Interpretation of Multi-Element Geochemistry

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1 Interpretation of Multi-Element Geochemistry Gregg Morrison & Terra Search Project Team December 2017

2 Metallogenic classification using ME data A lot of 46 element ICP data resides in company files with limited interpretation IOGAS and Leapfrog have helped substantially but more for rock type definition than metal zoning We have developed methodology for classifying deposit types geochemically and for deposit metal zoning using the augmented Explorer 3 database. CLASSIFICATION METHODOLOGY Based on 13 metal set Au Ag As Sb Pb Zn Cu Bi Te Mo W Sn Select metals & sort (use Clark to eliminate BLD values) Define populations by rock type or favoured metal and calculate an average Select background type e.g. granite from Levinson table and normalise the population. List relative enrichment in orders of magnitude Compare with reference chart to define system type Scheme based on ~100 examples from Charters Towers region

3 Typical dataset rock chip, n=238, no data Ba Sn W average granod enrich Ag As Au Ba Bi Cu Mo Pb Sb Sn Te W Zn Au Ag Pb Bi(As Cu) +/-Te Zn Table of averages for each element divided by values for typical granodiorite to get enrichment. Elements listed in bold represent the relative order of enrichment for this suite. Au with Ag Pb Bi indicates a magmatic system with moderate fractionation. Strong fractionation would have richer base metals. Bi +/- Te rich suggests an intermediate intrusive source like tonalite-granodiorite Ag-Pb-As imply distal zone is being sampled at surface. Overall this sample suite could represent a mafic magmatic hydrothermal system emplaced at porphyry level. This is consistent with known geology & presence of euhedral buck quartz veins and granitic vein dikes.

4 CT ME geochem: Classification using multi-metal data Porphyry level IRGS have AU PM BI TE (polymetallic ) Bi dominant in felsic and Te dominant in mafic intrusive systems Plutonic Cu has Cu-Mo-Bi +/- peripheral As Pb Zn Orogenic Gold have Au-basemetals +/- As Te (no Bi) Epithermals tend to be Au-As dominated Element Class Deposit Type Core Age Example AU PM BI felsic IRGS Mo-W-Bi CARB-PERM Mt Wright AU PM BI TE intermediate IRGS Cu-Mo CARB-PERM Mt Leyshon AU PM TE BI int-mafic IRGS Cu-Mo, Cu-Au CARB-PERM Mt Remarkable AU AS BI TE+/-BM mafic porphyry IRGS Cu-Au LCARB, DEV? Ravenswood AU AS TE BI mafic plutonic IRGS? Au? CARB, DEV? Mt Clearview CU MO plutonic IRCS Cu-Mo, Mo SIL Titov AU BM +/- AS, TE orogenic intrusion hosted EDEV Charters Towers AU +/- TE AS BM epithermal ECARB, PERM Pajingo AS=As+/-Sb; AU=Au+/-Ag; BM=Cu+Zn+Pb; PM= Cu+Pb+Zn+As+/-Sb

5 KIDSTON ME GEOCHEM INTERPRETATION Au correlates best with basemetals (Pb, Zn) whereas the enrichment suite has high As overall. The Pb-Zn association is also more favourable metallurgically element suite from minerals enrichment in grab samples Enrich DDH n= el only correlation Au Ag Zn Cu Pb Mo Bi F Te Au Bi Ag Zn Pb Te As Mo Au As Ag Cu Zn Pb Au Pb Zn As AU AG CU PB ZN AS MO Mine Ex AU 1 late AG Au Pb Zn As CU Ag Cu Pb PB Pb Zn As ZN AS MO

6 KIDSTON Pipe Metal Zoning Confined in pipe Overall zoning on a Thermal gradient Au only above sill With Pb-Zn-Cu Deep Mo-W-Bi Classify: IAMX Exposed distal BM Core Mo-W- Bi

7 CT ME geochem: metal zoning model For detailed zoning do Z-score & PCA analysis & IOGAS / Leapfrog display on assemblages of metals in thematic map or cross-section or 3D. With two or three dimensional data sets and a few hundred data points It is possible to build a metal zoning model Do Z-score(standard deviation) test on each element to make all elements equal Plot the Z-scores in plan or section and manually look for spatial overlap of metal concentrations Combine and average Z-scores for multiple elements to define zones Or do a principal component analysis on the Z-scores to define element clusters Contour zones

8 Ravenswood District: Three Sisters metal zoning Mo-W in rhyolite breccia whereas Au is related to andesite dikes and underlying diorite

9 IRGS NQ Mt Wright soil and rock metal zoning Zn-Ag-Pb Pb-Zn 3km diameter soil anomaly Zn, Bi, Au only 5ppb on hill 1km tall system, well zoned Au 0.1ppm at surface, Best Au ore m below

10 3 element Z-score wireframe Mt Wright Pb-Zn-Ag (0.1 Au) Zn-Ag-Au(lo grade) Au Bi Cu (ore) inner Au-Cu (ore)

11 Igneous-metal classification of porphyry hydrothermal systems CLASSIFICATION & ZONING PATTERNS FOR PORPHYRY-RELATED HYDROTHERMAL SYSTEMS METAL ASSOCIATION CLASSIFICATION Au Cu-Au Cu-Mo Mo-W-Bi Sn-W Sn-B EXAMPLE Eastern Australia Fifield Goonumbla Mount Leyshon Kidston Herberton Cooktown EXAMPLE World Maricunga Chile British Columbia Bingham Climax Erzgebirge NE Tasmania IGNEOUS CHARACTERISTICS CHEMICAL TYPE; FRACTIONATION; REDOX M, U-F, O M, U-F, SO-O I, U-F, O I, F, O-R I, F, R S, F, R IGNEOUS ROCK TYPE ON QAP DI-QD-TN DI-MZD-MZ-QMZ DI-GD-MZG QMZ-MZG-SYG MZG-SYG-AFG SYG-QSY-ASY METAL ZONING MARGINAL DISTAL (As) DISTAL (BM) PROXIMAL (BM) CORE Hg, S Ca Ca F, U F, Ba, Se, Hg, U F As (Au) Au As Sb (As, Sb, Au) (As Ag Sb Au) As (Au) As Pb, Zn, Ag, Sb, (Au) Pb Zn Ag Au (Cu Mo Te) Pb Zn Ag (Au, Bi) Zn Cu Pb Bi Au Pb Ag Zn Zn Pb Ag Au Cu Mo (Ag, As) Cu (Zn) Cu Au Ag (Bi Te) Cu (Au Bi Te) Cu Mo Bi Cu Bi Mo (W) Au, Te, (Pt) Cu Au (Te) Cu Mo W Mo Bi Sn W Sn B (W) Klondike Exploration: AMIRA P425, July 1997 Combining the igneous classification and the zoning pattern we can work back and forth between when there is limited information. With multi-element data we can interpret the most likely position in system based on the most enriched elements relative to background. And define the system type based on key elements like Te, Bi, Mo, Sn N.B. different position for Au concentration(shaded) distal/felsic

12 MM data interpretation: Metal Zoning in IRGS model Overall metal association distinguishes crustal levels of systems As-Sb typical epithermal Basemetals typical porphyry level Bi-Te without basemetals plutonic

Interpretation of Multi Element Geochemistry in the Charters Towers Region

Interpretation of Multi Element Geochemistry in the Charters Towers Region Gregg Morrison & Simon Beams & Terra Search Project Team CT MM geochem: Introduction Terra Search/GSQ Explorer 3 database is a