2771362
Persistent Identifier: https://pid.geoscience.gov.au/sample/AU2771362
| Property | Value |
|---|---|
| id | 2771362 |
| igsn | 10273/AU2771362 |
| sample_id | ERIVSJT0048.01 |
| eno | 628631 |
| sampling_feature_name | ERIVSJT0048 |
| sampling_feature_type | field site |
| sample_type | outcrop specimen |
| sampling_method | outcrop sampling |
| material_class | rock |
| earth_materials | Y |
| stratigraphic_unit | Ranchero Granite |
| geological_province | Central NSW - Omeo Province |
| sample_remark | Porphyritic granite with abundant K-feldspar phenocrysts up to 4 cm, intergrown with 1 cm quartz, coarse-grained biotite, and a rectangular elongate mineral (mostly replaced by secondary muscovite and biotite), in a fine- to medium-grained quartzofeldspathic groundmass. The altered mineral was identified in thin section as andalusite (K.F. Bull in Trigg, 2018). In thin section, this porphyritic biotite-andalusite granite has perthitic K-feldspar phenocrysts up to 15 mm, and quartz phenocrysts up to 7 mm. Plagioclase has sericite-altered cores. Fine-grained biotite is about 3% of the rock, and hosts abundant radioactive inclusions. Muscovite is interstitial, indicating either late crystallisation or a secondary origin. The groundmass is quartzo-feldspathic, and fine- to medium grained (0.5-1.5 mm). Fine-grained striated andalusite shows pale-pink pleochroism, and is altered to muscovite. In places, euhedral andalusite and muscovite growth indicates cavities infilled with 'last gasp' fluids. Spots and cracks in andalusite are recrystallised to corundum, which is separated from quartz by muscovite. This indicates high Al activity, and local Si depletion. Late quartz and muscovite in cracks and as inclusions indicate incipient greisenisation. The mineralogy and texture indicate crystallisation in dry, low pressure, low-Fe conditions. This biotite-andalusite granite is part of the newly-defined Ranchero Granite. Trigg (2017) regarded it as an extension of the 428.7 +/- 1.8 Ma Ganmain Granite (Bodorkos et al., 2015) along strike to the SE. However, the Ranchero Granite is only 2 km SW of the 414.7 +/- 2.3 Ma Ardlethan Granite (Bodorkos et al., 2013) at Bald Hill. The Ranchero Granite is also spatially associated with the subvolcanic I-type 418.8 +/- 2.2 Ma Boblegigbie Granite (Bodorkos et al., 2016; Blevin, 2019) 6 km to the S. Bodorkos et al. (2018) associated the Boblegigbie Granite with earliest Devonian felsic volcanic rocks of the Gurragong Group. |
| 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 | 146.82354 |
| gda94_latitude | -34.448597 |
| sample_originator | Geological Survey of New South Wales (GSNSW) |
| date_acquired | 2018-05-09 00:00:00 |
| Links |
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