers and reduced the percentage of fruit > 70 mm. All Cytolin-NAA combinations and the NAA treatments applied at 10 and 15 days AFB resulted in unacceptably high percentages of apples < 45 mm in diameter (pygmy fruit). It is recommended that Cytolin and NAA should not be used in the same spray programme. NAA alone is a...

Effects of paclobutrazol and carbaryl on the yield of Hi-Early red ‘Delicious’ apples

SummaryA trial at Spreyton in north-western Tasmania compared the effects of paclobutrazol and carbaryl sprays on fruit thinning of apples. Untreated control and hand thinned trees were compared with trees treated with paclobutrazol or carbaryl alone or combinations of both. Paclobutrazol was applied 28 and 49 days after full bloom (AFB). The 28 day AFB paclobutrazol sprays were at rates of either 62.5 or 125 ppm of active ingredient followed by 62.5 ppm 49 days AFB. Carbaryl was applied at 1000 ppm at 10,17 or 24 days AFB. Although several treatments removed more fruit than the controls, only two treatments thinned to less than the desired crop load, represented by the hand thinned treatment. These overthinned treatments were combinations of paclobutrazol applications and carbaryl sprayed 24 days AFB. It is recommended that if paclobutrazol programmes are to be initiated 28 days AFB, that carbaryl should not be sprayed later than 17 days AFB. Also, if carbaryl is sprayed late it is preferable to use pacl...

A calcian ralstonite-like mineral from the Cleveland Mine, Tasmania, Australia

AbstractA calcium-rich ralstonite, forming colourless octahedral crystals up to 2 mm across, occurs in a F-rich assemblage at the Cleveland Mine, northwestern Tasmania. Other minerals present include well-crystallized morinite, gearksutite, vivianite, siderite, K-rich feldspar (adularia), fluorite and quartz. The F-rich assemblage probably formed during greisenization when Na and F-rich magmatic brines reacted with enclosing carbonate host rocks to produce hydrothermal Na-Ca-Mg-bearing solutions. Chemical analysis of the ralstonite-like mineral gave a formula (Na1.47Ca0.52)(Mg1.49Al0.55P0.04)F6 [(OH)0.43O0.36F0.21)].This differs from the ‘pyrochlore’ formula, due to the substitution of Ca + (OH,O,F) for H2O, in addition to the coupled substitution of Na + Mg for Al in ‘normal’ ralstonites. The Cleveland Mine ralstonite has the highest recorded Ca, Na and Mg contents. While the mineral is likely to be a new species on chemical grounds, single crystal X-ray photographs indicate the structure is disordered, possibly composed of small compositional domains.

An Upper Cambrian (Idamean) dendroid assemblage from near Smithton, northwestern Tasmania

Twelve species of dendroid graptolites belonging to three families are described from the Upper Cambrian (Idamean) of the Smithton Trough, northwestern Tasmania. Taxa include species assigned to the genera Dendrograptus, Dictyonema, Aspidograptus, Desmograptus, Callograptus, Polygonograptus, Palaeodictyota, Thallograptus, Mastigograptus, Archaeolafoea, and Aellograptus. New species include Aspidograptus smithtonensis sp. nov., Desmograptus quiltyi sp. nov., Callograptus praesalteri sp. nov., and Polygonograptus mellaensis sp. nov. Polygonograptus is proved to be a member of the Dendroidea, and together with Aspidograptus, Palaeodictyota, Thallograptus, Callograptus and Aellograptus, is recorded for the first time from Tasmania. Polygonograptus, Palaeodictyota and Thallograptus are recorded from the Cambrian for the first time. New information on rhabdosomal shapes and inferred palaeoecological adaptations is presented.

Triassic sandstone petrology of Tasmania: evidence for a Tasmania-Transantarctic basin

Similar fluvial sequences of Triassic age occur in Tasmania and the Transantarctic Mountains of Victoria Land. The Tasmanian reference section at Poatina consists of Lower Triassic quartzose fluvial sandstones overlain by Middle and Upper Triassic volcaniclastic fluvial sandstones and shale containing coal. Similar, but less wel1-exposed sequences, occur in many places in Tasmania and in southern Victoria Land. The hypothetical Tasmania-Transantarctic basin was similar in scale, configuration, and history to the Sydney foreland basin. Palaeocurrent data suggest that streams flowed along the axis of the basin from Antarctica to Tasmania. Lower Triassic sandstones were deposited by braided streams, but Middle and Upper Triassic stream deposits change from braided to meandering downstream towanl Tasmania. Quartzose sandstones in the Lower Triassic were derived from northwestern Tasmania and the East Antarctic craton. The source of volcaniclastic sandstones in the Middle and Opper Triassic was a calcalkaline volcanic arc along the palaeo-Pacific margin.

Tin-bearing greisens of Mount Bischoff, northwestern Tasmania, Australia

The large Mount Bischoff tin deposit occurs within an inlier of Precambrian sedimentary rocks which are surrounded by lower Paleozoic and Tertiary sedimentary and volcanic rocks. Tin is contained within a network of altered Devonian porphyry dikes (endogreisens), replaced dolomite (exogreisen), mineralized hydrobreccias, thin veins, and alluvials.Greisen-style alteration of porphyry dikes is zoned inward and downward from nearly fresh beta -form quartz + K-feldspar dike material through muscovite + fluorite + or - tourmaline greisen and topaz + quartz greisen to quartz greisen. Tin grades of up to 2 wt percent occur within endogreisen, with higher grades occurring near the topaz + quartz-quartz greisen contact.Replacement of dolomite by greisen assemblages and greisen-style alteration of porphyry dikes were cogenetic. The mineral assemblages and the spatial distribution of greisen minerals, such as mica, topaz, and tourmaline, in endo- and exogreisens are similar. Topaz, quartz, fluorides, cassiterite, and tourmaline occur in endo- and exogreisen, although the proportion of fluoride minerals (sellaite and fluorite) is high where dolomite is replaced. Within exogreisens the highest grades of Sn occur at the contact between topaz-bearing endo- and exogreisens, grades obtained from drill core range up to 22 wt percent (1.3-m intersection).The greisens were overprinted by assemblages containing phyllosilicates (chlorite, talc, phlogopite, serpentine, phengite), carbonates (magnesite, siderite, dolomite), abundant sulfides (pyrrhotite + or - pyrite, sphalerite), late fluorite, and later argillic alteration. Only limited quantities of dolomite were replaced by these later postgreisen assemblages.Fluid inclusion temperatures range from 90 degrees to near 500 degrees C, with the greisen being produced between approximately 340 degrees to 420 degrees C or higher and the later overprints at progressively lower temperatures. Salinities at the greisen stage of mineralization were high, with measurements commonly between 30 to 40 percent total dissolved salts. Ca-Na-K-Fe-Mn chlorides, possible fluorides, CO 2 , and hydrocarbons(?) were deduced as components of the fluid phase. Lesser amounts of dissolved Si, Al, and B and rare Ti, Ca, La, P, Sn, Cu, and S were inferred from daughter mineral identifications.The deposit was formed from acidic and relatively reduced hydrothermal solutions in subvolcanic conditions, at a depth of approximately 1 km, above a leucogranite pluton (granite inclusions exist in the dikes). High-level brecciation was cogenetic with porphyry dike intrusion and both occurred in several separate intrusion-mineralization cycles.

The Weld River Group: a major upper Precambrian dolomite sequence in southem Tasmania

The Weld River Group is a folded Precambrian sequence (several kilometres thick and predominantly of dolomite) that crops out in the northern Jubilee region, southern Tasmania. It overlies older predominantly siliciclastic sequences with paraconformity or angular unconformity that does not correspond to any major (cleavage-forming) tectonometamorphic event in the older successions. The group consists of a basal, relatively thin, siliciclastic unit (the Annakananda Formation), locally overlain by an impersistent pebbly mudstone (the Lake Timk Formation), followed by massive, fine-grained dolomite (the Gomorrah Dolomite), then bedded dolomite largely consisting of catagraphic, oolitic grainstone (the Devils Eye Dolomite), and then a second massive dolomite unit (the Styx Dolomite). In faulted contact with these units is a probably younger sequence of massive dolomite intercalated with dolomite-derived mixtite, mudstone and sandstone (the Cotcase Creek Formation). The older Precambrian siliciclastic sequences and the Weld River Group are unconformably overlain by a lithicwacke and conglomerate succession, probably of Middle or Upper Cambrian age. The stratigraphic setting of the group, and some lithologic features, suggest correlation with upper Precambrian dolomitic sequences in northwestern Tasmania (e.g. Black River Dolomite, Success Creek Group) implying that the Penguin Orogeny may be absent or only weakly manifested in the Jubilee region.

Henry Hellyer, Esquire, 1790–1832 Van Diemen's land company surveyor in his footsteps

Abstract This is an historical article about an area of north-western Tasmania known as the Surrey Hills and the first European to set foot upon them, a surveyor named Henry Hellyer. Although arguably the most well-known of early Tasmanian land explorers, little attention has been paid to his toils as the surveyor, architect-cum-engineer and superintendent of works. In the form of a journey both back through time and across country, this article reveals a little about him and this aspect of his life and works in association with “the Hills”.

Residual effects of limestone on pasture yields, soil pH and soil aluminium in a krasnozem in north-western Tasmania

Residual effects of 15 t/ha of surface applied limestone were evaluated at Elliott in northwestern Tasmania on a clover-based, perennial dryland pasture that was well fertilised and sufficient in molybdenum. The soil was a krasnozem (Gn 4.11) with a mean pH of 5.5. Annual pasture DM increases of 0.5-1.7 t/ha persisted for at least 9 years after the final application of limestone. The largest seasonal DM increases of 0.4-0.7t/ha were recorded in autumn. No decline in the pH of the surface 75 mm of the unlimed plots was detected. However, the pH of the surface 75 mm of the limed plots declined by 0.09 pH units per year from pH 7.0. The decline in surface pH was due to the movement of the zone of maximum limestone effect on pH from the 25-50 mm depth to the 100-125 mm depth, a distance of 75 mm in 8 years. Average soil pH profiles, CaCl2-extractable aluminium and root DM distribution in the surface 300 mm did not indicate that aluminium toxicity was restricting pasture DM production on the unlimed plots. However, toxic concentrations of exchangeable aluminium (extracted with BaCl2) were recorded below 100 mm in the unlimed plots.

Regeneration characteristics of a swamp forest in northwestern Tasmania

The botanical composition and regeneration characteristics are described for a Melaleuca ericifoliaLeptospermum lanigerum forest from northwestern Tasmania. The size classes of the two dominant species are highly correlated with tree age. Size class analysis shows that the dominants are regenerating continuously. The relationship of this forest type to rainforest and wet sclerophyll forest are discussed.

Effects on milk production of feeding wheat supplements to grazing dairy cows in early lactation

Two herds, each of 19 Friesian cows, were run on separate farmlets in north-western Tasmania. One herd (NW) grazed pasture only, and was estimated to be receiving 75% of potential intake, while the second herd (W) received 3.0 kg coarsely hammermilled wheat per cow, daily for 42 days during early lactation in addition to pasture. Although the feeding of wheat increased total feed intake, there was no significant difference between the groups in either daily milk yield (21.5 v. 21.8 L cow-1), milk fat yield (1.1 v. 1.09 kg cow-1), liveweight change (0.05 v. -0.2 kg cow-l) and herbage intake (12.0 v. 12.0 kg DM cow-1 day-1) of cows or of pre- (1.77 v. 1.8 t DM ha-1) and post- (1.31 v. 1.32 t DM ha-1) grazing mass, on farmlets NW and W respectively. We conclude that the feeding of wheat did not increase milk production or improve liveweight change under the conditions of this experiment.

Stratigraphy, pollen analysis and paleoclimatic interpretation of Mowrray and Rroadmeadows Swamps, North Western Tasmania

SUMMARY Sedimentary, palynologic and 14C analysis of marls and swamp‐peats, formed under fluctuating artesian spring conditions, provide climate and vegetation records from >52,000 to 0 yr BP at Mowbray, and 30,000 to 0 yr BP at Broadmeadows. Before about 65,000 yr BP conditions at Mowbray were relatively dry and the vegetation was Leptospermum shrubland. After 65,000 and before 55,000 yr BP moist conditions produced Cyperaceae swamps. Between 55,000 and 45,000 yr BP the climate was relatively dry, and between 45,000 and 35,000 yr BP relatively moist. Leptospermum shrubs were dominant in both periods. The climate was moist between 35,000 and 22,000 yr BP and sedge swamps formed. Between 22,000 and 11,000 yr BP the climate was relatively dry and grasses were important. Postglacial climate (11,000–0 yr BP) was warm and moist, and Melaleuca‐Leptospermum forest and shrubland flourished. The climatic changes suggested for north western Tasmania seem to compare broadly with changes suggested for Tasmanian and f...

The application of geophysics to the discovery of the Hellyer ore deposit, Tasmania

In August 1983, a drill hole aimed at a deep conductor in Northwestern Tasmania intersected 24 m of high grade base and precious metal mineralization at a depth of 120 m. This intersection proved to be the small, shallow end of the 15 Mt Hellyer deposit (Sise & Jack 1984; Eadie & Silic 1984). The ore body is covered by greater than 100 m of volcanics, making the story of its discovery technically impressive.

Reproduction in dairy cattle: Effect of age, cow condition, production level, calving-to-first-service interval and the ‘male’

A study was conducted to determine the effect of various factors on the reproductive performance of approximately 1700 cows in 12 seasonally calving dairy herds in North Western Tasmania. Submission rate (percent of cows submitted for service for the first time in the first 24 days of the mating season) rose from 60% to 97% as cow condition score improved from 3 to 5.5. There was no effect on non-return rates (percent of cows submitted for service for the first time in the first 24 days of mating which did not return to service in the subsequent 21 days), provided condition score was 3.5 or over. Milk fat yield was positively correlated to both submission and non-return rate until milk fat yield exceeded 1.0 kg/day when both fell (from 79% to 71% and from 73% to 38%, respectively). Non-return rate was 46% when the calving-to-first-service interval was less than 40 days after which it rose to a more normal 65%. Submission rates were unaffected by calving-to-first-service interval. There was a significant positive correlation between age and non-return rate, but not between age and submission rate, although submission rate also tended to be higher in older cattle. The proportion of cows having short cycles (less than 18 days) was 18%. In contrast to reports in other species, the presence of the male did not improve oestrous detection or non-return rate of cows in the immediate post-partum period.

A further large magnesite deposit along the Savage River in northwestern Tasmania

A further large magnesite deposit along the Savage River in northwestern Tasmania

Exanthem in northwestern Tasmania

Exanthem in northwestern Tasmania