The Carson-Hart Large Igneous Province intrusive complex:

implications for Speewah-style V-Ti-Fe mineralisation in the Kimberley

Karin Orth

University of Tasmania

LIPs • Large Igneous Provinces (LIPs) represent the largest

known volcanic episodes on Earth – each lava flow representing 100s-1000s km3 of magma with most erupting over a relatively short time span (1 -5 my).

• The largest ancient examples: Siberian Traps, the Karoo, Parana and Deccan, are considered important Earth events with debated influence on the evolution of the planet and life on Earth. Amongst the best studied examples is Columbia River Flood Basalts.

Geology

Carson-Hart LIP

• Hart Dolerite is the intrusive portion of the Carson-Hart LIP.

• It intrudes the Speewah and Kimberley Basin.

• Estimated to lie 2-3 km beneath the eruptive surface

0

50000

100000

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ColumbiaR

HLIP CarsonVolcanics

HartDolerite

km3

• In terms of LIPs the Carson-Hart LIP is about the same size as the Columbia River Flood Basalt Province of the western USA

• An order of magnitude smaller than the other flood basalt provinces, such as the Siberian Traps, Karoo, Parana and Deccan

• Hart Dolerite forms 83% of whole LIP

Volume Estimates

0

1000000

2000000

3000000

4000000

5000000

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8000000

9000000

Deccan Columbia R HLIP

km3

17%

83%

Carson Volcanics Hart Dolerite

Carson-Hart LIP

Geochronology

Geochronology

Geochronology

Two dates SHRIMP U–Pb ages from zircon and baddelyite in more felsic portions (granophyre): 1799±17 and 1795 ± 15 Ma with a final weighted mean age of 1797 ± 11 Ma for the age of igneous crystallization.

Sheppard et al 2012

Outcrop characteristics 100s of kilometres along strike continuity of units within the sill Here the dolerite form hills which are collapsing and so do not support much vegetation Recessive area here is monzogranite which is called granophyre

DAM01 Yampi Peninsula

Outcrop characteristics • Dolerite can also form black soil plain, which

form excellent grassland but little outcrop

YUR27

Millie Windie area

Sill Architecture

Sill Architecture

5 km

Sill Architecture

Inclusion-rich, high magnetic susceptibility readings

Sill Architecture

Sill Architecture

Pegmatitic segregation common near the top of the upper sill

Lennard River 1:250 000 Aeromagnetics-RTP colour-2008

Sill Architecture

Sill Architecture

Speewah Dome

V-Ti-Fe resource Measured Resource 322 million tonnes @ 0.32% V2O5 and 2% Ti

(from King River Copper Ltd website)

Speewah Dome

modified from Eves 2010

Red Hill Buckman

Central

(Speewah Metals)

Disseminated Magnetite Gabbro

Downhole geochemistry plots of some major oxides (wt%) and trace elements (ppm) for SDH09-01. Note high V near the base of the magnetite gabbro.

EOH at 581.8 m

Summary of the HyLogger data provided by L. Hancock

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0 2 4

TiO2

10 15 20

FeO*

0.00 0.50 1.00

P2O5

0 500 1000

V

0 50 100

Mg#

0 50 100

Rb

Elevated V in the geochemistry database in the Hart Dolerite around Millie Windie. Samples with V>400 ppm

V= 849 ppm

V= 1545 ppm

V=484 ppm

V = 1773 ppm in a sample from Hope Creek which is north of Mt Hart near the Yampi Peninsula

10 km

Conclusions • The 1.79 Ga Carson-Hart LIP is comparable to smaller volume LIPS, such as

the Columbia River Flood Basalts in volume • 83% of the Carson-Hart LIP comprises intrusive rocks (Hart Dolerite) • Four main units comprise the Hart Dolerite sill architecture in the Millie

Windie valley lower complex • The sill achitecture can be consistent over strike lengths of 100s of

kilometres • V-Ti-Fe resource at Speewah Dome is hosted in the base of an iron-rich

gabbro, which appears to be present in other areas along the southern margin of the Kimberley Basin

• Increased prospectivity of the Hart Dolerite for this style of mineralisation across the Kimberley