The structure of the Mt Carlton Cu-Au deposit

Transcription

1 Dirks, P.H.G.M., The structure of the Mt Carlton Cu-Au deposit. SYMPOSIUM: New technologies and approaches in mineral exploration. FUTORES II, 4-7 June 2017, Townsville, Qld, Australia The structure of the Mt Carlton Cu-Au deposit P.H.D.M Dirks 1 1 James Cook University, Townsville, Australia paul.dirks@jcu.edu.au Goldfarb (2009)

2 Dirks, P.H.G.M., The structure of the Mt Carlton Cu-Au deposit. SYMPOSIUM: New technologies and approaches in mineral exploration. FUTORES II, 4-7 June 2017, Townsville, Qld, Australia Field mapping P.H.D.M Dirks 1 1 James Cook University, Townsville, Australia paul.dirks@jcu.edu.au Goldfarb (2009)

3 Location Mt Carlton Mt Carlton (From Jell, 2013)

4 Mt Carlton pits V2 A39

5 A39 Pit May 2016 V2 Pit May 2016

6 To date (May 2017), ~4 Mt tonnes of ore have been mined in the A39 and V2 4.87g/t Au, 93g/t Ag and 0.31% Cu g/t Ag from A39 (for 6.16Moz Ag) g/t Au from V2 (for 320 koz Au) Current Reserves stands at g/t Au, 35 g/t Ag and 0.64% Cu (i.e. 733 koz Au, 5,462 koz Ag and 31 kt Cu). The planned mine life is to From: M. Obiri-yaboah 2017

7 Regional Geology Lionel Diggings Mt Dillon Mt Abbot Matrimony ridge Otter ridge Stockyard Creek Tectonic setting: 1. Opening of the northern part of the Bowen Basin Pinnacle Herbert Creek Boundary Boundary Capsize Mt Carlton Castle Strathmore Power Line Ortiz BV8 The Springs Bee Hill Euri Creek Motley Hill Top Ridge Albion Southern 2. NW basin margin structures and ENE, NE and N trending cross Gold Creek Sullivans Reward Quartz Hill Delta Beta BV5 Bowhunters cutting lineaments. 3. Basin inversion in mid- Mount Vista Triassic Oakey Creek Sansons Robard Creek Mt Pool Delvin Pocket from Corral et al (2016) based on Donchak et al (2013)

8 Local Geology Tectonic setting: 1. Volcaniclastic units (Lizzie Creek Fm) in Mt Carlton area dip gently S 2. Qtz-eye porphyry rhyodacite forms favourable host. 3. Mineralisation associated with advanced argillic alteration

9 Age (Ma) Northern Bowen Basin Dating Zircon U-Pb LA-ICP-MS (2015 data) Zircon U-Pb LA-ICP-MS; this (2014 study data) Zircon, SHRIMP, literature Mo Re-Os; Capsize porphyry; this (Chang study 2015) Alunite Ar-Ar; V2; (Chang this study 2015) Trachyte Capsize, late-mineral Basement granitoid Lizzie Creek Volcanic Group Porphyritic intrusions in Lizzie Creek volcanics

10 Lepanto - FSE Models Chang et al (2011) A39-V2? Morrison 2009

11 1 3a 2 3a 4 5a 6

12 Deformation sequence in A39 and V2: D1: High angle normal faulting due to E-W extension: sedimentation mineralisation D2: Normal faulting along low angle detachment faults, with high angle antithetic normal faults due to E-W extension D3: High angle normal faulting due to N-S extension D4: Emplacement of E-W dykes D5: Strike-slip shearing along dyke margins D6: Emplacement of WNW dykes

13 D1: High angle normal faulting due to E-W extension: sedimentation mineralisation Sedimentation and rifting continuous after initial mineralisation events

14 D1: High angle normal faulting due to E-W extension: sedimentation mineralisation

15 D1: High angle normal faulting due to E-W extension: sedimentation mineralisation

16 D1: High angle normal faulting due to E-W extension: sedimentation mineralisation

17 D1: High angle normal faulting due to E-W extension: sedimentation mineralisation

18 D1: mineralisation (V2)

19 D1: mineralisation V2

20 D1: mineralisation A39

21 D1: mineralisation: dickite // L1

22 D1: mineralisation: enargite-pyrite aggregates // L1

23 D1: mineralisation due to E-W extension Bingham solution Axis Eigenvalue Trend Plunge , , , 80.0

24 D2: normal faulting due to E-W extension: S face V2 SW upper benches A39

25 D2: normal faulting due to E-W extension: low angle shear in andesite

26 Tectonic breccia zones associated with low-angle detachments indicative of Large displacements

27 D2: normal faulting due to E-W extension: low angle shear in rhyodacite

28 D2: normal faulting due to E-W extension: mega breccis zones in A39

29 D2: normal faulting due to E-W extension: V2 N face

30 D2: normal faulting due to E-W extension: N-Face

31 D2: normal faulting due to E-W extension: lineations

32 D2: normal faulting due to E-W extension Axis Eigenvalue Trend Plunge , , , 78.0

33 D2: normal faulting due to E-W extension: basement contact

34 D3: normal faulting due to N-S extension

35 D3: normal faulting due to N-S extension

36 D3: normal faulting due to N-S extension: lineations

37 D4-6: dyke emplacement and strike-slip faulting

38 D1 D1 D2 D2 Extensional duplex structures above detachment (examples from Fossen 2011)

39

40 Implications - Mineralization is syn-d1 - Upper volcano-sedimentary units are deposited on top of mineralization - Argillic alteration zones in V2 are not related to mineralization - Mineralization is severely faulted and displaced - D1-D2 and mineralization formed in E-W extensional stress field - During D2 top is moving to the E (i.e. root zones are to the west)

41 Does the distribution of units in this model reflect reality? - units are shear zone bounded - units are discontinuous because of structure

42 How to scale things up and where to look? Distribution of alunite and its 1480 nm peak position

43 Regional Targets The Capsize Trend is a 16km ENE-WSW oriented zone of outcropping silica/clay altered ridges with coincident anomalous geochemistry.