EGU Gift workshop

Role of Organic Matter in Mineral Deposits Two case studies

Kliti Grice Deposition of Organic Matter

Erosion

Organic Matter

River Run-off

Anoxia Sedimentation Deposition Ground Rock

Extraction with organic solvents

rock

EXTRACT- looks like oil

Liquid Chromatography

Saturate Aromatic Polar hydrocarbons hydrocarbons hydrocarbons Special mass spectrometry techniques to identify hydrocarbons/biomarkers and to determine 13C/12C of hydrocarbons Macrofossils & Molecular (biomarkers) Biochemical Erytrops

OH OH

OH OH

DINOSAUR SKELETON Molecular Skeleton (Biomarker)

Stages of Formation

• Diagenesis

TYPE III • Catagenesis

TYPE II • Metagenesis

HUNT, J.M. 1996. Petroleum and Geology. EXPRESSION OF STABLE ISOTOPE COMPOSITION

 d in ‰ (per mil) = (R sample - R standard) X 1000 (R standard)

R is the measured ratio of heavy to light isotope as determined from an isotope ratio mass spectrometer e.g. 13C/12C, relative to an international standard.

Stable Isotopes -100 Methane

-80

13 Chromatiacea d C- 60 ‰ -40

-20

0 CO2 carbonate In 2012 20

Habitat of Chlorobi PZE cf. Present Day Black Sea Microbial Mats (Shark Bay)

O 280Cyanobacteria million year old 2 hv KupferschieferCO2 + H2O (Copper CHO + energyShale, Germany) 1.6 Billion year old (Lead, Zinc, Silver Deposit, Australia) H S e.g. Grice et al., Science 2005; Brocks et al., Science 20052 bacteriochlorophylls 3 majorChlorobi extinction events isorenieratene hv H2S + CO2 CHO + S + energy

H2S H2S

2- SO4 Sulfate reducers Chlorobi Biomarkers PZE

pigment Biomarker Isorenieratane

Grice et al., 1996

Magnesium HO

Vanadium, N N M g Copper, N N Iron & Zinc- R 2

O Metal transport? O O Farnesyl

O HN O

Methyl Iso -Butyl maleimide Grice et al., 1995 Radiolytic alteration of biopolymers in the Mulga Rock Uranium deposit

Caroline Jaraula, Lorenz Schwark, Xavier Moreau, Kliti Grice, Walter Pickel, & Leon Bagas CSIRO Minerals Down under Flagship Organic Geochemistry of Mineral Systems Study Area

Narnoo Basin Stratigraphy

Mulga Rock

Energy and Minerals Australia, Ltd Objective

1.Recognize biological sources of molecular markers.

2.Identify relationships between molecular markers and uranium accumulation.

3.Detect radiolytic effects on molecular marker composition. Ambassador Prospect drill core 5766

kaolinite Ground samples Dichloromethane Sonication extraction Methods Bitumen

Silica gel Liquid Chromatography Fractions

Aromatic aliphatic Polars hydrocarbons hydrocarbons KOH-treated silica gel Liquid Chromatography GC-MS

acids GC-IRMS ketones alcohols δ13C GC-MS

GC-IRMS δ13C Kerogen source and maturity

Effect of ionizing radiation: Decrease in H/C, HI or dehydrogenation (e.g. Landais et al., 1987; Pierce et al., 1958; Zumberge et al., 1978; Křibek, 1991; Landais, 1993)

Legend U concentration < 2000 ppm U concentration > 2000 ppm Total S correlation with [U]

3

2 (%)

y = 0.0005x + 0.6147 Total S S Total 1 R² = 0.9239

0 - 1,000 2,000 3,000 4,000 5,000 6,000

U (ppm) Depositional Environment

MR 49

3

2 Total S (%) S Total 1 y = 0.0586x + 0.2029 R² = 0.9341 Freshwater* 0 0 6 12 18 24 Total organic carbon (%) complex shallow depositional systems ranging from lacustrine to deltaic, swampy wetland and even shallow lake (Douglas et al., 2011)

* Berner RA, Raisewell R, 1984 - C/S method Localised uranium enrichment

1 - pollen 2 – spores 3 - woody material The predicament in Mulga Rock: rare occurrence of discrete mineral or crystal phases hosting uranium as uraninite [UO2] and coffinite [U(SiO4)1-x(OH)4x] (Energy & Minerals Australia, Pty Ltd, ) Aliphatic fraction

-26.7 -29.0 -27.1 -29.1

-28.5 -29.6

-29.1 -29.4

-29.8 -28.8

-28.8 -28.4

δ13C (‰, VPDB): average of n-C25 to n-C29; average of n-C17 to n-C22 ; Aliphatic fraction

Δ= +0.4 Δ= -0.1

Δ= -0.6 Δ= +0.2

Δ= +1.4 Δ= 0.0

δ13C (‰, VPDB): 13 13 average of n-C25 to n-C29; average of n-C17 to n-C22 ; Δ= δ C25 to 29 - δ C17 to 22 Links between uranium and organics

Lines of evidence Organic matter source/type

δ13C -26.7 (‰, VPDB) -27.1

IMPLICATIONS: 1. Highly aliphatic biopolymers are closely associated with uranium:

2. Provide a chemical trap for uranium Mechanism

Aliphatic components Indicators & mechanism X Thermal cracking Δ= +0.4 X Change in Temperature regime/ burial history X Microbial source No isoprenoidal components X Microbial degradation No UCM Δ= +0.2 Radiolytic cracking

Δ= 0.0 Alkanone distribution

Summed fragmentograms m/z 58+72+86+100 n-pentacosanone isomers

Increase in [U] & S% n-alkan-2-one relative abundance Radiolytic alkanone formation Conclusions & Implications

• Radiolytic cracking of aliphatic biopolymers in Ambassador deposits • pollen and spores as possible sources of highly aliphatic biopolymers are recalcitrant & likely have a close spatial relationship with U, perhaps serving as a chemical trap. • Radiolysis and the cascade of secondary and tertiary reactions (i.e. cracking, radioysis of water to produce OH- radicals, cabonylation) produced the suite of alkanones • Low pH and high S inhibit alkene isomerization such that alkan-2-ones become the predominant isomer in samples with high U and S contents. • Identification of radiolytic molecular markers provide applications to mineral exploration, initiation of petroleum products, environmental applications in tracking radiolysis in organic matter

Alex Holman, Kliti Grice, Paul Greenwood, Katy Evans 132°00’ 141°30’ 11°00’  ARAFURA SEA Hosted in the Barney Creek Arnhem Formation (BCF), McArthur Inlier

Basin, NT GULF OF CARPENTARIA  Host rocks dated at 1.64 Batten Fault 1 Pine Zone HYC billion years old Creek Inlier  Part of the Proterozoic Mt. McArthur Isa / McArthur Pb-Zn Basin Murphy Walford Inlier Creek province Mt. Isa Basin  One of the world’s largest Century Dugald pre-Mesoproterozoic Lady Loretta River sediment-hosted Pb/Zn/Ag basement 2 Meso- to Paleoproterozoic Hilton & deposits (30 Mt Pb + Zn) intracontinental basin George Fisher Mount Isa Phanerozoic cover Cannington 22°30’

1 Page & Sweet 1998. Aus. J. Earth Sci. 45, 219 Modified from Ireland et al. 2004. Miner. Deposita 39, 143 2 Huston et al.2006. Econ Geol. 101, 1117

Emu SW A, B Fault NE BCF Lower McArthur Group dolomites, evaporites

Upper Tawallah Group clastics: sandstones, volcanics, shales

Wollogorang Formation shale, dolomite Lower Tawallah Group volcanics: mafic, felsic

basement granitic basement

A B evaporite kerogen carbonate PSB shale SRB Barney Creek Formation SOB clastics Py pyrite 1 (sandstones, volcanics) mineralised shale in BCF Py pyrite 2

Modified from Greenwood et al. 2013. Ore Geol. Rev. 50, 1

 Redox conditions of McArthur Basin? . Recent evidence suggests ferruginous basin (Fe2+ rich) 1

 Microbial of basin? . Previous studies hindered by alteration/overprinting 2-4 . Possible influence on redox conditions?

1 Poulton et al. 2010. Nat. Geosci. 3, 486 4 Williford et al. 2011. Earth Planet. Sci. Lett. 301, 382 2 Logan et al. 2001. Geochim. Cosmochim. Acta 65, 1345 5 Dick et al. 2014. Geo Res J 3-4, 19 3 Chen et al. 2003. Earth Planet. Sci. Lett. 210, 467

 Received samples analysed by Williford, Grice et al.  Five samples taken along the estimated flow path of mineralising fluid  Novel organic and inorganic techniques were applied to answer the previously- mentioned questions

Williford et al. 2011. Earth Planet. Sci. Lett. 301, 382

 Freely-extractable OM vulnerable to overprinting and alteration  Removal of silicate minerals with HF exposes Bitumen II from within mineral matrix  Bitumen II believed to be shielded from overprinting and alteration 1,2

1 Nabbefeld et al. 2010. Org. Geochem. 41, 78 2 Sherman et al. 2007. Org. Geochem. 38, 1987

16 18 Bitumen I 20 Williford et al. 22 14 24 26 28 30 32

26 28 30 Bitumen II 32 This study 24 18 16 34 22 20 36 38

 Bitumen II n-alkane distribution suggests contribution from sulfate-reducing and sulfide-oxidising bacteria (Melendez et al. 2013. Geology 40, 123)

-25

-27

-29

-31 C (‰) C

13 -33 δ -35

-37

-39 0 200 400 600 800 Distance from sample pit 1 (m) BI (C 18-21) BII (C24-32) Kerogen  Bitumen II appears indigenous to HYC  Low 13C depleted – contribution from SRB  Bitumen I possibly a later overprint  Evidence of SRB and SOB suggest that HYC was deposited under euxinic conditions

sourced from seawater sulfate or evaporitic deposits

 Sulfate reduced to sulfide by sulfate-reducing bacteria . Significant depletion in 34S (1)

+ -2 2 2 H + SO4 + 4 H2 → H2S + 4 H2O ( ) -2 - 2 SO4 + 2 CH2O → H2S + 2 HCO3 ( )

 Sulfide reacts with metal ions to precipitate sulfide minerals . Almost no isotopic fractionation (3)

1 Brunner & Bernasconi 2005. Geochim. Cosmochim. Acta 69, 4759 2 Canfield 2001. Rev. Mineral. Geochem. 43, 607 3 Seal 2006. Rev. Mineral. Geochem. 61, 633

 Sulfide can be oxidised to elemental sulfur (S0) and -2 34 polysulfides (Sx ), with slight S enrichment

- 0 - 1 2 HS + O2 → 2 S + 2 OH ( ) - 0 + -2 2 HS + (1-x) S → H + Sx (x = 2 to 5) ( )

 Polysulfides can incorporate into functionalised organic matter during diagenesis (3)

 Living cells also incorporate sulfate (biosynthetic sulfur)

1 Steudel 1996. Ind. Eng. Chem. Res. 35, 1417 2 Chen & Morris 1972. Env. Sci. Technol. 6, 529 3 Aizenshtat et al. 1995. ACS Symposium Series 612, 16

δ34S (‰) -20 -10 0 10 20 30 40 50

HYC kerogen

HYC S0

HYC pyrite (1)

HYC galena (2)

HYC sphalerite (2)

Barney Creek pyrite (3)

 Organic and elemental S similar to sulfide minerals  Sulfur source distinct from non-mineralised Barney Creek

1 Eldridge et al. 1993. Econ. Geol. 88, 1 2 Ireland et al. 2004. Econ. Geol. 99, 1687 3 Johnston et al. 2008. Geochim. Cosmochim. Acta 72, 4278

 External source of sulfate – derived from McArthur Basin evaporitic units 1 . Possibly carried with mineralising fluid

 Sulfate entered HYC sub-basin, was reduced to sulfide by sulfate-reducing bacteria 1,2,3 . Euxinic conditions created in sub-basin

1 Holman et al. 2014. Chem. Geol. 387, 126 2 Holman et al. 2012. Org. Geochem. 52, 81 3 Holman et al. 2014. Geochim. Cosmochim. Acta 139, 98  Thankyou to

Steve Macko and the organisers for invite to the Gift workshop