conceptual exploration for tin, gold and diamond placers in … ·  · 2015-04-09by understanding...

Conceptual Exploration for Tin, Gold and Diamond Placers in

‘Sundaland’ (Indonesia & Malaysia) by Understanding the Late Cainozoic

Stratigraphic Context

18-21 March 2015 PACRIM, Hong Kong, China

Daud Batchelor

PhD MSc MEngSc FAusIMM CP

Daud Batchelor & Associates Pty Ltd 1

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

• Outline of theTalk – Regional setting, climate & sea level changes,

geological evolution & Late Cainozoic stratigraphy

– Tin, gold & diamond placer fields: stratigraphic-placer association & evolution through time

– Regional Stratigraphic Correlation

– Concluding Remarks re: conceptual placer exploration

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

• Introduction – Giant placers formed in SE Asia due to favorable

mineralisation source types, tropical climate & Quaternary climatic/sea level changes; mined >1000 yrs

– World’s most productive tin province is Sundaland (Indonesia, Malaysia, Thailand, Myanmar); mainly placers

– Kalimantan before 1860s was major diamond producer (Martapura in S Kalimantan; Landak in W Borneo).

– In 1980s gold rush erupted in Borneo, Sumatra, Java, Sulawesi and Peninsular Malaysia; continues today

– Knowing genesis of rich placers, their association with specific palaeoenvironmental episodes & stratigraphic units facilitates their exploration and discovery.

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

PLIOCENE

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

• Quaternary climate and sea level changes – Low sea level (glacial) periods : cooler seas,

seasonal continental climate; drier as less sea evaporation; less rainforest more grassland; landscape planation & soil fmn. Higher sea level (interglacial) periods : warmer seas, insular tropical climate; high evaporation/rainfall, stronger vegetative growth enhances linear valley stream incision

– Similar response in placer genesis of 3 mineral types due to similar landscape evolution following Mid-Miocene high sea levels.

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

Model for piedmont fan and alluvial braidplain deposition of Old Alluvium (west Malaysia-Indonesia) and Upper Dahor

Formation (Kalimantan, Indonesia)

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

PT Timah bucket-ladder dredge KK Kundur, off Kundur Is near Singapore; maximum digging capability for buried Sundaland river

channel deposits to 50 metres below sea level

Conceptual exploration model for offshore placers in the Sundaland Tin Province, using their geomorphic setting & stratigraphic association

(modified from Sutedjo, 1974 and Aleva, 1973)

MICROMINE Mining & Geological Software: Seam Correlation , Placer Tin, Bangka Island, Indonesia

Metres

Grade

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

• KALI MAS INTAN = kali (rivers) mas (of gold and) intan (diamonds)

• Best studied deposits geologically are Cembaga Buang (Sampit R.), Ampalit (Katingan R.) and PT Mercu Buana (Kahayan R.) gold deposits & diamond placers of Martapura area (S Kalimantan), located in drainages flowing into the Java Sea.

• Important regional stratigraphic unit is the Dahor Formation – comprising Lower Dahor Fmn (dark clays; Miocene-Pliocene) and Pleistocene Upper Dahor Fmn (typically arenacous).

• Important primary gold mineralisation sources in Central Kalimantan Belt are Miocene volcanic rocks.

Gold and diamond placers in West, Central and South Kalimantan, Indonesia

(After Witts et al, 2012)

Schematic cross-section showing stratigraphic relationships in Cempaga Buang gold placer deposit,

Central Kalimantan, Indonesia

1. 2. 3.

4. 5.

Interpreted Stratigraphic Subdivision, Offshore Southeast Kalimantan (amended from Ringis, 1996)

Offshore Onshore (SE Kalimantan)

Dep

th b

elow

Sea

Lev

el (

m)

10.0

20.0

40.0

60.0

CHY CHO

CHO

CHO

CHO

CHY

CHY CHY

MA

FS

FA FA

FS MA

WT WT

WT

MS

MS

Weathered Tertiary WT CHO Older Channel Targets CHY Younger Channel Targets

FA Alluvial Plain

FS Alluvial Fan Young Alluvium

Marine Blanket MA

MS

LEGEND

Late Cenozoic Provisional Correlation of Kalimantan Sequences with Malaysian-Indonesian Tinfields

d

d d d

d

u u

u

d d d d

d

d d

d u u u

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

• Cassiterite (SG:7; brittle, crystals equant) concentrations more restricted to Old Alluvium and Transitional Unit; relatively limited transport from 1° sources.

• Gold (SG: 15-19; but platey) concentrations may occur equally in Old Alluvium and Young Alluvium; often contain important supergene component.

• Diamond (SG: 3.5), a lighter HM, easily mobilised, reworked and transported; consequently richest in younger alluvium in Martapura field.

• Conceptual exploration successful by understanding HM associations with Sundaland stratigraphic units - essential in challenging search for offshore & deeply buried placers

• Exciting future in new frontiers (Tin - Myanmar, West Kalimantan, deeper marine areas; Gold – offshore south Java; Diamonds – offshore SE Kalimantan).

Concluding Remarks

Exploration for Tin, Gold, & Diamond Placers using Late Cenozoic Stratigraphy in Sundaland, SE Asia

Thank You