Chatham Rock Phosphate Limited · NZX:CRP
Chatham Rock Phosphate — 26th IAGS Conference, Rotorua 2013
26 slides from Chatham Rock Phosphate's conference presentation, 2013
Slide 1: New Insights into the Origin and Distribution of Phosphate Deposits on the Chatham Rise
New Insights into the Origin and Distribution of Phosphate Deposits on the Chatham Rise Simon HH Nielsen Kenex, Ltd. 26th IAGS Conference, Rotorua, New Zealand
Slide 2: Outline
Outline • Chatham Rise geology and paleoceanography • Deposit characteristics: • Nodule shape and texture • Geochemistry • Conclusions • Are there signs of multiple phosphatisation events on the Rise?
Slide 3: World Class Phosphate
World Class Phosphate Phosphate known from samples on the Chatham Rise since 1952 Chatham Rock Phosphate holds an exploration license over part of the Rise, has applied for a mining license Kenex is involved in application processing, database management, surveying and Mullich & Rasch 1985 prospecti
Slide 4: Tectonic Setting
Tectonic Setting Laird & Bradshaw 2004 • Coherent structural high extending 1100 km east from the South Island. • Formed through Late Cretaceous rifting from Gondwana, as a volcanic arc. • The Chatham Peninsula persisted through the Paleocene, followed by limestone deposition in the central and east
Slide 5: Geology
Geology • Cretaceous faulted basement and fault basin fill, followed by hiatus • Late Eocene cherty marl/limestone– Early Oligocene soft to firm nannofossil chalk, followed by hiatus • Mid-Miocene limestone and hardground, phosphatised to nodular gravel in Late Miocene as lag deposit on firm to hard
Slide 6: Oceanographic Setting
Oceanographic Setting Modern Subtropical Front on southern flank of Chatham Rise. O2 minimum zone associated with Upper Circumpolar Deep Water Important feature in S. Pacific paleoceanography. Deep coring mostly on flanks and in adjacent basins (crest = condensed section). Hayward et al 2004
Slide 7: Sampling efforts
Sampling efforts Surveys in the 60s (Global Marine/JBL), 1978 (Valdivia) and 1981 (Sonne) Methods include high- resolution seismics and shallow-penetration sampling.
Slide 8: Sample distribution
)_Samples \VA_Samples |” JBL_Sample SO_Sam ° ° . Legend Creating opportunities in the spatial world Sample distribution
Slide 9: CRP 2011/2012 Surveys
CRP 2011/2012 Surveys • 4 surveys from Dec 2011 – April 2012 • > 200 samples using grabs, box corers and vibro coring. • > 1100 km2 of multibeam bathymetry • > 100 km of ROV transects
Slide 10: CRP 2011/2012 Surveys
CRP 2011/2012 Surveys Irregular seabed, with (glacial) scours and pits 50 large grab samples (500 – 2000 kg / sample) 43 ROV transects for environmental studies
Slide 11: Seafloor Characteristics
Seafloor Characteristics • Soupy glauconitic sandy mud over lag layer of phophatised hardground nodules • Substrate is a stiff, intensely bioturbated pelagic chalk. Pedley and Bennett, 1985
Slide 12: Sampling method
Sampling method
Slide 13: Large samples, large efforts
Large samples, large efforts Onboard sample processing, R/V Sonne 1981 Fines were thrown back. Von Rad & Rösch 1984 Onshore sample processing, 2012 Fines were kept, if washed with freshwater
Slide 14: Multiple Events? Nodule Shape
Multiple Events? Nodule Shape • Older hardgrounds may have undergone more Miocene Miocene intensive alteration leading to Eocene Pleistocene smoother texture and rounder shape • Samples mainly Oligocene Eocene from Oligocene seismic facies… Oligocene Miocene Seismic facies (Falconer et al. 1984)
Slide 15: Nodule Shape - Middle of Crest
Nodule Shape - Middle of Crest Round/smooth = most intense alteration Irregular/rough = less alteration Rounded, smooth nodules Most ‘mature’ deposit?
Slide 16: Nodule Shape - Eastern Area
Nodule Shape - Eastern Area Pitted nodules, obvious bores/burrows Partially phosphatised and less altered hardground Less mature deposit?
Slide 17: Nodule Shape - Southern area
Nodule Shape - Southern area Irregular nodules, obvious bores/burrows. Less mature deposit?
Slide 18: Nodule Shape - Northern Area
Nodule Shape - Northern Area Irregular nodules, pitting, bores, and burrows. Less mature deposit?
Slide 19: Intensity of Phosphatisation
Intensity of Phosphatisation 116 samples with XRF geochemistry (out of > 1400) Tendency for low (and highest?) P points to Bulk (XRF) geochemistry, > 8 mm fall on the periphery
Slide 20: Geochemical Populations
Geochemical Populations 2.5 1 1.4 0.9 1.2 2 0.8 0.7 1 1.5 0.6 Al2O3 % 0.8 Na2O % K2O % 0.5 1 0.4 0.6 0.3 0.4 0.5 0.2 0.1 0.2 0 0 0 0 2 4 6 8 10 0 2 4 6 8 40 45 50 55 SiO2 % Fe2O3 % CaO % Bulk (XRF) geochemistry, > 8 mm fraction Signs of 2 populations of phosphate nodule geochemistry High Al + K = gl
Slide 21: Geochem. Population Distribution
Geochem. Population Distribution DD and Ti samples are from the western (northern) region, and generally in Oligocene sediment facies. So and Va samples are from the south and east, and often in younger (Miocene) sediment facies.
Slide 22: Oligocene vs. Miocene Nodules
Oligocene vs. Miocene Nodules 2.5 1 1.4 0.9 1.2 2 0.8 0.7 1 1.5 0.6 0.8 Al2O3 % Na2O % K2O % 0.5 1 0.4 0.6 0.3 0.4 0.5 0.2 0.2 0.1 0 0 0 0 2 4 6 8 10 0 2 4 6 8 40 45 50 55 SiO2 % Fe2O3 % CaO % Are the Miocene samples (red points) less ‘mature’?
Slide 23: Will the nodules tell the story?
Will the nodules tell the story? Glauconite Fe hydroxide Phosphate Phosphatisation progressed inwards from the outside. Can detailed analysis of nodules show multiple phases of alteration? (backscatter, scanning XRF) Samples from a wider area wanted!
Slide 24: Conclusions
Conclusions • Chatham Rise is covered by cool-water pelagic carbonate, hardground rubble and unconsolidated sandy mud. Sediment ages and hiati tie in with onshore geology (multiple Marshall Paraconf. equivalents?) • Hardground formation associated with influx of cool bottom water from Antarctic/Sout
Slide 25: Thanks to Collaborators at…
Thanks to Collaborators at… Boskalis, Chatham Rock Phosphate, GNS Science, Kenex Ltd, NIWA, Odyssey Marine Exploration
Slide 26: Kenex contact details
PO Box 41136, Wellington, New Zealand W: www.kenex.co.nz E: info@kenex.co.nz
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