2771353
Persistent Identifier: https://pid.geoscience.gov.au/sample/AU2771353
| Property | Value |
|---|---|
| id | 2771353 |
| igsn | 10273/AU2771353 |
| sample_id | ERIVMAE1463.01 |
| eno | 628624 |
| sampling_feature_name | ERIVMAE1463 |
| sampling_feature_type | field site |
| sample_type | outcrop specimen |
| sampling_method | outcrop sampling |
| material_class | rock |
| earth_materials | Y |
| stratigraphic_unit | Bethungra Formation |
| geological_province | Central NSW - Omeo Province |
| sample_remark | Mauve to purplish-brown, crystal-poor rhyolite containing about 10% sand-sized feldspar and quartz crystals and fragments, interpreted as a volcaniclastic rock. The matrix is aphanitic and locally displays weak banding. In thin section, this sample is an extremely altered ignimbrite. Crystals and crystal fragments constitute 7% of the rock, and comprise quartz, K-feldspar and plagioclase in subequal abundance. Some crystals are broken, but many are not. K-feldspar is altered to brown clay minerals, and plagioclase to sericite. Quartz is variably embayed. Rare ferromagnesian minerals are less than 1 mm and altered to iron oxide minerals, but rare pseudomorphs with prismatic- and diamond-shaped outlines suggests the primary phase was amphibole. The unit is part of a package of sandstone, conglomerate, shale, rare felsic volcanic rocks and rare limestone in the NE corner of the Tarcutta 1:100 000 area. In aeromagnetic imagery, the package is part of an elongate fault-bounded block up to 2 km wide that extends NW until it becomes contiguous with the geophysical domain of the Early Devonian Bethungra Formation (Warren et al., 1995; Eastlake, 2018). Stratigraphic control is provided by the limestone horizons, where fish remains indicate a Pragian (mid-Early Devonian) age (Pickett et al., 1984). Felsic volcanic rocks encompass moderately crystal-rich, feldspar-quartz phyric coherent rhyolite, to juvenile, poorly-sorted, fine-sand to medium-pebble size rhyolitic breccia. Juvenile clasts in the breccia are closely packed, angular, and vary from jumbled to jigsaw-fit textures. The matrix consists of translucent microcrystalline silica (Eastlake, 2018). This rock was targeted for U-Pb SHRIMP geochronology to compare isotopic dates from magmatic zircon with the biostratigraphic constraints. A similar sample from the same unit, collected at Blackball Hill quarry 13 km to the NW, yielded a maximum age of 416.6 +/- 2.3 Ma for deposition (ERIVMAE1821.01). |
| structural_measurements | None |
| inorganic_geochemistry | Y |
| organic_geochemistry | None |
| geochronology | Y |
| isotope_groups | None |
| hydrochemistry | None |
| rock_properties | None |
| mineralogy | None |
| thin_sections | None |
| repository_samples | Y |
| mineral_deposit_samples | None |
| mineral_deposit_waste_samples | None |
| linked_files | None |
| other_geological_data | None |
| project_name | None |
| gda94_longitude | 147.976713 |
| gda94_latitude | -35.112727 |
| sample_originator | Geological Survey of New South Wales (GSNSW) |
| date_acquired | 2017-06-05 00:00:00 |
| Links |
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