Geology and mineral resources of the Northern Territory · 2019. 7. 3. · Australia, central Western Australia, northwestern South Australia and possibly areas of South East Asia

Ahmad M and Munson TJ (compilers)

Northern Territory Geological SurveySpecial Publication 5

Chapter 30: Kalkarindji Province

Geology and mineral resourcesof the Northern Territory

BIBLIOGRAPHIC REFERENCE: Glass LM, Ahmad M and Dunster JN, 2013. Chapter 30: Kalkarindji Province: in Ahmad M and Munson TJ (compilers). ‘Geology and mineral resources of the Northern Territory’. Northern Territory Geological Survey, Special Publication 5.

DisclaimerWhile all care has been taken to ensure that information contained in this publication is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of its information. The Northern Territory of Australia gives no warranty or assurance, and makes no representation as to the accuracy of any information or advice contained in this publication, or that it is suitable for your intended use. You should not rely upon information in this publication for the purpose of making any serious business or investment decisions without obtaining independent and/or professional advice in relation to your particular situation. The Northern Territory of Australia disclaims any liability or responsibility or duty of care towards any person for loss or damage caused by any use of, or reliance on the information contained in this publication.

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Kalkarindji Province

Chapter 30: KALKARINDJI PROVINCE LM Glass, M Ahmad and JN Dunster

INTRODUCTION

During the early Cambrian, a widespread outpouring of sub-aerial basaltic lava covered a large area of northern Australia, central Western Australia, northwestern South Australia and possibly areas of South East Asia that have subsequently been rifted from Australia. Stratigraphically equivalent exposures of this volcanic succession have historically been given different names; these include the Antrim Plateau Volcanics, Nutwood Downs Volcanics, Helen Springs Volcanics and Peaker Piker Volcanics in the Northern Territory, and the Colless Volcanics (Bultitude 1976) in Queensland. Coeval basaltic and intrusive rocks

South Australia include the Table Hill Volcanics (Peers 1969, Jackson and van de Graaff, Veevers 2000, Glass and Phillips 2006) and informally named Boondawari dolerite (MacDonald et al 2005). The Milliwindi Dolerite (Hanley and Wingate 2000) and the informally named Mount Ramsay dolerite of the Kimberley region of WA (Glass 2002) are also included as a part of this igneous event. Based on geochemical and isotopic similarities, Glass (2002)

province, and named it the Kalkarinji Continental Flood Basalt Province, but later revised the spelling to Kalkarindji1

111° 114° 117°

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(former) NutwoodDowns Volcanics

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Colless Volcanics

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Kalkarindji Suite(outcrop extent)

Diamond drillhole

Probable minimum original extent of Cambrian large igneous event

0 250 500 km

A09-202.ai

(Glass et al 2006, Glass and Phillips 2006). Figure 30.1 shows the outcrop distribution and probable original extent of the province in Australia. Since it extends across a vast area in excess of 106 km2 (Glass and Phillips 2006) and was probably emplaced over a very short geological time interval,

sensuand Eldholm (1992). The name Kalkarindji Volcanic Group was erected by Kruse in Rawlings et al (2008) to include some components of the Kalkarindji Province in the NT and parts of WA, including minor intercalated sedimentary units.

units, this name is herein formally replaced by Kalkarindji Suite (see below).

NTGS airborne magnetic data (Clifton 2008) indicate

under covering strata across the Ord, Bonaparte, Daly, northern Wiso and northern Georgina basins. Figure 30.2a shows the extent of outcropping Kalkarindji Province rocks overlain on the First Vertical Derivative aeromagnetic image for an area within the Palaeo–Mesoproterozoic Birrindudu and Meso-?late Neoproterozoic Victoria basins of the

Figure 30.1

et al 2010).

Current as of October 2010

2 Names of 1:250 000 mapsheets are shown in large capital letters

1 The name Kalkarindji is derived from the place name in WAVE 2 (Gazetteer of Australia 2004).

Geology and mineral resources of the Northern Territory Special publication 5


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A09-205.ai

Kalkarindji flood basalt (outcrop extent) Location of Figure 30.2b

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Northern Territory. The magnetic imagery Figure 30.2b

traced under shallow cover. Kruse in Rawlings et al (2008) synonymised the

Nutwood Downs Volcanics in HODGSON DOWNS with the more extensive Antrim Plateau Volcanics. Subsurface contiguous volcanic and minor sedimentary rocks to the east of the Tennant Region are extensive beneath the central Georgina Basin. The names Helen Springs Volcanics and Peaker Piker Volcanics have been historically applied to these strata, but these names were synonymised by Kruse in Rawlings et al (2008) as Helen Springs Volcanics.

Historically, Hardman (1885) and Jensen (1915) provided the earliest descriptions of the Antrim Plateau Volcanics in the East Kimberley and Victoria River regions of northern Australia. Hardman (1885) named hilly dissected country, to the east of the Elvire River in the eastern Kimberley district, as the Great Antrim Plateau. Thirty years later, Jensen (1915) documented and described volcanic rocks in the Victoria River, Edith River and Daly River regions, and suggested they were most likely to be of Carboniferous or Permo-Carboniferous age. David

on the description of the Great Antrim Plateau of Hardman (1885). However, this name was changed by Traves (1955) to

units. Edwards and Clarke (1941) undertook a petrographic study of basalts in the eastern Kimberley region, where they described the rocks as ranging from olivine basalt to quartz basalt. They suggested that the eastern Kimberley basalts

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0 25 km A09-251.ai

Neave Fault

b

Figure 30.2. (a) Kalkarindji Suite outcrop extent (green areas) overlain on First Vertical Derivative aeromagnetic image (Clifton 2008) for a selected area within Birrindudu and Victoria basins,

b) Red boxed area

Green areas indicate Kalkarindji outcrop extent.

Figure 30.2b


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formed a single basaltic province. Traves (1955) described the basalts in the Ord–Victoria River region and suggested that isolated suites of Cambrian basalts across northern Australia perhaps belonged to a single period of volcanic activity. A

relationships, petrography and chemistry of the Antrim Plateau Volcanics as a part of their study of the northern Wiso Basin. Dunn and Brown (1969) suggested a correlation of stratigraphically equivalent early Cambrian volcanic rocks in other parts of the Northern Territory and Queensland with the more extensive Antrim Plateau Volcanics. Bultitude (1971, 1976) subsequently provided a more detailed description of the stratigraphic succession, chemistry and mineralogy of these volcanic rocks and reinforced the possible correlation of

and Beere (1988) also provided a detailed description of basalts in the Bonaparte and Ord basins and indicated a maximum

recently, Glass (2002) undertook a comprehensive study of the mineralogy, geochemistry, geochronology and petrogenesis of the entire province.

The volcanic rocks consist predominantly of basaltic

intrusive dolerite dykes that are found in Western Australia. Thin interbeds (generally <10 m thick) of well sorted cross-bedded sandstone, siltstone, chert, sedimentary breccia and

Conophyton sp) are locally present (Sweet et al (1974b).

EARLY CAMBRIAN

Kalkarindji Suite

formalised as the Kalkarindji Volcanic Group (Kruse in Rawlings et alvarious minor intercalated and immediately underlying sedimentary units. However, given the dominance of the

(see Appendix), so as to include volcanic and intrusive constituents (see Geoscience Australia Stratigraphic Units Database website). Minor intercalated sedimentary components of the former Kalkarindji Volcanic Group are

Suite, but are included within the constituent formations.The Antrim Plateau Volcanics (Traves 1955)

unconformably overlie Proterozoic basement rocks and underlie sedimentary rocks of the Ord, Daly, northern Wiso and northern Georgina basins in the NT, and the Ord, Bonaparte and eastern Kimberley basins in Western Australia. The unit may extend further to the north in the Arafura Basin, as red-brown volcanic rocks in drillhole Money Shoal-1 (Figure 30.1) have historically been correlated with the Antrim Plateau Volcanics (Petroconsultants Australasia 1989). Moreover, regional thermal subsidence in the Arafura Basin has been attributed to Antrim Plateau volcanism (Struckmeyer 2006).

Sweet et al (1974b) described and formally named intercalating agglomerate (consisting of extensively

altered angular to rounded fragments of vesicular and amygdaloidal basalt set in an aphanitic, heavily altered basaltic matrix), minor basaltic lavas and thin lenses of sandstone and siltstone in the southern Victoria River region as the Blackfella Rockhole Member. The volcanic detritus in agglomerate bands is thought to have been derived from highly explosive volcanic activity and the presence of thin lenses of sandstone and siltstone within agglomerate bands is indicative of pyroclastic deposition under sub-aqueous conditions. Sweet et al (1974b) also described and formally named glomeroporphyritic (in this case, grouping of plagioclase phenocrysts into distinct clusters) and often columnar jointed basalts in the same region as the Bingy Bingy Basalt Member. The Blackfella Rockhole and Bingy Bingy Basalt

the intercalated Mount Close Chert Member. There are at least ten other intercalated sedimentary units mapped in the NT. Correlation of sedimentary and volcanic units is hampered by poor outcrop and their generally limited areal extent, but a suggested correlation for the Victoria River region is shown in Figure 30.3. The units include widespread carbonate, agglomerate and pyroclastic

bottoms, and sandstone beds, which are generally of more limited areal extent and typically less than 10 m thick. The sandstones are typically cross-bedded and are variously tuffaceous, quartzic, feldspathic or ferruginous. Many of the carbonate units were originally stromatolitic,

Figure 30.3 indicates that the Bingy Bingy Basalt Member extends

Member in WA indicates that carbonate deposition

limestone and matrix-supported basalt breccia that might be the original rock now represented by the Mount Close Chert Member at the surface. However, it has been suggested by Walter (1972) that conical stromatolites from the constituent Mount Close Member (Mory and Beere 1988) of the Antrim Plateau Volcanics in WA, may represent a hot springs environment, in which conical stromatolites are known to develop even up to the present (Walter et al 1976). They therefore do not provide an age constraint. Nevertheless, recent isotopic dating results (see Geochronologyage for the volcanic rocks. Also intercalated within the Antrim Plateau Volcanic succession is the Malley Spring Member (Mory and Beere 1985). This is a 3–5 m-thick siltstone and sandstone unit that occurs about 50 m above the base of the Antrim Plateau Volcanics over a distance of 25 km in the Ord Basin in WA.

Units that were previously included in the Kalkarindji Volcanic Group of Kruse (in Rawlings et al 2008) include the 'Jarong Conglomerate' (Pontifex and Mendum 1972, Sweet et al 1974a), which is now subsumed as the Uniya Formation (see Wolfe Basin), the Kinevans Sandstone (Sweet et al 1974b; see Wolfe Basin) and the Jindare Formation



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(Needham and Stuart-Smith 1984, Kruse et al 1994). The

conformably underlie the Antrim Plateau Volcanics in the Victoria River Region (Kruse in Rawlings et al 2008). The

quartzofeldspathic sandstone, often with characteristic low-

localised conglomerate, that laterally interdigitates with the Antrim Plateau Volcanics along the northeastern margin

shoreface, ?marine environment (Kruse et al 1994, Kruse in Rawlings et al 2008).

The Antrim Plateau volcanic succession has its greatest thickness in the eastern Kimberley region, where successive

800 m and 600 m thickness were measured by Glass (2002)

trigonometric station J32 of Hardman (1885) in GORDON DOWNS in the Kimberley region, respectively (Figure 30.4). Minor interbedded siltstone units are present at about 100 m from the base of the succession at Purnululu National Park.

form prominent mesas capped by resistant agglomerate and

Figure 30.5). The mesas are remnants of a much greater land surface dissected by modern-day stream systems. A BMR drilling project in the

Victoria River region resulted in nine stratigraphic drillholes (Bultitude 1971, Figure 30.6) and a maximum thickness

(Figure 30.7). However, this is a minimum thickness for basalt in this region, as the drillhole was terminated while

Springs area, the Antrim Plateau Volcanics attain a thickness of about 250 m and in the Tanami Region, it is less than 30 m in thickness (Blake et al (2005) described intersections of almost 500 m of basaltic

overlying basalt breccia, is correlated with units in drillhole ANTD001, about 20 km away.

The Antrim Plateau Volcanics unconformably overlie Proterozoic basement of various ages in the eastern Kimberley region of Western Australia. This includes the Neoproterozoic Albert Edward Group (Dow and Gemuts 1967), where the contact is a narrow thermal aureole in sandstone. The volcanics probably unconformably overlie the Moonlight Valley Tillite of the Wolfe Basin in AUVERGNE (Dunster et al 2000).

unconformably overlie the Proterozoic Wattie, Bullita and Tijunna groups (Birrindudu Basin) and Auvergne Group (Victoria Basin; Beier et alDOWNS, the Antrim Plateau Volcanics (former Nutwood Downs Volcanics) unconformably overlie the Bukalara

suggested for the Bukalara Sandstone due to the presence of tube-like structures thought to be the trace fossil Skolithos sp (Muir 1980). Dunnet (1965) and Plumb and

_Cla

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Massive porphyritic and tholeitic basalt

Friable cross-bedded quartz sandstone with some surface silicification

Interbedded chert and sandstone

Agglomerate, highly weathered andlateritised in places

Laminated chert, stromatolitic in part (Mount Close Chert in WA)

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Blackfella Rockhole Member Interbedded basalt and agglomerate, minor intercalated sandstone

Grey tuffaceous sandstone with angular chert fragments near base,minor dark grey chert interbeds

Bingy Bingy Basalt Member Medium-grained glomeroporphyrtic

AuvergneDelamereLissadell

WADixon Range

WAWave Hill LimbunyaV.R.D.WaterlooFergusson

River

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Figure 30.3. Suggested lithostratigraphic correlation of mapped units within Antrim Plateau Volcanics in the Victoria River Region, based on surface mapping, which does not preclude the presence of other units in the subsurface (from unpublished 2000 work by JN Dunster). Unit symbols are as depicted on published mapfaces.


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Roberts (1965) similarly interpreted structures in the correlative Buckingham Bay Sandstone (Arafura Basin) as Skolithos sp. However, Haines in (Rawlings et al 1997) reinterpreted these structures as being abiogenic

sandstones containing these structures are more likely to

In general, the Antrim Plateau Volcanics are unconformably overlain by early middle Cambrian carbonate units: Headleys Limestone of the Ord Basin (Mory and Beere 1988); Montejinni Limestone of the Wiso Basin (Randal and Brown 1967); and Tindall Limestone of the Daly Basin (Kruse et al 1994). In Katherine, palaeontological evidence indicates that the Tindall Limestone can be referred to the late Ordian stage of the Australian middle Cambrian (Kruse et al 1994, Laurie 2006).

The Helen Springs Volcanics (Noakes and Traves

and also occur extensively in the subsurface in the northern and central Georgina Basin (Kruse 2008). The volcanics are synonymous with the former Peaker Piker Volcanics (Kruse in Rawlings et al 2008); these outcrop in the northeastern Georgina Basin, and unconformably

South Nicholson Group (South Nicholson Basin) and sedimentary rocks of the McArthur Basin. The Helen Springs Volcanics are disconformably overlain by the middle Cambrian Gum Ridge Formation, Wonarah Formation and Top Springs Limestone of the Georgina Basin (Randal et al 1966, Kruse et al 2010). A sedimentary unit containing peperite, the Muckaty Sandstone Member forms the base of the Helen Springs Volcanics to the east of the Tennant Region in HELEN SPRINGS (Hussey et al 2001). The Helen Springs Volcanics are 9 m thick in cored drillhole NTGS96/1 in central HELEN SPRINGS (Kruse 1996, Hussey et al 2001), and the unit reaches a maximum thickness of 156 m in cored drillhole AY06DD01 in southeastern ALROY (Kruse 2008). The former Peaker Piker Volcanics are 16 m thick in drillhole DD83SC1 in WALHALLOW (Dunster 2009).

Close to the Queensland–Northern Territory border, the Colless Volcanics (Carter and Öpik 1961) form small exposures on the margins of the eastern Georgina Basin in LAWN HILL, western Queensland. This unit consists of amygdaloidal basalt and other tholeiitic lavas outcropping over only a few square kilometres at the southern end of the Constance Range, where they unconformably overlie the South Nicholson Group. The volcanic rocks are unconformably overlain by the Thorntonia Limestone of the Georgina Basin.

Table Hill Volcanics are conformably underlain by the Wahlgu Formation and Lungkarta Formation, and overlain by the Paterson, Lennis and Wanna Formations. The Boondawari dolerite (MacDonald et al 2005) is a feeder dyke to the volcanic suites. The former Kulyong Formation

superseded by the Table Hill Volcanics) is underlain by the Trainor Hill Sandstone and overlain by the Mount Chandler

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Kalkarindjioutcrop extent

Figure 30.4. Stratigraphic sections for Kalkarindji Suite. (a) East–west transect at Purnululu National Park, DIXON RANGE, and (b) east–west transect at trigonometric station J32 of Hardman

Glass 2002).



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Sandstone. Possible early Cambrian basaltic rocks in association with known tuffs have also been observed by J Dunster in petroleum exploration drillholes to the extreme

Cadney Park Member. More recently, geochemically similar rocks of the same age as the Kalkarindji Suite have been

et al 2010).Eruptive centres for the Antrim Plateau Volcanics (ie

Kalkarindji Suite) are not easily recognisable, possibly because

1976); however, swarms of small, altered and brecciated dykes cut the volcanic rocks around the south-southeastern extremity of the Hardman Syncline (part of the Ord Basin). These dykes consist of angular fragments of massive to slightly

outcropping feeder dykes to the Kalkarindji province are not evident in the Northern Territory, First Vertical Derivative

long structure under cover that may represent a lava river

(Figure 30.8). Outcropping dolerite dykes, interpreted to be feeder dykes to the Kalkarindji Province, are present in the western Kimberley region of Western Australia (Hanley and Wingate 2000, Glass 2002), the most prominent being the 250 km-long Milliwindi Dolerite (Hanley and Wingate 2000,

Figure 30.1), which intrudes Palaeoproterozoic rocks of the

Geochronology

Bultitude (1972) provided the earliest geochronological studies for the Kalkarindji Province and obtained K-Ar ages of 511 ± 12 Ma and 500 ± 12 Ma, as recalculated by Glass (2002) using the decay constants of Steiger and Jäger (1977), for the Helen Springs and former Nutwood Downs Volcanics, respectively. At the time the data were generated, they were assumed to be erroneously young as they were inconsistent with known stratigraphic constraints (Bultitude 1972, 1976). Hanley and Wingate (2000) obtained a U-Pb

Dolerite, a feeder dyke to Kalkarindji basalts in Western Australia. Glass and Phillips (2006) reported high-precision 40Ar/39Ar ages for plagioclase feldspar separates for basalts from the Helen Springs Volcanics and Antrim Plateau Volcanics. The data have an age range between 508 ± 2 Ma

of 507 ± 4 Ma, which places the Kalkarindji eruption event close to the early–middle Cambrian boundary (Glass and Phillips 2006). The oldest age (within error) is compatible with the position of the volcanic rocks below the securely dated Cambrian sequence 1 (Ordian) interval of Shergold et al

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Figure 30.5

River region, NT.


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results are in agreement with known age constraints for the Table Hill Volcanics, which include a K-Ar whole rock age of 500 ± 14 Ma (as reported in Veevers 2000), a 207Pb/206Pb zirconolite age of 504 ± 18 Ma (Stern et al 2005) and an 40Ar/39Ar age of 505 ± 3 Ma (Evins et al 2009). Moreover, MacDonald et al

Petrology

plagioclase-phyric basalt. The basalt mineral assemblage comprises plagioclase, clinopyroxene (augite or pigeonite) rare orthopyroxene with lesser ilmenite, titanomagnetite, primary and secondary quartz and K-feldspar (Glass 2002). Olivine, mica and hornblende are accessory components (Bultitude 1971). Glass (2002) described the petrology of the Kalkarindji basalts in some detail and this is summarised

aphanitic rocks to porphyritic and coarse-grained rocks approaching doleritic textures. The primary phenocryst and microphenocryst phases are subhedral clinopyroxene, near-euhedral plagioclase feldspar and, in the most evolved rocks, abundant quartz. Secondary phases include chlorite,

NORTHERNTERRITORY

Waterloo-2Waterloo-1

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Figure 30.6shown in Figure 30.7) in Victoria River region. Kalkarindji Suite outcrop extent shown by green areas, derived from GA 1:1M

Figure 30.7



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17°

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ALICE SPRINGS

DARWIN

Figure 30.8. First Vertical Derivative aeromagnetic image, derived from Clifton (2008), showing section of large curvilinear structure

Figure 30.9. Scanning Electron Microscope (SEM) photomicrographs of Kalkarindji Suite basalts (from Glass

a) Coarse-grained Helen Springs Volcanics

and plagioclase. (bshowing ophitic texture. (c) Antrim Plateau Volcanics

plagioclase compositions: An49 and An61.

a

c

b


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albite, K-feldspar, quartz and titanite. Rocks that have undergone hydrothermal alteration are commonly chloritic

prehnite, malachite, calcite and silica. Groundmass phases are mostly coarse to medium-grained, ophitic to granular and intergranular (euhedral plagioclase laths and subhedral

rocks, intersertal textures dominate due to the presence of

rocks may contain late-crystallising potassic and sodic feldspar and quartz. Scanning Electron Microscope (SEM) photomicrographs (Figures 30.9a–c) show textural petrographic relationships for the Helen Springs Volcanics and Antrim Plateau Volcanics. Feldspar compositions for all Kalkarindji rocks, range from An49 to An72 and pyroxene compositions include high-Cr pyroxene (Cr-diopside), Ca-rich clinopyroxene (augite), pigeonite and orthopyroxene.

between clinopyroxene and plagioclase (Figure 30.9a).

the Kalkarindji basalts range from olivine-hypersthene

levels are transitional between quartz tholeiite and olivine normative tholeiite.

Geochemistry

Geochemical signatures for the Kalkarindji Province basalts were described in some detail by Glass (2002) and Glass and Phillips (2006), and the most distinctive feature for the basalts is the overall geochemical homogeneity across the entire province. Glass and Phillips (2006) further demonstrated that the Antrim Plateau Volcanics and the stratigraphic equivalents (ie Helen Springs Volcanics, former Nutwood Downs Volcanics, former Peaker Piker Volcanics, Boondawari dolerite and Table Hill Volcanics) are

geochemically indistinguishable (Figure 30.10). A genetic link between the Table Hill Volcanics and the Antrim Plateau Volcanics has been further reinforced by M Gole (consultant geologist, pers comm 2003), based on the evaluation of a substantial number of geochemical analyses of the former unit. More recent work by Evins et al

for Fe2O3for most basalts cluster between 65 and 50. The Kalkarindji

(HFSE) abundances, eg low elemental abundances of Ta, P, Ti and Nb relative to the incompatible elements. The basalts and dolerites further show extreme enrichment in the most

compositions and more similar to continental crustal compositions. These distinctive geochemical characteristics serve to distinguish the Kalkarindji basalts from all other large igneous provinces worldwide (Glass 2002).

Platinum Group Elements (PGE) abundances are extremely low, in most cases below the detection limit (Glass

the basalt petrogenesis. Depletion in the PGE may indicate

which would have resulted in the sequestering of chalcophile elements; this has implications for nickel prospectivity for the Kalkarindji Suite. Similar depletions in PGE patterns to

et al 1993), which is host to World-class nickel mineralisation.

Structure

Kalkarindji basalts are the basal unit of a number of Palaeozoic basins across northern Australia, including the northern Wiso, Daly, Bonaparte, Ord and northern Georgina Basins. Although these basins were attenuated, rifting

Helen Springs Volcanics Mg# = 60Former Nutwood Downs Volcanics Mg# = 52Former Peaker Piker Volcanics Mg# = 44Boondawari dolerite Mg# = 59Table Hill Volcanics

Antrim Plateau Volcanics

Mg# = 60

100

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ve M

antle

Cs Rb Ba Tn U K Ta Nb La Ce Sr P Nd Hf Zr Sm Ti Dy Y Yb Sc V

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Figure 30.10. Primitive-mantle normalised element abundance diagram showing range for Antrim Plateau Volcanics (green) overlain by data for Antrim Plateau basalt stratigraphic

Springs Volcanics, former Nutwood Downs Volcanics, former Peaker Piker Volcanics, Table Hill Volcanics and Boondawari dolerite (feeder dyke for the Table Hill Volcanics). Normalising values from McDonough and Sun 1995.

) for Fe2O3



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never went to completion. The basalts attain their greatest thickness in the East Kimberley region, east of the Halls Creek Orogen and this led Mory and Beere (1988) and Glass (2002) to suggest that this region was most likely the major eruptive centre for Kalkarindji volcanism. However, given the dimensions of the province, an extensive dyke system for the basalts is most likely concealed, possibly by subsequent

and Wingate 2000, Glass 2002) and the informal Mount Ramsay dolerite (Glass 2002) in the southwest Kimberley region are the only known exposed dyke systems interpreted

(2006) interpreted a major NNW-trending structural axis in

anomalies as the main axis of doming, magma injection and extrusion of magma. They further suggested that sites for intrusion may have occurred along east-northeast-trending structures (eg, the West Baines, Neave and Rosewood faults), which they interpreted as transform faults that developed parallel to crustal extension.

Although concealed under cover, the prominent Neave Fault (Figures 30.2a, b) and less obvious Negri Fault appear

between the Neave Fault and the Antrim Plateau Volcanics may represent any of the following:

1. a large structure which has offset basaltic lavas to the north that have subsequently been eroded

2. a fault scarp palaeotopographic feature which

3. a feeder conduit to the basalts.

a prominent structure, appears to displace the Antrim Plateau Volcanics and Angalarri Siltstone by only about 100 m (Sweet 1973b). Minor displacement of the Antrim Plateau Volcanics and the Moonlight Valley Tillite occurs on the northern extension of the Blackfella Creek Fault

Possible link to early–middle Cambrian mass extinction

High-precision 40Ar/39Ar ages, established by Glass and Phillips (2006), indicate that the Kalkarindji eruption event occurred close to the early–middle Cambrian boundary. This timing is coincident with a major global mass extinction event which corresponds to the Toyonian stage of the early–middle Cambrian (Zhuravlev and Wood 1996). This mass extinction occurred after the rapid appearance of many marine invertebrates in early Cambrian time (Brasier et al 1994) and the Toyonian mass extinction appears to have been pronounced for the Australian region

et al (2006) 34S from Georgina Basin

samples at about the early–middle Cambrian boundary, which they attributed to ocean anoxia combined with increased perturbations of oceanic sulfate. They suggested greenhouse warming as a result of volcanic eruptions of

for the collapse of early metazoan reef ecosystems during the latest early Cambrian.

Petrogenesis

Petrogenetic modeling of Kalkarindji Province basalts by Glass (2002) established that the basalts can be successfully modeled by crustal contamination processes of a primary asthenospheric source composition. The original source magmas assimilated

Australian Felsic Crust (NAFC), Glass (2002), Glass et al (2006). Glass (2002) further calculated that the Kalkarindji primary picritic melts (in equilibrium with mantle olivine) segregated from their mantle source at pressures of about 15 to 20 kbar, which is equivalent to a depth of 50–70 km. However, in Neoproterozoic times, ca 200 km-thick lithosphere would have underlain the postulated future eruptive centre for Kalkarindji magmatism (see Glass 2002). Some type of tectonic process, therefore, must have substantially thinned the lithosphere prior to Kalkarindji magmatism. A mantle plume source to generate the melts is feasible, providing

segregation. Catastrophic lithospheric delamination, accompanied by substantial asthenospheric melt segregation, may be another mechanism to account for

MINERAL RESOURCES

Copper

Work by the BMR in the 1950s and 1960s, and later by the Northern Territory Geological Survey (eg Cutovinos et al

units of the Antrim Plateau Volcanics, near and along

Ord Basin. Some copper was also noted in the overlying limestone close to the contact zone. A total of 19 recorded mineral occurrences are known in the NT (NTGS MODAT

selected copper occurrences in the Victoria River district are shown in Figure 30.11.

Extensive exploration for copper was conducted in the NT during 1968–1970 by a joint venture led by Metals

large copper deposits (similar to copper mineralisation

Antrim Plateau Volcanics (Erskine et al 1970s, Amoco Minerals Australia Co, led an exploration program to test for copper mineralisation at the Antrim

styles of copper mineralisation were distinguished in these early studies (Erskine et al 1970, Burt et al 1970, Miguel 1974):

Structurally controlled copper mineralisation in fault and shear zones (eg malachite and chalcocite associated with fault and shear zones at the Caves prospect).Copper mineralisation in the basal three metres of the

and azurite).


30:11


Copper mineralisation associated with secondary

massive basalt in the upper Antrim Plateau Volcanics (native copper, chalcopyrite, cuprite, chalcocite and malachite).Copper mineralisation associated with agglomerate (chalcocite, malachite associated with barite veins).Finely disseminated native copper and chalcopyrite in

Copper mineralisation linked with black manganiferous limestone mounds of possible fumarolic origin (hot seeps).

The best documented copper prospect located during these exploration activities, Caves (Figure 30.11), is

et al (1970) reported

The highest grade mineralisation is controlled by a series of faults in agglomerate of the Antrim Plateau Volcanics

at the prospect may be related to the northwest-trending, steeply dipping Negri Fault, which displaces the Headleys

malachite, chalcocite and azurite (Sweet et al 1974b). A circular body of fumarolic (hot seep) deposits occurs adjacent to the visible mineralisation. These contain disseminated, but low-grade copper.

Randal and Brown (1967) reported the occurrence of native copper in basalt of the Antrim Plateau Volcanics from the BMR Shoeing Tool Replacement Bore, located in

quartz-malachite-cuprite veins and native copper in vesicular basalt near Montejinni homestead. Crowsons Prospect, located 11 km west of Montejinni homestead, was found by W and B Crowson of Montejinni Station in the late 1960s. Native copper, cuprite, malachite, chalcocite and traces of covellite were reported from the Antrim Plateau Volcanics near the contact with the

limestone, or forms thin (up to 1 mm) veinlets following silty laminations in the limestone. Specimens better than

(Sampey Exploration Services 1968), but individual

(Sakurai 1991). Thomson (1951) reported the occurrence of nuggets

of native copper up to 4 kg in weight at Campbells

Plateau Volcanics or within soil overlying this unit and

rocks. However, subsequent exploration and visits by Government geological surveys failed to relocate the site. No other copper nuggets were found and no disseminated copper is present in the basalt at this location.

The Antrim Plateau Volcanics and associated rocks are currently being explored for copper in WA and NT

their Copper Flats Project. The Michigan Copper Belt is

being used as an analogue. Work to date has focused in WA and has included encouraging rock chip samples that

Nickel

in Russia, which are host to large Ni-Cu-PGE deposits. Several companies have used this analogy as the basis for a conceptual exploration model targeting nickel in feeder systems to the Antrim Plateau Volcanics (eg Gole and

suitable feeders or nickel of economic grade.

KEEP River

TIMOR

SEA

JOSEPH

BONAPARTE

GULF

RIVER

Victoria

Fitzmaurice River

Daly River

South Alligator R.

PORT KEATS

AUVERGNE

WATERLOO

LIMBUNYA

BIRRINDUDU

CAPE SCOTT

FOG BAY

FERGUSSON RIVER

DELAMERE

VICTORIA RIVER DOWNS

WAVE HILL

WINNECKE CREEK

NEWCASTLEWATERS

SOUTH LAKEWOODS

PINE CREEK

DARWIN

DarwinALLIGATOR RIVER

KATHERINE

LARRIMAH

DALY WATERS

Crowsons Prospect

Byrnes Hill

Matilda Creek

Campbells Springs

Caves

MOUNT EVELYN

East Baines R

.

Vic

toria

R.

Victoria R.

Victoria Hwy

Stuart Hwy

Buchanan Hwy

Caves

DELAMERE

Kalkarindji Suite locality

1:250 000 mapsheet

Copper occurrence

DarwinA09-256.ai

Figure 30.11region, NT. Kalkarindji Suite outcrop extent shown by green



30:12

Barite

Pods and veins of barite in the Antrim Plateau Volcanics are commonly associated with quartz and calcite (Sweet et al 1974b). Several of the largest deposits have been evaluated for possible use as a weighting agent for drilling mud. The poor colour quality generally precludes other industrial uses.

Bingy Bingy Basalt Member contains a resource of barite occurring as lenticular lodes.

contains 261 039 t to a depth of 20 m. This material meets

1988). A barite deposit at Mathison Creek (FERGUSSON

occupy a fracture in the volcanic rocks and are parallel to a southeasterly regional trend (Sweet et al 1974b). Two veins

3 4

gravity of 4.54 g/cm34 (Willis

and Newton 1975). Total production from the two lodes was 35 000 t, but only the top 4–5 m of lode material was mined. The estimated resource was 32 800 t per vertical metre (Mendum 1972) and a total barite resource was estimated at 475 000 t to 20 m depth (Ransom 1980).

Bitumen

There is anecdotal evidence of widespread bitumen within Antrim Plateau basalts in the Sturt Plateau region on the NT (Matthews 2009). Recent drilling by Dunmarra

seams within Antrim Plateau Volcanics host rocks south of Mataranka township (Matthews 2009). The bitumen

vein was approximately 5 cm in thickness (Figure 30.12).

Although the presence of bitumen appears to be widespread in this region, target generation for bitumen seams within

Gemstones and semi-precious minerals

Amethyst, smoky quartz, blood red quartz locally called

vesicular basalt of the Antrim Plateau Volcanics (Traves 1955, Sweet et al

minerals occur as geodes and amygdales. Dunster (2005) described specimen-quality amethyst

(Figure 30.13) that has been collected since the 1950s and was mined on a small scale. One such mine, located 20 km

during 1993 and subsequently closed. At this locality, an open joint up to 0.5 m wide, striking 205º and dipping 70º northwest in the Antrim Plateau Volcanics contains short and thick amethyst crystals up to 5 cm long and 5 cm wide on both walls of the opening. The crystals are coated with iron oxides and have a pitted surface. Approximately 500 kg of amethyst was recovered from vertical, north-oriented mineralised joints within the basalt on Moolooloo Station. Similarly, about 400 kg, including faceting-grade amethyst was recovered from a mineral claim in the Victoria River Downs area. Amethyst also

larger lined amygdales from this location have been sold as mineralogical specimens (Dunster 2005).

Figure 30.14a) was discovered in the Wave Hill area of the Northern Territory in the 1950s. During the 1960s, several local fossickers sold quantities of this material to dealers in Victoria. Some of the prehnite was sent to Germany for carving, but nothing more was mined until the late 1990s (Dunster 2005). Two companies currently hold exploration licenses and mining tenements for prehnite and hope to market the best-quality material. Bulk samples have been collected, and some material has been carved and tumbled (Figure 30.14b) and evaluated overseas.

Figure 30.12. Chips of bitumen from drillhole SPBP 6 (photo from Matthews 2009).

Figure 30.13. Gemstones hosted within Antrim Plateau Volcanics

courtesy of A Wygralak, NTGS).


30:13


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APPENDIX: NEW STRATIGRAPHIC DEFINITION

Kalkarindji SuiteExtentProposers

Derivation of name: Kalkarindji township, located

originally named Kalkarinji Continental Flood Basalt Province by Glass (2002); spelling of name was subsequently revised by Glass and Phillips (2006) to Kalkarindji.

Constituent unitsunits: Antrim Plateau Volcanics (Traves 1955), including Bingy Bingy Basalt Member and Blackfella Rockhole Member in NT and WA (both Sweet et al 1974b); Helen Springs Volcanics in NT (Noakes and Traves 1954); Colless Volcanics in Qld (Carter 1959); Milliwindi Dolerite (Hanley and Wingate 2000); informal Mount Ramsay dolerite in WA (Glass 2002); Table Hill Volcanics, including informal Boondawari dolerite (MacDonald et alBasin in WA (Jackson and van de Graaff 1981).

Unit name history, synonymy: Replaces Kalkarindji Volcanic Group of Kruse in Rawlings et al (2008), which

included sedimentary units (see Comments). Synonymy for constituent units: Antrim Plateau Volcanics includes Great Antrim Plateau (Hardman 1885), Antrim Plateau Basalts

Volcanics (Beattie and Brown 1984) Antrim Plateau Volcanics are synonymous with Nutwood Downs Volcanics (Dunn 1963; see Kruse in Rawlings et al 2008); Helen Springs Volcanics are synonymous with Peaker Piker Volcanics (Smith and Roberts 1963; see Kruse in Rawlings et al 2008); Table Hill Volcanics are synonymous with Kulyong Volcanics in SA (see W Cowley and R Hocking in GA Stratigraphic Names database).

Extent: Basal unit of a number of Palaeozoic basins across northern Australia, including the northern Wiso, Daly, Bonaparte, Ord and northern Georgina basins. Widespread outpouring of sub-aerial basaltic lava that covered a large area of northern Australia, central Western Australia and western South Australia

Lithology: Tholeiitic basalt and dolerite with massive, porphyritic, partly vesicular, amygdaloidal

breccia, peperite, pyroclastic deposits.Thickness: Greatest thickness is in east Kimberley region

of Western Australia. Antrim Plateau Volcanics: maximum

Western Australia (Mory and Beere 1988); stratigraphic section approximately 800 m at Purnululu National Park,

maximum 94 m in cored drillhole BN04DD01 in BRUNETTE DOWNS, beneath central Georgina Basin (Kruse et al 2008). Colless Volcanics: probable minimum 60 m (Carter 1959). Table Hill Volcanics: maximum 116 m in drillhole Hunt

Age and evidence: K-Ar age of 511 ± 12 Ma and 500 ± 12 Ma for Helen Springs and Nutwood Downs Volcanics (Bultitude 1972). Further radiometric dating provides an age of latest early Cambrian (early–middle Cambrian boundary)

for the Milliwindi Dolerite, a feeder dyke for the Antrim Plateau Volcanics in Western Australia (Hanley and Wingate 2000); 40Ar/39Ar ages of 508 ± 2 Ma and 505 ± 2 Ma (average 507 ± 2 Ma) for plagioclase feldspar separates for Helen Springs Volcanics and Antrim Plateau Volcanics in the

zircon age of 508 ± 10 Ma for the Boondawari dolerite, a

(MacDonald et al 2005); K-Ar whole rock age of 500 ± 14 Ma (reported in Veevers 2000) and 40Ar/39Ar age of 505 ± 3 Ma (Evins et al 2009) for the Table Hill Volcanics; The age of the igneous event is therefore ca 510 Ma.

Type locality: Very well exposed, 760 m-thick, east–west stratigraphic section through Antrim Plateau

in eastern Kimberley region from WGS84 52K 426414mE

unconformably overlie Mount Forster Sandstone of Albert Edward Group (contact well exposed) and are unconformably


30:17


Reference sections: Reference section 1: East–west

trigonometric station J32 of Hardman (1885) GORDON DOWNS (approximately 600 m thick) from WGS84 52K

Plateau Volcanics are unconformably overlain by Headleys

Group (Glass 2002). Reference section 2: continuously cored vertical drillhole ANTD002 through Antrim Plateau

thick). Reference section 3 for Helen Springs Volcanics:

Helen Springs Volcanics occur from 99.1–155.9 m (56.8 m). Reference section 4 for Table Hill Volcanics: continuously cored drillhole BMR Westwood-1, about 210 km SE of Table

Table Hill Volcanics is 71 m thick in this drillhole.Type sections of constituent formations. Antrim Plateau

thick), Western Australia (see Mory and Beere 1985, p38, 1988, p10, for grid coordinates); Helen Springs Volcanics:

et al 2001); Colless Volcanics: at about GDA94 54K 216029mE

Australia (see Jackson and van de Graaff 1981). Description at type locality: Basalts are well exposed

over a 760 m-thick east–west stratigraphic section. Exposed basal contact with Mount Forster Sandstone (Albert Edward

massive and medium-grained, then become more porphyritic up-section. Glomeroporphyritic basalts have small localised

Basin (Glass 2002).Relationships and boundary criteria: Antrim Plateau

Volcanics and Helen Springs Volcanics unconformably overlie

known underlying units are Neoproterozoic: Moonlight Valley Tillite, beneath Antrim Plateau Volcanics in AUVERGNE (Dunster et al 2000); and possibly younger (late Neoproterozoic; Rawlings et al 1997) Bukalara Sandstone beneath Antrim Plateau Volcanics in HODGSON DOWNS. Unconformably

2006) carbonate units: Tarrara Formation of Bonaparte Basin,

central and eastern Georgina Basin. Unconformably overlain by later middle Cambrian Wonarah Formation in central

Conglomerate and in GORDON DOWNS, Antrim Plateau Volcanics unconformably underlies various components of Albert Edward Group. Milliwindi Dolerite and Mount Ramsay dolerite are interpreted as feeder dykes to the volcanic suites. Table Hill Volcanics are underlain by Wahlgu Formation

dolerite (MacDonald et al 2005) is interpreted as a feeder dyke to the volcanic suite. The former Kulyong Formation

superseded by Table Hill Volcanics) is underlain by Trainor Hill Sandstone and overlain by Mount Chandler Sandstone. Colless Volcanics overlies Mullera Formation, and underlies

Structure and metamorphism: The major eruptive centre is most likely in east Kimberley region of WA.

Ramsay dolerites (exposed) and Boondawari dolerite (not

Fault) may be locus for volcanic eruptions. East-northeast-trending structures in northwest Northern Territory may be transform faults. Basalts are unmetamorphosed.

Geochemistry

province. Characterised by low-Ti, depleted High Field Strength Elements (HFSE) relative to other incompatible elements and marked enrichment in Th relative to U (Glass 2002, Glass et al 2006, Glass and Phillips 2006).

Correlation with other units: Geochemically similar

et al 2010). Mount Wright Volcanics and Cymbric Vale Formation (both Gnalta Group) of Gnalta Shelf, western New South Wales; Truro Volcanics of Stansbury Basin, South Australia – all biostratigraphically dated as late early Cambrian (Botomian stage of Siberia; Jago et al 1984, Jenkins and Hasenohr 1989, Gravestock 1995, Kruse and Shi in Brock et al 2000). Possibly Mooracoochie Volcanics (Gatehouse 1983), unconformable beneath middle Cambrian Kalladeina Formation of Warburton Basin, South Australia.

Commentsdominance of the igneous component relative to minor intercalated and underlying sedimentary rocks. Suite

formations, exclusive of any intercalated and immediately underlying, but associated sedimentary rocks. The latter are still included in constituent formations, but are excluded from suite; eg Malley Spring Member and Mount Close Chert Member (Mory and Beere 1985) are included in Antrim Plateau Volcanics; Muckaty Sandstone Member is included in Helen Springs Volcanics (Kruse in Hussey et al

Basalts, but Kalkarindji Suite has greater areal extent and is not as stratigraphically thick as the former. Volcanism is coincident with earliest known Phanerozoic mass extinction (Toyonian mass extinction; Glass and Phillips 2006).


Documents

Geology and mineral resources of the Northern Territory · 2019. 7. 3. · Australia, central Western Australia, northwestern South Australia and possibly areas of South East Asia