ID  - b7be415c-a6d4-4e5c-86f0-1b8b39059887
TY  - RPRT
T1  - Summary of results. 40Ar/39Ar step-heating hornblende dating, Johnnies Reward prospect, Strangways Range, Aileron Province
A1  - McGloin, MV,
A1  - Matchan, E,
A1  - Phillips, D,
PY  - 2018///
Y1  - 2018/
AB  - This Record details 40Ar/39Ar step-heating analysis of hornblende sampled from the polymetallic Cu-Pb (Zn-Ag-Au) Johnnies Reward prospect, ALICE SPRINGS, in Aileron Province, central Australia. A sample of hornblende (AS15MVM034) was collected from an outcropping quartz vein associated with pegmatite intrusions that cross-cut the Cadney Metamorphics and mineralisation at the prospect. Hornblende was dated to determine the timing of vein formation and any potential overprinting episodes of fluid-flow and/or metamorphism. If the quartz vein is pegmatite-related, any age yielded may date pegmatite emplacement. Because the sampled quartz vein cross-cuts the mineralised host assemblage, dating of the hornblende will also constrain a minimum age for mineralisation at the prospect.
AB  - Hornblende from sample AS15MVM034 produced a discordant age spectrum of anomalously old apparent ages of ca 3.8 -1.6 Ga for the low-temperature steps (steps 1-3), decreasing to ca 900-800 Ma (steps 4-5), and then to ~650 -600 Ma for the remaining 55% of the gas release profile (steps 6-12). Inverse isochron ages for the same sample (making no assumption about initial 40Ar/36Ar sample values) produced concordant data for the mid- to high-temperature (steps 6 to 12), and revealed the presence of excess argon in the sample. This indicates that age spectrum ages (which are calculated assuming an atmospheric initial 40Ar/36Ar ratio) are verestimated. The inverse isochron age generated through steps 6 to 12 is 428 ± 31 Ma (2s; MSWD = 1.6, probability of fit = 0.16). This age is consistent with the timing of the ca 450-300 Ma Alice Springs Orogeny and provides a minimum age constraint for mineralisation at Johnnies Reward.
T2  - NTGS Record 2017-013
SN  - ISBN9780724573240 (PDF)
SN  - ISSN1443-1149
UR  - https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/86862
PB  - Northern Territory Geological Survey
M3  - NTGS Record
ER  -