the carson-hart large igneous province intrusive complex ...• large igneous provinces (lips)...
TRANSCRIPT
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The Carson-Hart Large Igneous Province intrusive complex:
implications for Speewah-style V-Ti-Fe mineralisation in the Kimberley
Karin Orth
University of Tasmania
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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.
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Geology
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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
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0
50000
100000
150000
200000
250000
300000
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
6000000
7000000
8000000
9000000
Deccan Columbia R HLIP
km3
17%
83%
Carson Volcanics Hart Dolerite
Carson-Hart LIP
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Geochronology
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Geochronology
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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
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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
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Outcrop characteristics • Dolerite can also form black soil plain, which
form excellent grassland but little outcrop
YUR27
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Millie Windie area
Sill Architecture
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Sill Architecture
5 km
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Sill Architecture
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Inclusion-rich, high magnetic susceptibility readings
Sill Architecture
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Sill Architecture
Pegmatitic segregation common near the top of the upper sill
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Lennard River 1:250 000 Aeromagnetics-RTP colour-2008
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Sill Architecture
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Sill Architecture
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Speewah Dome
V-Ti-Fe resource Measured Resource 322 million tonnes @ 0.32% V2O5 and 2% Ti
(from King River Copper Ltd website)
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Speewah Dome
modified from Eves 2010
Red Hill Buckman
Central
(Speewah Metals)
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Disseminated Magnetite Gabbro
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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
200
400
600
800
1000
1200
1400
1600
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
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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
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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