Tick Hill university study.

Good afternoon everyone.

This has just been sent through to me by one of the professors involved with the Tick Hill study at the James Cook University in Townsville.
He said all results were now in the public domain and could be accessed through EGRU or QDEX.

As you can see, I've copy and pasted the first few pages.
Perhaps someone could do a better job at uploading the entire PDF document.



"The Tick Hill gold deposit Final Report

Project Title: Geological setting of the Tick Hill Au deposit, NW Queensland, Australia
Project Number: 17071-JCU-01
Reporting period: 27 November 2017- 15 December 2020 (final report)

Project Team JCU: Truong Le (PhD candidate): August 2017-ongoing
Prof. Paul Dirks,
Dr. Ioan Sanislav,
Dr. Jan Huizenga

This report has been prepared for:
Department of Natural Resources and Mines (State of Queensland)
- Dr. Helen Degeling: [email protected]
- Dr. Vladimir Lisitsin: [email protected]

This report has been prepared by:
Prof. Paul Dirks: [email protected]
Truong Le: [email protected]
Dr. Ioan Sanislav: [email protected]
Economic Geology Research Centre (EGRU)
College of Science & Engineering
James Cook University, Townsville, Australia 2 | P a g e


TICK HILL EGRU-JCU REPORT DEC 2020: PART 1 - INTRODUCTION

The Tick Hill gold deposit

The Tick Hill Gold Deposit is situated at 21º 38’N - 139º 55’E, 110 km SSE of Mount Isa in NW Queensland, Australia. Whilst Cu-Au deposits are common in the Mt Isa block, gold grades are generally less than 1-2 g/t, and gold-rich deposits are rare (e.g. Duncan et al., 2011;
Denaro et al., 2013). One notable exception to this is the Tick Hill gold deposit in the southern part of the Mary Kathleen Domain. Although the Tick Hill deposit presents a mineralization style of great interest to exploration companies, little is known about the deposit other than that it is a gold-rich, shear-hosted hydrothermal deposit (Denaro et al., 2013) that has been interpreted as a possible end-member IOCG deposit (e.g.Groves et al., 2010). Tick Hill was discovered in 1989, and was mined over a short period of time (1991-1995). Partly because the deposit was developed so quickly, no detailed studies have been published on the deposit or its style of mineralization. Apart from several student theses (Tedman-Jones, 1993; Watkins 1993; Choy, 1994) and some shot overview articles (Forrestal et al., 1998), few details about the deposit are available in the public domain. The overall aim of this report was to correct this situation.

The Tick Hill deposit was high grade and mineralization occurred almost entirely as free gold with little to no silver, making it extremely profitable when mined. These characteristics, along with the general paucity of sulphides and associated metals (e.g. Cu, Co) as well as the high-grade metamorphic host rocks, make Tick Hill a unique, gold-rich deposit in the Mount Isa Inlier. This report provides details on the geological setting and mineralization style of the Tick Hill deposit based on mapping, core logging and petrography.The work presented here was designed as a PhD project in the Economic Geology Research Centre (EGRU) at JCU, undertaken by Mr Truong Le, and combines new petrological, geochemical, mapping and geochronological results, with materials from past exploration reports.

Main Findings

1. Structural setting

 The Tick Hill ore body occurs in strongly sheared (i.e. mylonitic) high grade gneisses, that were deformed at upper amphibolite facies during early (1800-1770 Ma) composite deformation events D1 and D2, and overprinted by a series of greenschist facies to lowergrade D3 events between 1600-1520 Ma. The D3 events included a pervasive fluid alteration event that caused regional albite-chlorite-hematite alteration and moved gold around 1525 Ma.
 The ore body is linear and plunges west at ~55°, parallel to the intersection lineation between E and NNE trending D3 fault zones, and close to the orientation of the D1mineral extension lineation.
 The ore zone parallels a D1 foliation truncation plane that was reactivated as a W-down sinistral-normal fault during D3.
 The high-grade ore zone transgresses lithological boundaries, but most of the gold is hosted in D3 altered, D1-2 quartz-feldspar mylonite.
 The high grade ore zone has a limited lateral and vertical extent and is sharply bounded.
 The main D1-2 shear zone hosting the gold formed between ~1770-1790 Ma. Reactivation of the shear zone during D3 together with regional alteration and gold re-mobilisation occurred around ~1520 Ma.

2. Host lithologies

 The stratigraphy that hosts the Tick Hill deposit was intruded by ~1780 Ma granites in the Tick Hill region and ~1850 Ma granites 4 km west of Tick Hill. This strongly suggests that the calc-silicate units hosting the tick Hill deposits do not belong to the Corella or Arylla formations, but are part of the Kalkadoon-Leichardt Suite. There is a possibility that various lithostratigraphic units are complexly inter-leaved and infolded in the Tick Hill area.
 The hanging wall quartzite unit varies in composition and displays banding with quartzonly, magnetite-rich, biotite-rich, scapolite-chlorite amphibole-rich and feldspar-rich layers. Zircon dating, zircon geochemistry, zircon morphologies and textural evidence strongly suggest that much of this quartzite is secondary in nature and probably represents a silicified D1 high strain zone, as originally suggested during exploration campaigns.

3. Timing of mineralisation

 Textural evidence indicates that gold was mobile during a number of different stages in the evolution of the deposit.
 In some mineralised amphibole-rich units, coarse-grained gold is contained as inclusions inside hornblende and diopside aligned in the main S1-2, high-grade fabric. This provides evidence that at least some of the gold formed early (pre- or syn-D1-2).
 Gold is largely contained in quartz-feldspar mylonite which probably originated as migmatitic melt intrusions around ~1775Ma, indicating that gold was mobilised during deformation/metamorphism around ~1770-1780 Ma.
 A bi-modal grainsize distribution for gold is common in which coarse grains aligned in the main mylonitic fabric are surrounded by a ‘halo’ of finer grains suggestion localised remobilisation.
 Much of the gold occurs in close association with early D3 (stage 2) fractures and associated chl-ep-hbl/act alteration. Gold also occurs in association with later D3 fractures (stage 3 and 4) and carbonate veinlets. This clearly indicates that gold was mobile during D3.
 On balance, textural and chemical evidence suggests that most of the gold originated early (during or prior to D1) and that it was remobilised late (during D3).

4. Conditions of formation

 Early D1 peak assemblages in garnet-bearing amphibolite record conditions of ~10 kbar and 680 °C. Near the pit, peak conditions recorded in hornblende are ~5-6 kbar and 500-600 °C. These conditions were probably attained during D2 and/or the earliest stage of D3(stage 1).
 Chlorite thermometry indicate that during D3, when gold was mobile, alteration temperatures progressively decreased from ~380 °C (early stage 2) to ~120 °C (stage 4).
 Metamorphic pressures during D3, when gold was mobile, changed from ~3kbar during stage 2 to <1kbar by stage 4; i.e. gold mobilisation during D3, was associated with exhumation of the rocks in an extensional environment.
 Fluid inclusions from quartz grains that enclose gold are dominated by hydrous (H20-only), liquid-vapour inclusions with variable vapour content (0-90%), and solid inclusions of cubic halite (with a volume range that suggests that the salinity of the fluids was high), CaCl2 and hematite. These characteristics indicate that the main fluid component during D3 experienced phase separation (i.e. boiling) at the time of formation and that the fluid was hydrous, saline, strongly oxidizing and probably acidic. This fluid was capable of moving metals like Au, Cu and Co.

5. Ore mineralogy

 Mineralisation consists of pure gold, with few associated metals. Ag values are generally well below 1%.
 Exploration assay data indicates that high-grade gold zones correlate with Ag, Bi, Pd and Pt. There is no correlation with Cu, Co, As, Sb, Pb and Zn or any other element.
 Exploration assay data indicates gold does not correlate with Na, Fe, Ca or K, which are elements involved in D3 alteration.
 One characteristic feature of the Tick Hill deposit is the presence of Bi-selinides in the high-grade ore zone, and the general paucity of sulphides. Texturally early sulphide appears to have been partly resorbed during the earlier stages of D3 (stage 2) with some re-deposition (together with calcite, selenides and re-mobilized gold) during later stages of D3 (e.g. stage 4).
 Copper appears to be elevated in a shell (mainly the footwall) peripheral to the highgrade ore zone. Copper enrichment was probably primarily lithologically controlled (with higher Cu and more chalcopyrite in more mafic lithologies).

6. Deposit style

 The main issue with the Tick Hill deposit is that it is unclear when it originally formed.
 There is clear evidence that coarse-grained mineralisation must have formed relatively early (pre- to syn-D1) and that the gold was mobile during several of stages in D3.
 What is not clear, however, is whether the gold was introduced during D3, or whether gold and an earlier alteration halo including magnetite formed earlier, and were remobilised and dispersed during D3.
 Earlier studies such as Williams et al. (2005) and Groves et al. (2010), have interpreted Tick Hill as a gold-rich end-member IOCG deposit. To assess this more closely we have listed criteria for IOCG’s as presented in Williams et al. (2005) and Groves et al. (2010), and we have assessed how Tick Hill fits these criteria. Many of these criteria are based on observations made on IOCG’s in the Eastern Fold Belt of the Mt Isa block.

A typical IOCG deposit Tick Hill

1.Cu with or without Au as an economic metal There is no major Cu mineralisation at Tick Hill and the minor Cu enrichment that occurs is not associated with Au.
2.Hydrothermal vein, breccia, and/or replacement ore styles, characteristically in specific structural sitesTick Hill meets this characteristic
3.Abundant magnetite and/or hematite Tick Hill has abundant early magnetite overprinted by hematite
4.Fe oxides with Fe/Ti > those in most igneous rocks and bulk crust Tick Hill meets this characteristic
5.No clear spatial associations with igneous intrusions as, for example, displayed by porphyry and skarn ore deposits Gold is largely hosted in ~1775Ma quartz-feldspar mylonite, interpreted as leucogranite. If Au was introduced then, it would have formed in association with the Tick Hill intrusive suite. If gold pre-dated D1, then relationships with intrusive rocks are not clear.
6.Broad space-time association with batholitic granitoids This depends on main stage of mineralisation is interpreted. The late D3 fluid alteration stage dated at 1525 Ma coincides with the emplacement of the Williams-Naraku Batholith. But it is not clear if the gold was introduced during that stage. Gold is largely hosted in ~1775Ma quartz-feldspar mylonite, interpreted as leucogranite. If Au was introduced then, it would have formed in association with the Tick Hill intrusive suite.
7.In settings with pervasive alkali (Na) metasomatism Tick Hill meets this characteristic
8.Late-stage carbonates are common Tick Hill meets this characteristic
9.Typically enriched in minor elements including: F, P, Co, Ni, As, Mo, Ag, Ba, LREE, U Tick Hill does not meet this characteristic. Instead gold is
largely pure, with high-grade zones showing a correlation with minor Ag, Bi, Pd and Pt.
10. Depth of formation 1-10km Probably, but dependent on when gold actually formed. During D3, when Au was mobile, conditions were within this range.
11.Widespread pre-sulphide, Na and NaCa alteration (albite) predates more proximal K-Fe alteration (sericitechlorite) and mineralization Tick Hill meets this characteristic, but again there is the issue of when gold was actually introduced into the system
12. Mineralizing fluids are complex brines, commonly with a carbonic component The fluids during D3 were H2O-rich brines with no carbonic
component.
13.Brines may come from magma directly or indirectly, or could be derived from basinal/metamorphic fluids Who knows, Oxygen isotope studies are inconclusive
14. Possible mixing of S-poor, metal-rich brines with S-bearing fluids at site of deposition Possible
15.Tectonic setting uncertain, but possibly anorogenic and linked to underplating Who knows. The rocks appear to have experienced a clockwise P-T path with significant exhumation following D1 events. During D3 red rock alteration, the rocks appear to have been in extension.
 Considering these criteria, and acknowledging the wide range of characteristics that occur
in IOCG deposits in the Mt Isa block, we suggest that Tick Hill does not represent a IOCG deposit.
 During D3, Tick Hill was overprinted by the same fluids that occur throughout the Eastern Fold Belt in the Mt Isa Block, and that have been linked to IOCG’s (e.g. Williams et al. 2005). Therefore, Tick Hill shares many characteristics with IOCG’s especially with respect the alteration characteristics. However, the gold probably predates this D3 alteration stage.
 Considering that: at least some Au is early; occurs in association with little else but Bi; selenides are common; the host rocks may be as old as >1850 Ma; and host lithologies were repeatedly affected by deformation, metamorphic and metasomatic overprints, we suggest that the Tick Hill deposit retains many characteristics of the Au-Bi-Se rich, oxidized end-member type for ~1850 Ma ironstone-associated Au-Cu-Bi deposits in the
Tennant Creek Gold field (e.g. Skirrow & Walshe, 2002).

7. Exploration implications

We note:

 D1 shear-hosted Au models and D3 late Au models have not resulted in exploration success in the past.
 Almost all major gold occurrences around the globe occur in association with other gold occurrences. The Tick Hill situation is highly anomalous in this regard.
We suggest:
 Considering the fact that the volcano-sedimentary host lithologies to gold at Tick Hill, which were previously interpreted as Corella Formation, are likely to be much older and could be part of the Leichhardt volcanics. This means that the volcano-sedimentary sequences in the Kalkadoon-Leichhardt domain could be prospective for gold.
 Considering that gold may have formed early, and did not get introduced during the pervasive fluid events that dominate the alteration assemblages in the pit (i.e. the chloriteepidote-actinolite-carbonate alteration), but instead was introduced with the earlier alteration assemblage of silica-magnetite-hornblende; and considering that Bi and Se may represent localised remnants of an earlier alteration/mineralisation event as well, than exploration should focus on Mt-qtz alteration with elevated Bi-Se rather than typical IOCG style alteration/mineralisation.
 The D3 deformation structures determine the current, local geometry of the orebody, but they may have been unrelated to deformation patterns at the time of gold formation (i.e. this observation follows the syn-D1 models that guided exploration in the early days)"





*All bold type has been added by me.