2678314
Persistent Identifier: https://pid.geoscience.gov.au/sample/AU2678314
| Property | Value |
|---|---|
| id | 2678314 |
| igsn | 10273/AU2678314 |
| sample_id | NSWSJAF0166.01A |
| eno | 621280 |
| sampling_feature_name | NSWSJAF0166 |
| sampling_feature_type | field site |
| sample_type | outcrop specimen |
| sampling_method | outcrop sampling |
| material_class | rock |
| stratigraphic_unit | felsic volcanics and high level intrusives 42173 |
| geological_province | Cobar Basin |
| sample_remark | This sample was collected from a roadside exposure of freshly excavated dacitic porphyry near the locality of Gindoono, about 50 km N of Condobolin. This porphyry intrudes the I-type Majuba Volcanics, and has generated a wide hornfels zone in the enclosing volcano-sedimentary rocks. The Majuba Volcanics have not been dated directly; however, the unit is interfingered with first-cycle volcaniclastic rocks of the Baledmund Formation (Downes et al., 2016; Gilligan and Suppel, 1978), which have yielded a maximum age of 419.3 +/- 2.8 Ma for deposition (Bodorkos et al., 2015). An Early Devonian (c. 420 Ma) age for the Majuba Volcanics would also be in keeping with the ages of similar nearby I-type volcanic centres, such as the 418.9 +/- 2.5 Ma Babinda Volcanics (Waltenberg et al., 2016), the 421.7 +/- 2.3 Ma Florida Volcanics (Black, 2005), and the Mineral Hill Volcanics (422.2 +/- 3.7 Ma, 428.2 +/- 3.9 Ma: Spandler, 1998; 417.6 +/- 3.2 Ma, Downes et al., 2016). This sample was dated to establish a minimum age for the host Majuba Volcanics, and other I-type volcanic and plutonic units in the Nymagee area. In thin section, this porphyritic dacite features K-feldspar–plagioclase and quartz phenocrysts up to 5-6 mm long, in a very fine-grained quartzofeldspathic mosaic-style matrix. Clots (up to 1–2 mm long) of red-brown biotite, intergrown with titanite and opaque oxide minerals, appear to replace a primary ferromagnesian phase. Fine-grained biotite is distributed throughout, giving the matrix a spotted appearance, and its textural preservation implies the biotite is hydrothermal in origin, rather than having grown during contact metamorphism. Slender to stout apatite crystals are an accessory phase. A locally well-developed foliation is defined by realigned matrix biotite. |
| earth_materials | Y |
| 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 | 146.9385533 |
| gda94_latitude | -32.6628011 |
| sample_originator | Geological Survey of New South Wales (GSNSW) |
| date_acquired | 2017-08-30 00:00:00 |
| Links |
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