2771354
Persistent Identifier: https://pid.geoscience.gov.au/sample/AU2771354
| Property | Value |
|---|---|
| id | 2771354 |
| igsn | 10273/AU2771354 |
| sample_id | ERIVMAE1594.01 |
| eno | 628625 |
| sampling_feature_name | ERIVMAE1594 |
| sampling_feature_type | field site |
| sample_type | outcrop specimen |
| sampling_method | outcrop sampling |
| material_class | rock |
| earth_materials | Y |
| stratigraphic_unit | Bangus Formation |
| geological_province | Central NSW - Omeo Province |
| sample_remark | Dark greenish-grey, foliated and metamorphosed, mafic-looking rock. In outcrop, the foliation is defined by elongate feldspar-rich lenses up to 1.5 x 8 mm, interspersed with medium-grained (0.5-3.0 mm) mafic porphyroclasts that comprise 15% of the rock. Euhedral amphibole is prominent in some porphyroclasts. In thin section, this deformed, poorly sorted mafic metasandstone contains relict detrital plagioclase (20%), ferromagnesian mineral grains (8%), and rare lithic clasts, in a dynamically recrystallised matrix. It is compositionally immature, and termed an arkose based on porphyroclast content. Plagioclase is the most abundant relict detrital component, and includes subangular to subrounded grains, as well as unmodified prismatic crystals. Brownish-green hornblende forms subangular to subrounded grains, some with simple twins. Epidote pseudomorphs replace subequant mineral grains less than 1.5 mm across, some of which preserve eight-sided cross sections, and may have been calcic pyroxene. Lithic fragments are commonly rounded. A continuous secondary foliation defined by fine-grained actinolite, chlorite, minor epidote and opaque oxide minerals wraps the porphyroclasts, and indicates that deformation occurred under greenschist facies conditions. Eastlake (2018) assigned these rocks to the mid-Silurian Bangus Formation (which includes the 'Bangus volcaniclastics' of Wyborn, 1996). W of Adelong, a metamorphic aureole in the Bangus Formation (Eastlake, 2020) reflects emplacement of the 432.0 +/- 1.9 Ma Wondalga Granodiorite (ERIVMAE1820.01), ostensibly imposing a minimum age on the Bangus Formation. The compositional immaturity of the Bangus Formation implies a proximal source region of intermediate composition. One candidate is the 432.1 +/- 2.1 Ma Junawarra Volcanics (ERIVMAE1221.01) which abuts the Bangus Formation to the NE; another is the Nacka Nacka Metabasic Igneous Complex, for which Glen (2013) cited an unpublished U-Pb LA-ICPMS zircon date of 438 +/- 3 Ma. |
| 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 | 147.963778 |
| gda94_latitude | -35.25237 |
| sample_originator | Geological Survey of New South Wales (GSNSW) |
| date_acquired | 2018-05-10 00:00:00 |
| Links |
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