JON HRONSKY UNCOVER MINERAL SYSTEMS WORKSHOP 2 JULY 2013 The WMS Approach to Predictive Targeting using the Mineral System Method: A Dynamic, Fluid-Centric Approach 1

Basic Physics of Ore Formation 2 Diffuse Metal Source Region Concentrated Metal Deposit Advective Fluid flux (= Energy Flow) Fluid Sink

3 Ore specimen- centric Host Rock - centric Structure-centric Fluid Flux-centric Early 1900s 21 st Century Increasing Scale of Observation

A Key New Concept: Ore-formation as a Self-Organized Critical System 4 Fluid (Energy) Source Fluid Reservoir Fluid Sink Transient Exit Conduit Threshold Barrier (need not be a physical seal) Thermal halo - produced by entropy dumped into environment Episodic focused energy and mass flux Slow persistent fluid flux

5 Electric Charges Accumulate Slowly Threshold Barrier: Resistive Air Ground Transient Rapid Breach of Threshold Barrier The Lightning Analogy for Ore-Forming Systems

6 Electric Charges Accumulate Slowly Threshold Barrier: Resistive Air Ground Transient Rapid Breach of Threshold Barrier The Lightning Analogy for Ore-Forming Systems

7 Regional Scale Camp Scale Deposit Scale Mineral System Framework 1: Ore Genesis as the Focus of a Scale-Hierarchical Fluid-Driven Mass-Concentrative System Critical Geochemical Elements can be mapped to this Physics –based framework

Fertility Proximity to Lithosphere-scale Structure Favourable (Transient) Geodynamics Ore Genesis Mineral System Framework 2: Ore Genesis as the Conjunction of Three Independent Sets of Favourable Conditions 8 + Preservation = Target

Physics of Ore Formation Means Only Certain, Rare Geodynamic Environments have Ore-Forming Potential 9 ACTIVE FLUID PRODUCTION NON-DILATIONAL (ie. “TIGHT”) GEODYNAMIC SETTING Fluid-flux driven by fluid pressure not tectonic strain – Fluids organise in this space ORE FORMATION POTENTIAL

Transient Compression: Tampakan District, Mindanao Red area = amount of convergence partitioned into intra-plate shortening during subduction reversal. From Rohrlach (2002) 10

11 Chiodini et al. (2004) Extensional Zone: Diffuse Fluid Flow Compressional Belt: Organised Fluid Flow

12 Application of Mineral Systems Framework 2: Carlin Gold Province Example

13 Schematic Section - Continental Crust (Cawood et al, 2013) Base of Gold Depositional Window- Porphyry Style deposits Base of Gold Depositional Window- Orogenic Gold deposits (more CO 2 -rich fluids in retro-arc positions)

Metallogenic Association Typical Deposit Types Emplacement EnvironmentLong Term Preservational Potential 1 Porphyry-suite deposits Topographical positive Constructional Arcs Low – typically very high denudation rates (up to 1km per Ma) 2 Rift associated Epithermal, VMS Topographically negative Rifted Arcs; shallow rifts for Epithermal, deep submarine rifts for VMS Low for Epithermals in shallow rifts; Moderate for VMS in deeper rifts (syn- cycle reworking and erosional possible) 3 Orogenic AuInverted Pericontinental Rift zones right at cratonisation High – late orogenic timing means limited syn-cycle erosion, particularly in hot orogens 4 Olympic Dam style IOCG Sleeper style Epithermal Intracontinental rifts or anorogenic sites High if emplaced post-cratonisation Moderate if emplaced during the orogenic cycle 14 Summary of the Preservational Potential of Major Au(Cu) deposit types that form in Accretionary Orogens Metallogenic Association framework derived from Hronsky et al (2012); Note that all deposits are susceptible to removal by subsequent unrelated orogenic cycles

15 Example of integrating both Mineral System Frameworks to define a generic targeting model for a particular ore deposit type (Note -Targeting Elements related to these Constitutive Elements depend on local geological environment; at the province-scale we will also need to consider preservation) Association 1 (Porphyry Cu Deposits)

Critical Element: High-level component of the Mineral Systems Frameworkl Constitutive Element: Generic geological manifestation of a critical element for deposit type of interest Targeting Element: Specific geological manifestation of a constitutive element in the area of interest Mappable Element: Feature that can be directly observed in available data and which is a proxy for a targeting element (eg magnetic anomaly) Modified from McCuaig et al (2010) Framework for Translating a Conceptual Targeting Model into Useful Proxies Our generic knowledge about a particular ore type Our local knowledge about a region The way we chose to organise our thinking