Potassium-Argon ages of Tertiary volcanic rocks, Tasmania

F.L, Sutherland; Wellman, Peter

doi:10.26749/rstpp.120.77

Cited by 21 publications

(10 citation statements)

References 8 publications

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“…These rocks are capped on the north bank of Cassidys Creek by a distinct, blocky-jointed coarse basalt, which weathers into red soils. In petrography, this basalt resembles Table Cape teschenite dated at 13.3±0.2 Ma (Sutherland & Wellman, 1986) and yields no zircons from soils panned from its weathered top.…”

Section: Basalt Sequence and Age Datingmentioning

confidence: 79%

“…Here, undated flows occupy valleys, some of which were filled with lavas before deposition of fossiliferous Late Oligocene/Early Miocene marine beds east of Table Cape (i.e. before 25-26 Ma; Sutherland & Wellman, 1986). These are largely alkaline basalts and some carry anorthoclase megacrysts (Geeves, 1982).…”

Section: General Volcanic Settingmentioning

confidence: 99%

“…This flow overlies basal vitric pyroclastics of olivine nephelinite composition, which carry a range of high pressure mantle and lower crustal xenoliths and megacrysts (Sutherland et al, 1989). The Table Cape flow extends west towards Boat Harbour and was dated between 13-14 Ma (Sutherland & Wellman, 1986).…”

Section: General Volcanic Settingmentioning

confidence: 99%

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An unusual Tasmanian Tertiary basalt sequence, near Boat Harbour, northwest Tasmania

Sutherland¹,

Hendry²,

Barron³

et al. 1996

Rec. Aust. Mus.

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ABSTRACT. The mineralogy and petrology of basalts near Boat Harbour, NW Tasmania, are described as this sequence is unusual for Tasmanian Tertiary basalts. The rocks are more sodic and evolved basalts carry more prolific anorthoclase and zircon megacrysts than is normal in Tasmania. Older nephelinites and melilite-nephelinites (26-27 Ma) and younger nepheline hawaiites and mugearites (14-15 Ma) are present and fission track zircon ages (l3-14 Ma and 8-9 Ma) demonstrate that zircon was erupted during and after the evolved basalts. The nephelinites and some evolved basalts carry common spinellherzolite xenoliths, some with rare alkaline reaction veins. Crustal xenoliths are ubiquitous as Precambrian country rocks but include rare 2-pyroxene granulite and anorthosite. Some nephelinites show mariolitic assemblages of olivine, diopsideaugite-aegirine clinopyroxenes, nepheline, sodalite, barian sanidine, ulvospinel, titanian richterite, titanian phlogopite and carbonate.The nephelinites and melilite nephelinite represent primary melts, while the evolved basalts can produce primary basanites by addition of a cumulate wehrlite mineralogy. However, crystal fractionation models for evolving these melts only give inadequate solutions. The low Zr contents, and presence of zircon and anorthoclase megacrysts do not fit into fractionation processes.N ephelinitic geochemistry indicates 4-7% degrees of partial melting of an amphibole-dominated metasomatised garnet peridotite. Low H 2 0+C0 2 contents favour melilite nephelinite melt derived from deeper levels than for the nephelinite melts. Evolved basalts from such metasomatised sources may mark limited fractional crystallisation, while minor early initial melting may produce sodic Zr-rich felsic melts that crystallise anorthoclase and zircon without significant fractionation.The rocks show an isotopic HIMU imprint, but unlike older east Tasmanian basalts lack trace element signatures related to the Tasman Balleny plume system.

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Section: Basalt Sequence and Age Datingmentioning

confidence: 79%

Section: General Volcanic Settingmentioning

confidence: 99%

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An unusual Tasmanian Tertiary basalt sequence, near Boat Harbour, northwest Tasmania

Sutherland¹,

Hendry²,

Barron³

et al. 1996

Rec. Aust. Mus.

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“…). Furthermore, the intrusion penetrated by the Cormorant‐1 well (Table ) was of Miocene age (Sutherland & Wellman, ) suggesting that the vents and sills are temporally related. Our hypothesis is supported by other datasets which also indicate that sills can act as feeders for eruptions (Muirhead et al ., ).…”

Section: Discussionmentioning

confidence: 99%

The architecture of submarine monogenetic volcanoes – insights from 3D seismic data

et al. 2017

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Many prospective sedimentary basins contain a variety of extrusive volcanic products that are ultimately sourced from volcanoes. However, seismic reflection-based studies of magmatic rift basins have tended to focus on the underlying magma plumbing system, meaning that the seismic characteristics of volcanoes are not well understood. Additionally, volcanoes have similar morphologies to hydrothermal vents, which are also linked to underlying magmatic intrusions. In this study, we use high resolution 3D seismic and well data from the Bass Basin, offshore southern Australia, to document 34 cone-and crater-type vents of Miocene age. The vents overlie magmatic intrusions and have seismic properties indicative of a volcanic origin: their moderate-high amplitude upper reflections and zones of "wash-out" and velocity pull-up beneath. The internal reflections of the vents are similar to those found in lava deltas, suggesting they are composed of volcaniclastic material. This interpretation is corroborated by data from exploration wells which penetrated the flanks of several vents. We infer that the vents we describe are composed of hyaloclastite and pyroclasts produced during submarine volcanic eruptions. The morphology of the vents is typical of monogenetic volcanoes, consistent with the onshore record of volcanism on the southern Australian margin. Based on temporal, spatial and volumetric relationships, we propose that submarine volcanoes can evolve from maars to tuff cones as a result of varying magma-water interaction efficiency. The morphologies of the volcanoes and their links to the underlying feeder systems are superficially similar to hydrothermal vents. This highlights the need for careful seismic interpretation and characterization of vent structures linked to magmatic intrusions within sedimentary basins.

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“…There were marine conditions and shaUow water flow from west ro east through Bass Strait. Tect~nically, the region was relatively inactive, other than for danges in latitude due to seafloor spreading, Volcanism was active onshore in Tasmania during the Miocene (Sutherland & Wellman 1986) and also intruded into off~bDre marine sequences (Burrett & Martin 1989). It seems, therefore, that the principal influences on Tasmanian sea-level change and climate were global rather than purely local Only a small proportion of Neogene time is represented by muine sediments recorded here in and around Tasmania and, thus, any reconstruction of Neogene history based on the marine record alone is incomplete and biassed towards short intervals of time.…”

Section: Comparison With Modern Tasmanian Shelf Sedimentsmentioning

confidence: 99%

Marine Neogene Samples from around Tasmania: an extension to the Miocene/Pliocene marine record in Tasmania

Quilty¹,

Telfer²

1994

PPRST

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New Miocene and Quaterna1y foraminiferid faunas have been recovered from previously unrecorded localities onshore near Penguin and Strahan, and at nine offshore localities off northwestern, northeastern and southeastern Tasmania. Most Miocene benthic forms found in these samples are well known from other Tasmanian Tertiary sections but a few previously unreported taxa are recorded in Tasmania for the first time. Two samples from off northeastern Tasmania are Miocene. The sample from southeastern Tasmania is Early Miocene with Quaternary overlying it. Pebbles from Ocean Beach, north of Strahan, contain earliest Middle Miocene faunas. Other samples from off northeastern and northwestern Tasmania contain Quaternary faunas which probably reflect both periods oflower sea level and cool water and also periods of higher sea level and warmer water. These samples extend the range of Miocene calcareous sediments much farther south on both west and east coasts of Tasmania. They also reinforce the pattern of Tasmanian Neogene sedimentation cycles (earliest Early Miocene, latest Early-earliest Middle Miocene, mid Late Pliocene) identified previously.

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Potassium-Argon ages of Tertiary volcanic rocks, Tasmania

Cited by 21 publications

References 8 publications

An unusual Tasmanian Tertiary basalt sequence, near Boat Harbour, northwest Tasmania

An unusual Tasmanian Tertiary basalt sequence, near Boat Harbour, northwest Tasmania

The architecture of submarine monogenetic volcanoes – insights from 3D seismic data

Marine Neogene Samples from around Tasmania: an extension to the Miocene/Pliocene marine record in Tasmania

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