Geology & Geophysics of the Koonenberry Belt, Far Western New

Geology & geophysics of the Koonenberry Belt, far western New South Wales, and eastern Australian correlates:

Part II Delamerian Fold-Thrust Belts in eastern Australia

Nicholas G. Direen Clv ic-1-0(0-s B.Sc (Hons) (UTas)

A thesis submitted in fulfilment of the requirements of the degree of Doctor of Philosophy at the University of Tasmania, Hobart, Australia February 1999

198 PART 2: DELAMERIAN FOLD-THRUST BELTS IN EASTERN AUSTRALIA

Chapter 9: Fleurieu "Arc", South Australia 9.1 Adelaide Fold-Thrust Belt, Delamerian type area. Possible correlations with NSW 9.2 Truro Volcanics: structure, stratigraphy, tectonic affinity. Review. 9.3 Petrology & geochemistry 9.4 Relationship to Koonenberty Belt (MA V) 9.5 Kanmantoo Group: stratigraphy, structure, tectonic affinity. Review. 9.6 Sedimentology 9.7 Overall structural and magmatic style of the Adelaide Fold Belt. 199 Chapter 9: Fleurieu "Arc", South Australia

9.1 Adelaide Fold-Thrust Belt, Delamerian type area. Possible correlations with the Koonenberry Fold-Thrust Belt.

Part 1 of this study has shown that the Koonenberry Belt-Bancannia Trough region of far north-western New South Wales is a polydeformed fold and thrust belt which underwent major compressive tectonism during the Late Cambrian and again during the Silurian. The earlier of these two deformations has been correlated with the Delamerian Orogeny in South Australia, following the conclusions of Mills (1992) that these deformations are part of larger orogenic events. The Delamerian Orogeny is further correlated with the Tyennan Orogeny of Tasmania (Turner et al., 1998) and Ross Orogeny in Antarctica (Flottmann et al., 1993).

The Delamerian Orogeny was originally defined by Thompson (1969) as a Late Cambrian to Early Ordovician deformation, with several discrete "movements". Recent work in the Fleurieu Peninsula and southern Flinders Ranges has challenged many of the entrenched ideas about the structural development (Jenkins, 1990; Jenkins & Sandiford, 1992; Flottmann et al., 1994) and timing (Haines & Flottmann, 1998a) of the Delamerian Orogeny.

Haines & Flottmann (1998a) reviewed earlier chronological and geological evidence for the onset and duration of the Delamerian Orogeny. They interpreted the earliest indicator of deformation as the deposition of a foreland-basin red-bed package (the Billy Creek and Minlaton Formations) unconformably overlying the Hawker Group. The latter is considered to be an equivalent of the enigmatic Kanmantoo Group (see 9.5 below). SHRIMP zircon U-Pb dates from a tuff horizon within the red-bed package indicate an age of deposition of 522.8 ± 1.8 Ma. (ibid.).

The earliest assumed syntectonic intrusive recorded is a deformed granite from Vivonne Bay, Kangaroo Island, Rb-Sr dated at 523 ± 6 Ma (Preiss, 1995), but a more widely accepted date for the onset of deformation is the 516 ± 4 Ma SHRIMP U-Pb zircon date from the Rathjen Gneiss (Preiss, 1995). The Rathjen Gneiss is interpreted by most workers as a syn-tectonic granite, although recent evidence suggests that the gneiss protolith may have been a pre- or syn-tectonic sill complex or ignimbrite (A Burtt, pers. comm. 1998; Foden et al., unpublished data). The oldest, unarguable syn- tectonic granite is the Willoughby Granite from Kangaroo Island, SHRIMP U-Pb zircon dated at 508 ± 7 Ma (Haines & Flottmann, 1998a). This accords with SHRIMP dates 200 from syn-tectonic mafic dykes averaging 510 ± 2 Ma (Chen & Liu, 1996). The youngest SHRIMP date for a deformed granite is 487 ± 2 Ma from the Summerfield Granodiorite (Sandiford et al., 1992). Thus the Delamerian Orogeny may have commenced as far back as 525 Ma, and was definitely in progress from 508 to 487 Ma.

This overlaps with the 497.5 Ma to 492.5 Ma timeframe for Delamerian deformation in the Koonenberry Fold Belt (see Part 1). In addition to apparently synchronous timing of deformation, there seems to be broad tectonostratigraphic equivalence between packages in both belts. Previous workers have proposed lithostratigraphic correlations between the Mt Arrowsmith Volcanics and Truro Volcanics (Crawford et al., 1997), the Kara beds and the Normanville Group, and the Teltawongee Group and the Kanmantoo Group (Mills, 1992). The comparative simplified stratigraphic columns and the proposed correlations for both fold-belts are shown in Figure 9.1.1.

The studies below examine the characteristics and tectonic affinities of the proposed correlative packages, and also compares the overall structural and magmatic style of the Adelaide Fold-Thrust Belt with respect to the Koonenberry Fold Belt.

9.2 Truro Volcanics: structure, stratigraphy, tectonic affinity. Review.

In 1959 regional mapping by geologists of the South Australian Geological Survey in the Truro area, northern Mt Lofty Ranges (Figure 9.2.1), resulted in the description of some poorly exposed mafic to intermediate volcanics at Dutton. The exposures included altered andesitic and basaltic lavas, tuffs, agglomerates, and interbedded limestones. Subsequent investigators (Forbes & Daily, 1972) described the stratigraphy at the Dutton type section, naming them the Truro Volcanics. In the type section, the Truro Volcanics disconformably overlie calcareous rocks correlated with the Mt Terrible Formation of the Normanville Group on Fleurieu Peninsula, and are intimately associated with marbles and siltstones correlated with the Fork Tree Limestone of the Normanville Group. This association implies a subaqueous environment of eruption for these volcanics.

Later investigations in the region described new outcrops of tuffaceous andesitic volcanics interbedded with laminated shales at Accommodation Hill, Sedan Hill and Red Creek (Gatehouse et al., 1991a,b) and elsewhere (Cobb & Farrand, 1984) (Figure 9.5.1). The enclosing sedimentary sequence for these other occurrences has been correlated with the Heatherdale Shale (Gatehouse et al., 1991a), the formation above the Fork Tree Limestone on Fleurieu Peninsula (Abele & McGowran, 1959). Other

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King a Island Smithton Trough 0 500 km raLaLs 201 mafic volcanics at nearby Mame River (Mills, 1973) were found to be rift tholeiites similar to those found in the Smithton Trough in northwestern Tasmania (Van der Stelt, 1990; and see Chapter 11).

The first geochemical analysis of the Truro Volcanics was undertaken by Van der SteIt (1990). This indicated that the Truro Volcanics were transitional tholeiitic to alkaline andesites, trachyandesites, basalts and trachybasalts. Further analyses were undertaken by Gatehouse et al. (1991b), confirming these affinities for samples drilled in Mt Rufus-1, a stratigraphic drillhole in the Karinya Syncline. Mafic volcanics and interbedded carbonates intersected in stratigraphic drillhole Peebinga-1, some 180 km to the east-southeast (Figure 9.2.1) were correlated with the Truro Volcanics (Rankin et al., 1991) on the basis of similar geochemistry and an association with shale and limestone.

The mafic-intermediate lavas in the Truro Volc,anics have never been directly dated. Assumed, indirect evidence for their age comes from Early Cambrian archaeocyathan ages for the Fork Tree Limestone and ?middle Early Cambrian trilobites from the Heatherdale Shale, all on Fleurieu Peninsula (Jago et al., 1984). Cooper et al. (1992) dated a felsic tuff layer from the Heatherdale Shale from the Fleurieu Peninsula using the single crystal SHRIMP zircon U-Pb method. They reported an age of 526 ± 4 Ma, which is early-mid Botomian (Early Cambrian) (Shergold, 1995), agreeing with fossil evidence. It is unclear how this tuff came to be correlated with the Truro Volcanics, as no felsic units have been previously reported from the sequence, and Cooper et al. (1992) made no such correlation. This error may have arisen as a result of an oversimplified stratigraphic column in Gatehouse et al. (1992). Veevers et al. (1997) paper also assumes this inaccurate correlation.

On the basis of their similar distinctive immobile trace element and isotopic geochemistry, Crawford et al. (1997) postulated a correlation between the Truro Volcanics and the Mount Arrowsmith Volcanics. This gives rise to a conflict in apparent ages of the two units: 587 ± 8 Ma for the MAV (Crawford et al., 1997), 526 ±4 Ma for the Truro Volcanics. In noting this apparent conflict, Crawford et al. (1997) questioned the validity of the regional correlations that give rise to the assumed age of the Truro Volcanics and speculated that the Truro Volcanics might in fact be as old as the MAV. This is theoretically possible, as all the supposed age inferences for the Truro Volcanics comes from the Fleurieu Peninsula, some 150 km south of the type section, where there are no known mafic volcanics. In addition, the original lithostratigraphic 202 correlation is made across a strongly folded and thrust faulted terrane (e.g. Flottmann et al., 1994).

However, the value of Crawford et al.'s (1997) speculative correlation is limited due to the small sample size (3 samples) and limited spatial sampling (Red Creek locality only) used for the Truro Volcanics in their study.

The study outlined below aims to compare an expanded data set for the Truro Volcanics compiled from unpublished data, together with new samples from the type section, and unpublished data used by Crawford et al. (1997). In addition, the correlation between the Truro Volcanics and those intersected in the Peebinga-1 drillhole is investigated in detail.

9.3 Petrology & Geochemistry

The primary sources of data for the study below are gleaned from literature housed in the collections of the University of Adelaide and Primary Industries and Resources South Australia (PIRSA). All of this data is unpublished at the time of writing. Specifically, data for Stun Highway, Accommodation Hill and Red Creek are from Van der Stelt (1990). Mt Rufus-1 data are from Gatehouse et al. (1991b), and data for Peebinga-1 are from Rankin et al. (1991). These analyses are combined with data from Red Creek obtained by Crawford et al. (unpublished data), and from Dutton (this study).

Several samples of andesite and andesitic tuff were sampled by the author at Dutton in May 1997. These were added to three samples collected at Red Creek by B. Stevens, referenced in Crawford et al. (1997). Thin-sections for all these rocks were prepared and petrographically examined.

The Dutton samples are all metamorphosed to lower greenschist facies, but retain relict primary phenocryst assemblages and textures. Three samples are sparsely cpx- phyric basaltic lavas, with up to 10 modal percent relict cpx phenocrysts or glomeroporphyritic domains. These are epi-chl altered. The groundmass consists of highly altered plagioclase with chl-epi-hm alteration, and makes up 85 to 90 modal percent of these rocks. The presence of haematite may be indicative of altered primary magnetite phenocrysts. Sample 9723 is a volcaniclastic siltstone with components of volcanic quartz, glass shards and altered glass. 203 Samples from Red Creek are abundantly blocky plag-phyric andesite lavas with minor cpx. Plag is shot through with sericite alteration, but cpx appears unaltered. The largely interstitial groundmass of finer plagioclase is altered to ser-epi-chl; minor qz is also found A chl-bio domain in one sample (RC3) may be a contact metamorphosed rip-up clast of sediment.

From the 7 Dutton samples (6 lavas, 1 volcaniclastic), two basalts and two andesites were chosen for XRF major and trace element analysis according to the procedures described earlier in this thesis (e.g. Chapter 4.9). The new data are listed in Table 9.3.1. Major and trace element diagrams are shown (Figures 9.3.1), along with immobile element plots and ratio diagrams (Figure 9.3.2). The diagrams include unpublished analyses for the Truro Volcanics and the data from this study. Also plotted are two analyses from the Peebinga-1 drillhole, taken from Rankin et al. (1991). A field for the MAV is from Crawford et al. (1997).

The samples from this study, especially the two from Dutton (Table 9.3.1), have very low Si02 and high LOI values, indicating intense alteration. This is borne out by pervasive chl-epi in these glassy lavas. Samples from Red Creek, and other Truro samples are all alkaline basalts, displaying high P205, Ti02, Zr and Nb at 50% Si02; these affinities are confirmed by the tectonic discrimination diagrams (Figure 9.3.2).

The within-plate character of these rocks is further demonstrated in Figure 9.3.2. Zr/Nb ratios, maintaining a constant value at all levels of fractionation (in this instance, represented by the immobile Ti), are very source specific. For example Zr/Nb for E- MORB is typically 12-30, and for N-MORB, >30; values of < 10, as observed in the Truro and MAV samples, are typical of WPB (Deniel et al., 1994).

Truro and MAV also form a transitional array between N-MORB and 016 values in plots of Y v Zr, indicating an enriched mantle source observed in young rifts (e.g. Afar Rift, Deniel et al., 1994)

Figure 9.3.3 shows N-MORB normalised spidergrams for the range of Truro Volcanics sampled. The patterns show strong LILE enrichment, characteristic of alkali magmas (Sun & McDonough, 1989). Figure 9.3.4 shows a median Peebinga basalt plotted together with the range for Truro samples; the similarity in pattern is obvious, supporting the correlation of these two suites. Figure 9.3.5 plots a more limited array of immobile elements for Truro, Peebinga and the Murteree-Jena basalt samples from the Warburton Basin. The latter units are also correlated with the MAV (see chapter 5).

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Figure 9.3.1 Oxide/element variation diagrams, Truro Volcanics Field from Crawford et al. (1997). x = this study; diamond = Truro; squares = Peebinga **Note trace elements not measured for Red Creek samples, this study Dutton Red Creek Sample 9720 9721 RC1 RC3 RC3A Rock basalt basalt andesite andesite andesite Si02 41.89 42.73 55.00 48.24 48.02 TiO2 3.03 2.73 2.38 2.54 2.40 Al203 15.09 14.19 19.42 18.63 17.17 Fe203 13.33 14.42 10.81 11.08 8.30 FeO* 11.99 12.97 9.73 9.97 7.47 MnO 0.19 0.18 0.04 0.19 0.35 MgO 15.53 13.19 2.76 3.65 3.22 CaO 7.44 8.37 1.78 6.60 11.71 Na20 1.94 2.08 5.33 5.86 5.97 K20 0.47 1.13 1.36 2.46 2.12 P205 1.09 0.98 1.13 0.74 0.73 LOI 6.05 4.66 2.96 8.20 12.68

Ni 242 255 N/A N/A N/A Cr 493 484 V 304 426 Sc 32 33 Zr 264 236 Nb 96 85 Y 30 30 Sr 392 726 Rb 12 26 Ba 228 621 Pb 3 5 Th 5 3 La 48 58 Ce 99 116 Nd 45 49 Ti 18153 16378

NbN 3.21 2.78 Zrfri 0.01 0.01

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Figure 9.3.2 Trace element discrimination diagrams, Truro Volcanics Key & MAV field as for Fig.9.3.2; 01B and NMORB arrays from Sun & McDonough (1989)

Figure 9.3.3 N-MORB normalised spidergram, Truro Volcanics (normalising data from Sun & McDonough, 1989) Figure 9.3.4 N-MORB normalised spidergram Peebinga-1 Peebinga data from Rankin et al. (1991)

Figure 9.3.5 N-MORB normalised spidergram Peebinga, Truro Volcanics and Murteree-Jena Volcanics (Warburton Basin)

(normalising data from Sun & McDonough, 1989) Murteree-Jena data from Sun (1996) 204 Again, strong LILE enrichment is evident, suggesting all three suites were derived from an enriched MORB source which experienced crustal contamination during rifting. Slight discordances are probably attributable to bulk mantle inhomogeneity over the 69000 km2 area represented by these samples. Boucher (1994) also proposed correlations between the Murteree-Jena Volcanics of the Warburton Basin (see Chapter 5.6), Peebinga-1 and Truro Volcanics, although he proposed a Cambrian age; because of the correlation of these rocks with the MAV, a Late Neoproterozoic age of rifting is more likely (see below).

9.4 Relationship of the Truro Volcanics (and correlatives) to the Koonenberry Belt

The Truro Volcanics are a mafic to intermediate suite of lavas and interbedded volcaniclastics which crop out in the Karinya Syncline region of the Adelaide Fold-and- Thrust Belt. Conventional regional lithostratigraphic correlation has placed the Truro Volcanics at several horizons within the Early Cambrian Fork Tree Limestone and Heatherdale Shale formations within the Normanville Group. Conventional wisdom (e.g. Cooper et al., 1992; W. Preiss, pers. comm.1998) suggests that a felsic tuff with a zircon age of 526 ± 4 Ma from a section away from the type area supports this correlation. Geochemical data from the Truro Volcanics and previously suggested correlatives, Peebinga-1 Volcanics and Murteree-Jena Volcanics, show transitional tholeiitic to strongly alkaline characteristics, and strong crustal signatures indicating a within-plate continental setting for eruption. Their association with interbedded subaqueous sediments such as limestone and shale is strongly suggestive of a rifted- margin environment (e.g. Veevers & Cotterill, 1978), although a lacustrine-influenced internal rift valley (e.g. East African rift system) may also be a possibility.

Crawford et al.'s (1997) suggestion that the Truro Volcanics (and correlatives) might be the equivalent of the Mt Arrowsmith Volcanics from the Koonenberry Fold Belt is not ruled out by the analysis of a more extensive dataset for the Truro Volcanics and related rocks. Both groups show similar geochemical traits, and more importantly, bear evidence of having been contaminated by continental crust with similar bulk chemistry, and probably of equivalent age.

At least two alternative scenarios could be invoked to explain these facts: 1. Crawford et al. (1997) are correct. This implies a wider distribution of rifting at c.590 Ma than previously recognised, with sites in northern, central and eastern South Australia, plus sites in NSW, being involved. The geometry of magnetic anomalies Figure 9.4.1 Form of magnetic anomalies in eastern South Australia

138° 140° 142° 144° 205 associated with these volcanics (Figure 9.4.1) suggest a string of compartmentalised rifts along the southeast Australian lineament system, rather than en echelon, parallel or failed arm-type geometries. In this case, the felsic tuff in the Heatherdale Shale may represent secondary (backarc?) rifting at c. 525 Ma as proposed by Crawford et al. (1997) (and see Chapter 5). The proximity of the Truro Volcanics to likely Kanmantoo Group equivalents in Red Creek (Gatehouse et al., 1991a) can be explained by unrecognised thrust faults, present in other parts of the Adelaide Fold Belt (Jenkins, 1990; Flottmann et al., 1994). A likely place for a fault is the phyllite horizon with "boudinage" occurring between the top pillow basalt of the Truro Volcanics and the sandstone-mudstone couplets correlated with the Kanmantoo Group at 212 m above the base of the Red Creek measured section (Gatehouse et al., 1991a Fig 4c). The likelihood of this type of "bed" being a phyllonite/mylonite zone was noted by Jenkins (1990). A second fault may be present at 266 m if "quartz veins" recorded are cataclasite, a common feature marking thrusts in sandy lithologies (Cayley & Taylor, 1997, Figs. 71 & 72). Common ages for the two volcanic packages could be tested by palaeomagnetic means: basalts erupted at similar times may preserve the same remanent field vector, whereas for basalts separated by 65 Ma, this would be unlikely. 2. The MAV and Truro-Peebinga-Murteree-Jena volcanic suites represent two separate phases of rifting. Similar Nd isotopic signatures (see Crawford et al., 1997) could be possible if the 525 Ma rift event sampled/partially remelted a stagnant underplate of the earlier 590 Ma rift event. Again, a palaeomagnetic test could support this hypothesis, as two separate bodies with different ages would be expected to have differing palaeomagnetic vectors.

The testing of these hypotheses using palaeomagnetics or extensive reconnaissance mapping is beyond the scope of this study, but could be achieved with relative ease. The current balance of evidence appears to favour the first hypothesis, suggesting a closer affinity between the Koonenberry Fold Belt and the outboard part of the Adelaide Fold Belt than previously suspected.

9.5 Kanmantoo Group: stratigraphy, structure, tectonic affinity. Review.

In his 1992 paper, Mills postulated a lithological correlation between the "Teltawongee beds" and the base of the Kanmantoo Group of the Adelaide Fold Belt. In particular, he considered that the base of the Nundora Formation shows "close lithological similarity to the contact between the Carrickalinga Head Formation.., and the Heatherdale Shale (top of the Early Cambrian Normanville Group)" at a location north-east of 206 Carrickalinga Head. The two localities are separated by approximately 600 km. Are there enough similarities between these two formations to warrant correlation of the Kanmantoo and Teltawongee Groups? This question is addressed in the following discussion.

The Kanmantoo Group was originally erected by Sprigg & Campana (1953). Subsequent revisions to the stratigraphy were made by Daily & Milnes (1971; 1972; 1973), Gatehouse et al. (1990), Jago et al. (1994) and Dyson et al. (1996). The currently accepted stratigraphy is essentially that of Daily & Milnes (1973) (Figure 9.5.2). Gatehouse et al. (1990) summarised the stratigraphic history of the Carrickalinga Head Formation.

The Kanmantoo Group consists of various formations of medium- to fine-grained clastic rocks with minor conglomerate and carbonate horizons. In the lower parts of the stratigraphy (Carrickalinga Head Formation), these are turbiditic, but the upper parts of the stratigraphy contain abundant evidence of deposition by tractional currents in shallower waters.

All formations were variably metamorphosed between greenschist facies up to sillimanite or migmatite grade during the Delamerian Orogeny (Jenkins & Sandiford, 1992). Until recently, traditional methods of retrodeformation predicted that the thickness of the Kanmantoo Group sedimentary section was around 18 000 m (I) (Gatehouse et al., 1990). However, recent workers, recognising thrust faults (Jenkins, 1990; Jenkins & Sandiford, 1992) and using section-balancing techniques (Flottmann et al., 1994) have shown major fault repetitions of the stratigraphy, and calculated a reduced thickness of c. 8000 m.

The proposed origin of the Kanmantoo Group is contentious. The original model (Daily & Milnes, 1971, 1972, 1973) suggested that the sediment was derived locally from uplifted horst blocks, and deposited in relatively shallow water by tractional currents. Von der Borch (1980) interpreted the sequence as representing a passive margin clastic wedge, with deep-water basinal facies on Fleurieu Peninsula, and shallower shelf facies to the north. Jenkins (1990) suggested that at least some of the Kanmantoo Group was allochthonous. This idea was further developed by Flottmann et al. (1994) who showed that thrusts inverted Early Cambrian down-to-the-east extensional growth faults. These early faults were interpreted to have formed an inboard marginal basin (the Kanmantoo Trough), relative to a continental shelf and slope represented by the correlative Glenelg Complex of western Victoria (Gibson & • Moonta AuStraho toms Rivet ton Pori Wakefield

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FLEURIEU PENINSULA KARINYA SYNCLINE SOUTH COAST

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*modified after Gatehouse et al., 1992 207 Nihill, 1992; Tumer et al., 1993). An alternative interpretation, first mooted by Jenkins (1990), is that the Kanmantoo Group represents a flexural foreland basin to the westward-advancing Delamerian orogenic front.

Objections to a foreland-basin origin for the Kanmantoo Group were raised by Powell et al. (1994). These include the bulk cratonic derivation of the Kanmantoo sediments (Jenkins, 1990; Ireland et al., 1998), and the syn-sedimentary growth faults identified by Flottmann et al. (1994), both of which are unlikely in a foreland setting.

In summary, the tectonic setting and timing of the Kanmantoo Group are contentious. The proposed correlation of Mills (1992) between the Carrickalinga Head Formation and rocks now belonging to the Nundora Formation must be examined in this light.

9.6 Sedimentology of the Madigan Inlet Member, Carrickalinga Head Formation 9.6.1 Introduction

To facilitate fair comparison of the two sections, fieldwork was conducted at the location mentioned by Mills (1992), and an equivalent sedimentological dataset to that described at Chapter 4.6 compiled. This is described in the sections below.

9.6.2 Physical Sedimentology

Type section: The type section for the base of the Carrickalinga Head Formation was established by Gatehouse et al. (1994) in the location described by Mills (1992) (257724 mE 6078687 mN AMG Zone 54). A lithological log is shown in Figure 9.6.1.

Thickness: the dip corrected thickness of the type section is 78 m (C. Gatehouse, pers. comm., 1997). Gatehouse et al. (1994) reported 80 m. This is named the Madigan Inlet Member. A reference section for the entire Carrickalinga Head Formation at Sedan Hill (see Figure 9.5.1) is 1700 m thick, with only the basal few metres of the Madigan Inlet Member missing (Gatehouse et al., 1994).

Rock types: these are reviewed principally in Farrand (1990) and Gatehouse et al. (1994). These studies did not use the classification scheme of Folk et al. (1970), and did not report percentage components. Rocks described, in order of abundance, include micaceous feldspathic sandstones, feldspathic sandstones, and lithic sandstones. Gatehouse (1988) called these rocks medium to fine-grained quartz arenites. Petrographic analysis of samples collected by the author revealed (in order of

Stratigraphic log, base Carrickalinga Head Formation

Remarks: (Madigan Inlet Member) 257724 mE 6078687 mN AMG zone 54 S31

GRAIN SIZE :1 N 11 1IIT

I HLS1Y3ISAH S3DIOSSMOV pebble granule sand 1 I i v I rho v d

REMARKS iirli 2 Y-1 , 1 , 1 I

• • • • • • • • • .

......

.42

. 411 ! .. • • • • • • •

...... ) ...... • . .. ". ". . •. ." . •. .• ...... ' .• .' .• . ' 38. . • • ......

:•...•:•.•.•••.•.•: 36

. •:•:•:•.•.•.•: —V 4 +)—

••• :.• . . ::::::•. . —X + W

2 —V , . • ......

... ::::...•.•.• . . . . . —U . • . • . • .• • .•. —T .30 ...... ---s . ' . '.'. ' • • —R . :::::• —o

•28 . •...... •...... •

. . . :::: • ...... P

. • . •:.••• • • 4 •26 -0 —Sample for detrital monazite dating . • . •.• .•.•.•.•.•.•. (see text) ...... • -

. • ...... •.*:•.•. 0

--0 24 1 .. . . —N

,..1.4 22. I , . •...... ! . . . . .•.•...... •••••••••••••.• • ...... —L •• • • . • . . .20.

• . ----..K

;- —.) ...... 7...... :::::•:. 18 I ! . . . • —1 • • • j . •••••••'...' —H

•16 —:

.. —F •14 .. • • • • .. • •

... . . —E

.., D — _.... — — .— _ ' . I \-C ... • • • • • . : . :• : • . . • . • -••%,-A .., • i ....,

.10. ::•:::-..-..-..-..••..-..-..1......

:: . :::::::•.•:::::* ...... ■ Base Kanmantoo . .•.•.•.•.•.•.•.•• . Group .. • " • • • • • '

...,•••:.•7_•••., .7.,:' • 'C.- -...... wTop Normanville Group -, --...... "7.- ---: :•.' • .:.''.: :•• -='7: :---••*- 4 -1— • • •-.:.:.:.-.)-.).- :35553535_ r -p_r_r_:::::,:r:r:

3:::: .45- D ;::::::::::::::::::),:: •...., ::IC'P 1. r -o• -• •" r_r_r:r -r:r:P:r -r: r 1P• j; j:ilit43 - 0

;4":14444:4 - 1003:::;:;i:1::

rP :':. 4 :; :; :: :: :: :

LEGEND

LITHOLOGY

Inil SANDSTONE 888 SILTSTONE ili: SHALE kikk Phosphatic ehale

CONTACTS

./.....**.ov Scoured ww...... Gradational -...... ---•-• Undulating

PHYSICAL STRUCTURES

JR,R. climbing current ripple ,.. parallel lamination c=s parallel wavy lamination

..;=, Rip-up Claate I • Water escape pipes ...... ". scour

Figure 9.6.1 208 abundance) micaceous lithic arkose, feldsarenite (or arkose), litharenite, dolomitic arenite and quartz arenite. Feldspars include plagioclase, K-feldspar and microcline, and micas are predominantly white (sericite, muscovite) although detrital biotite is also found. Lithic components are usually shale, and may be rip-up clasts.

Geometry: All beds investigated have sheet geometries that are traceable in three dimensions for tens to hundreds of metres, limited by outcrop conditions.

Contacts: The basal contact of the Madigan Inlet Member with the underlying Normanville Group is scoured and either a disconformity or angular unconformity at some locations (Jago et al., 1994). The disconformity is represented in the type section by an erosive base with lag gravel clasts. Nearby, there is an angular bedding discordance of 11 0, attributed to rotation on extensional fault blocks (ibid).

The top of the Madigan Inlet Member is described in the reference section at Sedan Hill, where it is 850 m thick (Gatehouse et al., 1990). It passes conformably up into the Blowhole Creek Siltstone Member, a 450 m thick laminated phyllite package. This passes sharply up into the c.135 m thick Campana Creek Member, a package of cross-bedded fine to medium sandstones (Gatehouse et al., 1990)

Bedding: thick to very thick massive sandstone beds 0.5 to 5 m, averaging lm but generally thickening upwards. Fine laminations (2-3 mm) are rarely developed. Shale beds are mostly finely laminated and often show phyllitic cleavage development. However, some shale beds may be thickly laminated to thinly bedded (1-4 cm layering).

Sedimentary structures: water escape pipes, climbing ripples, wavy bedding and chaotic bedding are all found in this section. Normal "grading" occurs, although this takes the form of a fairly abrupt change in modal grainsize usually over 1-2 cm, rather than the continuous decrease in grain size usually found in normally-graded sediment. This feature was also commented on by Gatehouse et al. (1990). Several beds contain elongate (up to 10 cm) rip-up clasts of mudstone, possibly derived by scouring out intervening shale beds; amalgamated sand beds produced by this mechanism are common throughout the section.

Petrographic texture: Farrand (1990) described thirty-eight thin sections from various horizons within the Carrickalinga Head Formation at locations throughout the Fleurieu Peninsula. He found this collection to be poorly sorted with angular clasts ranging in 209 size from 0.05 to 0.5 mm, and with very few grains larger than 0.5 mm. These sizes class them as fine- to very fine -grained sandstones. Matrix is abundant, and formed from micaceous minerals. In general, he found no systematic relationships between bedding and the grain-matrix compositions, grain size, grain origin, QFL compositions, accessory mineral components, or colour.

Heavy mineral assemblage: Farrand (1990) reported zircon, tourmaline, sphene, opaques and garnet in varying abundances from throughout the Carrickalinga Head Formation. In the present study, crushing and separation of heavy minerals using the techniques described at 4.6.3 revealed garnet, chromite, zircon, monazite, rutile and pyrite. Electron microprobing of the gamets shows almandine compositions (Table 9.6.1) indicating probable derivation from amphibolite or granulite metamorphic sources. The nearest feasible source for such clasts is the Gawler Craton to the west, but this has been ruled out as a sediment source by the work of Ireland et al. (1998) (see below).

Table 9.6.1 Average Garnet Composition, Madigan Inlet Member

Mg0 (wt%) Al203 Si02 (wt%) CaO (wt%) FeO* (wt%) (wt%)

Average 8 22 38 2 30 garnet

Electron microprobe analyses of chromite shows a (small) population with high Cr# and very low Ti02; these features are typical of chromite grains derived from boninitic sources (Figure 9.6.2). Of course, such a small sample set should not be used to infer tectonic relations. However, the presence of boninitic arc-derived spinels in what is essentially a craton-derived sedimentary pile (Daily & Milnes, 1973; Powell et al., 1994; Ireland et al., 1998), is intriguing, and warrants further investigation beyond the scope of this study.

Geophysical logging: As with the Nundora Formation, the basal section of the Madigan Inlet Member was logged using a gamma ray spectrometer. Data were acquired at 50 cm intervals using the window of interest method from 8 m beneath the datum to 30 m above. The same instrument, acquisition procedure and processing were applied to these data as listed in Chapter 4.9.3. Data are displayed in two figures, 9.6.3 & 9.6.4. The bimodal character is due to changes in the concentration of potassium in silty-shaly units (high concentrations) relative to sandy units (low concentrations).

70 —

60 —

50 —

V 30 — c.) Boninites (New Caledonia & Hunter Ridge)

20 —

10 —

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 TiO2 (wt%)

Figure 9.6.2 Discrimination diagram for Detrital chromite analyses from the Madigan Inlet Member, Carrickalinga Head Formation

Boninite field is from Crawford (unpublished data) -

Fig ure 9.6.3 Full 256 Gamma Ray spectrum, Madigan Inlet Member, Carriekarma Head, SA

G2PP2E288!-'*422 Z Channel

Fig ure 9.6.4 Gamma ray spectrometry across the basal Madigan Inlet Member

g25

gt. -4—Total Count

76-1.1 E —X—K

Et 15

10 15 30 Distance (m) 210 Age: Problems with the age of the Kanmantoo Group are summarised by Haines & Flottmann (1998a). Currently, the best age constraints are from the tuff horizon in the Heatherdale Shale and the age of the syn-tectonic Rathjen Gneiss. These indirect dates constrain the depositional age of the Kanmantoo Group between 526 ± 4 and 516 ± 4 Ma. On current thickness estimates for the Kanmantoo Group of c.8km (Haines et al., 1996), these ages imply average sedimentation rates between 0.4 and 4 mm/year.

9.6.3 Facies Interpretation

Daily & Milnes (1973) outlined evidence to suggest that the Kanmantoo Group was deposited in a rapidly-subsiding, fault-controlled sub-aqueous basin. They also argued that the Group, while having some graded bedding and other features associated with turbidites, was not, as a whole, representative of a turbidite package. The upper formations of the Group, including the Backstairs Passage, Tappanappa, Balquhidder, Petrel Cove and Middleton Formations, contain an abundance of sedimentary features produced by tractional currents. Von der Borch (1980) interpreted the Carrickalinga Head Formation as a turbidite package, based on its turbidite-like features, but later authors (Gatehouse et al., 1990; Jago et al., 1994) interpreted the Madigan Inlet Member as a sediment gravity flow deposit on a low-stand submarine fan. This interpretation was integrated into a sequence stratigraphic model which further interpreted the Blowhole Creek Siltstone Member as a transgressive systems tract, and the Campana Creek Member and Backstairs Passage Formation as a highstand systems tract. These sequence stratigraphic terms imply deposition in an open marine basin subject to eustatic mechanisms, such as a continental shelf or marginal sea basin, rather than an internal trough. More recent authors (Haines et al., 1996; Haines & Flottmann, 1998a) have also supported a sediment gravity flow origin for the more turbidite-like members, and tidal or contour current reworking for the members with tractional affinities.

Features observed in this study to support a mass-flow origin for the Madigan Inlet Member include: • rip-up clasts of underlying beds, produced during high flow regimes; • amalgamated sand beds, produced by flows scouring out intervening hemipelagic mud; massive sand beds, produced from a single flow event; • lack of true continuous normal grading, suggesting rapid pulses of sediment input rather than a waning turbidity current flow; 211 • climbing ripples, indicating simultaneous deposition and transport of bedload; • chaotic beds and slumping, indicating unstable depositional environments; and dewatering structures such as pipes, indicating fluid escape after rapid deposition of sand in liquefied slurries.

In addition to these features, the chemical and physical immaturity of the clasts, and matrix-rich nature of these rocks suggest rapid deposition without protracted sorting. Gatehouse et al. (1990) proposed two models to explain these features: deltas feeding directly onto submarine fans during a period of lowstand; or mass-slumping from the continental shelf of deltaic material during a period of active tectonism. Given a lack of visible incision (in the form of canyons) into the underlying Heatherdale Shale (cf. Jago et al., 1994), and the occurrence of listric growth faults throughout the Kanmantoo Group (Flottmann et al., 1994), the second hypothesis must be preferred.

9.6.4 Provenance

Monazites separated from a massive sandstone bed with rip-up clasts and high Th character in the gamma ray log (bed P), were dated using a new experimental electron microprobe technique developed after Montel et al. (1996) (Meffre & Berry, in prep). This involves the use of the Th-Pb isotopic system, and is able to provide dates with a standard deviation error of about 15 Ma (S. Meffre, pers. comm., 1998). Some 15 analyses on 12 grains from bed P form an isochron with an age of 606 Ma (Figure 9.6.5a: Direen & Meffre, unpublished data).

Ireland et al. (1998) presented detrital zircon SHRIMP U-Pb data for a sample from the Carrickalinga Head Formation. Based on a sample of 100 grains, they showed a main peak at 500-700 Ma, with subsidiary peaks at 900-1200 Ma and 1500-3500 Ma. These peaks were also found to be repeated in the Balquhidder Formation, and have been associated with "Ross-Delamerian", "Grenvillian" and Proterozoic source terranes. These data are significant because they indicate that, contrary to previous assumptions (cf. Daily & Milnes, 1973), the Kanmantoo Group is not the product of simple erosional reworking of the Adelaidean sequence or crystalline basement of the Gawler Craton to the west. These sources have a range of peaks from 2100-2700 Ma, 1550-1900 Ma, 1000-1200 Ma, which are predominantly Proterozoic or Archaean. While local sources on the Yorke Peninsula are demanded by carbonate-bearing imbricate pebble conglomerates with westerly current directions (Jenkins, 1990), Haines et al. (1996) identified a southerly current direction in sandstones. This may be used to infer that the "Ross-Delamerian" and "Grenvillian" components in the 212 Kanmantoo Group were derived from an Antarctic source (Haines & Flottmann, 1998b).

A relative probability histogram of monazite dates from this study shows a discrete peak at c.580 Ma (Figure 9.6.6: Direen & Meffre, unpublished data) which overlaps that derived from the biggest peak in the zircon data of Ireland et al. (1998), providing independent verification of the provenance. The 580 Ma age is the age of crystallisation of the monazite crystals, and reflects the metamorphic age of either a high grade metamorphic source, or the crystallisation age of granite enriched in LREE (S. Meffre, pers. comm. 1998). The association with zircons of the same age tends to support the latter hypothesis. However, no study has ever reported granites from within the Late Proterozoic Adelaidean sequences (cf. von der Borch, 1980; Jenkins, 1990; Preiss, 1990; Powell et al., 1994). This reinforces the possibility of derivation of material from elsewhere, in particular Antarctica, as suggested by Ireland et al. (1998).

9.6.5 Comparison of the Nundora Formation and the Carrickalinga Head Formation

Despite the superficial similarity in the style of their basal stratigraphic contacts, and similar assumed ?Early Cambrian ages, it is unlikely that the Nundora Formation and the Carrickalinga Head are equivalent formations as suggested by Mills (1992). The Nundora Formation is best interpreted as a channel-levee complex deposited by turbidity currents in a deep basinal environment. Evidence to support this interpretation includes: • the degree of sorting; • wedge and channelled bedding geometries; • scoured contacts; development and thickness of bedding; • and the systematic variation of some clastic components with bedding. Other formations within the Teltawongee Group also reflect deposition in various turbidite fan environments.

This contrasts with the Carrickalinga Head Formation, which is interpreted to have been deposited as a series of sediment slumps in a rapidly subsiding fault basin. Evidence supporting this interpretation includes: • the lack of sorting and lack of systematic relationships between clasts and bedding; the immaturity of the clasts and rock-matrix continuum; • lack of bedding, amalgamated sand sheets and abundance of rip-clasts of hemipelagic mud; Figure 9.6.5 Isochron for U-Pb determinations on detrital monazites with electron microprobe

2800

2400

2000 1/1 slgmai:j •\ellipses

0. 1600 0.

0- 1200

800

y = 0.026x + 3.1543 580 400 Ma Isochron

I i • 1'1' I 0 20000 40000 60000 80000 100000 120000 140000 Th* (ppm)

Figure 9.6.6 Relative probability plot for U-Pb determinations on detrital monazites

0 200 300 400 500 600 700 800 900 1000 Age (Ma)

*all data from Meffre & Direen, unpublished dataset 213

• variable angular discordance at the basal contact, suggesting normal fault control and an overall extensional environment; • and features commonly associated with rapidly deposited slurries of material, including fluid escape structures, slump folds, and climbing ripples. Formations higher in the stratigraphy show a variety of tractional features associated with shallower water conditions.

As well as representing two different tectonic environments, the two formations also have been derived from quite different sources. The main source terrain for the Nundora Formation is probably the Cumamona Craton to its south and west, as indicated by palaeocurrents, and abundance of heavy minerals reflecting a high grade metamorphic terrain. The main age component of this sediment is dated at 1200 Ma, with subsidiary "Grenvillian" and Archaean sources (Stevens & Fanning, unpublished data). All of these are cratonic in nature. The Carrickalinga Head Formation, on the other hand, is principally sourced from the growing Ross-Delamerian orogen, with the main component dated at 600 Ma, and minor "Grenvillian", Proterozoic and Archaean input. Input from an orogenic source may also account for the tantalising glimpse of apparently arc-derived detritus, common in orogens the world over. These features have led some workers to postulate an Antarctic source for the Kanmantoo sediment.

In conclusion, the two formations represent quite different tectonic environments, with different sources. If truly age equivalent, it is possible that the Kanmantoo Group represents an inboard marine basin (as proposed by Flottmann et al., 1994) in a broad continental margin, with the Teltawongee Group representing a true continental slope environment on a narrower sector of the same margin. In this case, correlates of the Teltawongee Group might be found further outboard of the Adelaide Fold Belt, for example in the Glenelg Metamorphic Complex.

9.7 The Delamerian Orogen: tectonic style

The suggestion that deformed rocks in northwestern New South Wales might be part of the same orogenic province as those in the Adelaide Fold Belt found its first expression in Packham's (1969) "Northwestern Fold Belt". This included the Torrowangee beds (the Adelaidean equivalents of the Euriowie Inner), the "Wonominta Block", Mt Arrowsmith sequences and the various Cambrian sequences around Gnalta-Cymbric Vale (see Chapter 5). This idea was taken up in modified form by Scheibner (1972) in his "Kanmantoo pre-cratonic province", which was deformed in the Delamerian to form the "Kanmantoo Fold Belt". This fold belt was believed to 214 incorporate the Kanmantoo Trough of SA, Lower-Middle Cambrian rocks in northwestern NSW, and the Cambrian ophiolitic rocks of the Heathcote belt in Victoria. Scheibner (1972) linked this fold belt with the Tyennan and Adelaide Fold Belts. Griffiths (1971, 1974) had already suggested correlation of the Adelaide and Ross Fold Belts.

Correlations between the internal parts of the Adelaide Fold Belt and the Wilson Terrane in the Ross Fold Belt, and between the Glenelg Complex-Stavely Belt/Stawell Terrane and the Bowers Terrane have been substantiated by more recent work (Stump et al., 1986; Flottmann et al., 1993a,b; Flottmann & Oliver, 1994; Flottmann et al., 1994), leading to the idea of a contiguous Ross-Delamerian Orogen (Flottmann et al., 1993a). It is the structural and metamorphic style of the various parts of this orogenic belt that are examined below, with a view to determining the place of the Koonenberry Fold Thrust Belt (FTB) within the larger system.

Both the Adelaide Fold Belt and the Ross Fold Belt in Victoria Land retain evidence of thick-skinned thrusting (i.e. basement involvement), "hot" thrust stacks, syn- and post- deformation granitoid intrusion in the Middle Cambrian-Early Ordovician period, and associated high temperature-low pressure "Buchan-style" metamorphism. (Adelaide Fold Belt: Jenkins, 1990; Foden et al., 1990; Mancktelow, 1990; Jenkins & Sandiford, 1992; Gibson & Nihill, 1992; Flottmann et al., 1994. Victoria Land: Gibson, 1987; Flottmann & Kleinschmidt, 1991; Flottmann et al., 1993a, b; Flottmann & Oliver, 1994). Both belts appear to be large, divergent-thrust bounded "pop-ups": the AFB bounded by the east-dipping Talisker Fault (Flottmann et al. 1994) and west-dipping Glenelg- Yarramyljup Shear Zone (Flottmann et al., 1993b); and the Wilson Terrane bounded by the east-dipping Exiles Thrust (Flottmann & Kleinschmidt, 1991) and the west- dipping Lanterman Fault Zone (Gibson & Wright, 1985). Both components of the orogen were believed to have formed a foreland fold-and-thrust belt during Late Cambrian collision with an intra-oceanic island arc: the composite Bowers-Stavely Terrane (Weaver, 1984; Gibson, 1987; Flottmann et al., 1994).

Many of these features contrast with findings from the present study. For example, no granites of any type, pre-, syn- or post-tectonic are found within the Koonenberry FTB; thrusting is thin-skinned, that is there is no crystalline basement involvement, and thrust stacks were emplaced "cold", without attendant high T-low P metamorphism. Because of the lack of magmatism and associated thermally-induced strain softening (cf. Jenkins & Sandiford, 1992), the first phase of deformation in the Koonenberry FTB is relatively structurally simple. However, later Silurian deformation has added a further 215 veneer of structural complexity, including out-of-sequence thrusting and metamorphic overprinting, not seen in the AFB-Wilson Terrane segment of the orogen. In general, the Cambro-Ordovician facies associated with the Koonenberry FTB (including the Ponto Complex) have deeper water and/or oceanic affinities compared to the continental rift-basin facies preserved in the AFB (Preiss, 1987; Jenkins, 1990).

The major similarity between the Adelaide FTB-Wilson Terrane and the Koonenberry FTB is the apparent divergent thrusting (Corona Fault, Koonenberry Fault) bounding the fold belt.

More recent work by Haines & Flottmann (1998a) identified possible foreland-basin style sedimentation for the AFB, which has no analogue within the Koonenberry FTB. Their model implies that a substantial thrust stack load had developed on the continental crust by 522.8 ± 1.8 Ma, the age of a tuff band within the possible foreland- basin package. Coincidentally, this age overlaps that of the first syn-tectonic granite on Kangaroo Is., with a Rb-Sr age 523 ± 6 Ma (Preiss, 1995). This in turn requires an even earlier, pre-Early Cambrian age for the onset of the Delamerian Orogeny.

There are significant difficulties with this foreland-basin model and an Early Cambrian onset of deformation recorded in the internal rather than the external zones of the Delamerian Orogen (the latter including the Koonenberry FTB). The arc-continent collision mechanism proposed by Gibson (1987) for the Ross Orogen in the Wilson Terrane, and by Flottmann et al. (1994) for the Delamerian Orogen, with the "Stawell Terrane" being the implied collider, appears to rule out an Early Cambrian onset of deformation. Recent workers have redefined the Stawell Terrane (Cayley & Taylor, 1998; Cayley & Taylor, in press), and the "Stawell Terrane" of Flottmann et al. (1994) is probably the equivalent of the Glenelg Zone of Moore (1996), which is described more fully in the next chapter. In any case, the age of the proposed collider, from dating of deformed gneissic tonalite in the VIMP 11 drillhole in western Victoria, is 504 ± 8 Ma, which is Late Templetonian (Maher et al., 1997). This date statistically matches the age of the collider inferred in the Tyennan Orogeny in Tasmania: mafic tonalite from the Heazlewood Complex is dated at 510 ± 6 Ma (Early Cambrian)(Tumer et al., 1998). Metamorphism of the Tasmanian sequence occurred at 502 ±8 Ma (Undillan) (Turner et al., 1998). These dates are consistent with the Iverian-Idamaean, and pre-Mindyallan ages of deformation recorded in the Koonenberry, if a diachronous deformation due to irregular collisional geometry is taken into account (see Chapter 8). Given these ages of formation and subsequent deformation for the rocks that are implied to have caused the Delamerian Orogeny, it is difficult to accept an onset of 216 collision-related deformation any earlier than about 516 Ma. Coincidentally, this is the age of the Rathjen Gneiss, which is the most widely accepted indicator of the onset of deformation in the AFB. 217 Chapter 10: Glenelg Zone, western Vic 10.1 Rationale 10.2 Regional geology 10.3 Geophysical studies 10.4 Petrology & whole rock geochemistry: Miga & Dimboola subzones 10.5 Chromite geochemistry 10.6 General Implications: Relationship to Koonenberry Belt 218

Chapter 10: Glenelg Zone, western Victoria

10.1 Location. Reasons for study.

Scheibner (1990) postulated the possible continuity of high-amplitude, long wavelength geophysical anomalies in western Victoria with gravity and magnetic anomalies of the Koonenberry and Scopes Range belts. These features in western Victoria had been earlier identified by Brown et al. (1988), and from east to west, been termed the Padthaway Ridge, Menindee-Renmark Trough and Stavely-Lake Wintlow Belt.

These three features were only speculatively attributed to source rocks, in the absence of basement-penetrative drilling or petrophysical data. The Padthaway Ridge anomaly was attributed to metasediments and higher grade metamorphic rocks (amphibolites, gneisses) and Early Ordovician granitoids of the Adelaide Fold Belt (Brown et al., 1988). Scheibner (1990) correlated these rocks with the now-discredited "Mt Wright Terrane", and interpreted the composite feature as a deformed volcanic arc. This correlation is clearly erroneous, as neither the NSW volcanic rocks (Crawford et al., 1998) or South Australian granites (Foden et al., 1989) have arc affinities, or affinities with each other.

The Stavely-Lake Wintlow Belt, now called the Dimboola Subzone in Victoria (Moore, 1996), was believed to be sourced by basaltic and andesitic volcanics, serpentinites, chert, and volcaniclastic sediments (Brown, et al., 1988). This interpretation has changed little since (cf. Moore, 1996), and has recently been validated by basement intersecting drillholes in the Victorian segment (Maher et al., 1997) and in South Australia (Rankin et al., 1992). Scheibner (1990) also interpreted this feature as a deformed Cambrian arc, possibly on the basis of exposed broadly arc-type volcanics at Mt. Stavely (Buckland, 1987). It has since been shown (Donaghy, 1994; Crawford et al., 1996a) that these are a post-collisional volcanic suite, and not arc volcanics. However, slices of subduction-related forearc boninitic rocks occur elsewhere in the Dimboola Subzone (O'Neill, 1994; Maher et al., 1997).

The Menindee and Renmark Troughs are zones of gravity and magnetic lows separating the Padthaway and Stavely-Lake Wintlow belts. Brown et al. (1988) attributed these lows to concealed ?Late Silurian-Early Carboniferous infrabasins filled with low density, non-magnetic non-marine sedimentary rocks. Scheibner (1990) postulated the existence of an Early Cambrian inter-arc rift basin as an alternative explanation for these features. 219

Petroleum wells drilled in the Renmark Trough area intersected deformed metasediments, which were all assigned to the Cambrian Kanmantoo Group (Thornton, 1974). No arc volcanics or granites were intersected. The basement was unconformably overlain by between 1500 and 600 m of Devonian red bed sandstones and brown shales.

Two wells drilled in the Menindee Trough completed in Late Devonian MuIga Downs Group, while a th:rd, Byrnedale-1, intersected Mootwingee Group and unidentified phyllite and foliated chloritic basaltic andesite between 2200 and 2596 m (NSW Geological Survey, 1993). This volcanic-sedimentary package may be correlated with the Ponto Complex. These lines of evidence argue against an inter-arc rift origin for the Renmark-Menindee Troughs, and suggest that the best interpretation for the low gravity and magnetic features is a series of en echelon Devonian rift basins formed on older, non-magnetic Delamerian-age crust.

In summary, it appears that deformed sequences of the Koonenberry Fold Belt can be traced under the Menindee Trough, and sequences of the Adelaide Fold Belt under the Renmark Trough. The relationship of the economically significant (Crawford et al., 1996a) Lake Wintlow-Stavely belt to these two fold belts and their precursor tectonic settings is the subject of this chapter. ‘

This study draws together recent results from other workers in an attempt to unify the diverse datasets (geophysics, petrology, geochemistry, structural geology, mapping) and provide a coherent model of western Victorian geology with which to compare the Koonenberry fold and thrust belt.

10.2 Regional geology

For the purposes of the following discussion, the nomenclature of Moore (1996, 1997) has been adopted, and in some cases; augmented. Note that these names are applied to interpretive geophysical map units, rather than stratigraphic units, and so are considered informal usages.

10.2.1 Glenelg Zone

This zone is bounded to the east by the major Moyston Fault (Moore, 1996). Cayley & Taylor (1997, 1998) interpreted this structure as the major bounding thrust between Palaeozolc Geology (Met 250 OW Geokocai Mep

111 Glenelg Zone

Sta well Zone

• VIMP VIMP

-- 50. Contoured depth to basement 50m intoneal

Location ot 1:250 000 map sheets shown cc, *Modified from Maher et al., 1997. Figure 10.1.1 Locality Map Glenelg Zone. Figure 10.1.2 Subzones of the Glenelg and Stawell Zones

LEGela &nisi Zatit I. Wcconel Demob 2. Oorn Du a Pep Maar 4. Gmbh Dana, & Patrin Moab 6. Wanacknabind 13=017. Crywebn Omar I. WilonIxta Dow& 9. Oxbi Dom* 10. Tarargut Death 11. Bcinta DozwEi 10. Carko Dan* 12. Carte Mash 14. De Dan Dannb IS. Wypw6d1 Candi 16 Pdaaro DowW1

and; Zrat Dimbaol &tom* 17. Kau Drub 11 Comp Dowel 19. Kartninil Mania 211. Ltle Baty Deinsh 21. Daltin !knob 22 MI6 Moab

Upson &tame a &awe Dcasil Cafro Ocando 2& punts Wolin 25. Gwarnatwy Moth 27. AlAkttle Cuoth 26. Nato Oceratt 02■112dwok Stant 21 19Ibby Dorrail Wabo Dos* 01. Yew Oomah

LEGO*

Stara Iwo 1. Wanacintbal Ocmaln2. Oyowlon Menai, 1 W6onbliu Doraii 4. Orker Donsin S. Corm Dumb 6. Tinewurk Mush 7. O.40 Cowin

Gblat acne. Derbxte &tans Wan Donwit 9. Dello Oat* 16. 16 Al Daraln

Allp &taws 11. Wyn Win Ocaoin 12. Jalurotx Dovail 11 51. Mgr Owodn 14. flornow Daub

Ozeniathoo k Sutcrax IS. YwcyDanek 16. Dux6oppedy Daub 17. Barton Daub ( modified from Moore, 1999 &1997)

V ,DUNT ARAP1LES MIGA SUBZONE

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Cambrian - Ordovician (St Arnaud Grou

Figure 10.1.3 Locality Map and Regional Geology, Grampians- Black Range-Mt Stavely Area (modified from Buckland & Ramsay, 1982; & Cayley & Taylor, 1997)

Key: A = Mt Drummond; B = Lake Lonsdale; C = Mt Dryden; ; D = Mokepilly; E = Bellellen; F = Jallukar; G = Barton; H = Mt Elliot; I = Mt Stavely; J = Tyar belt; K = Black Range belt; L = Glenisla belt. Figure 10.2.1 Locations of VIMP drillholes over TMI, western Victoria

INusiern Ihcford. I rogrictic ,,let ,:nage twin. magema low) writ: an east-west gradent Altered intensrty ayer he data used to couple tie image carres horn the G.S.V AC-SO arc CRAE Surveys

VIMP-6 VIMP-14

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Location Di 1:250 000 map sheets shown 142 33'

"modified after Maher et al. (1997) 220 the Lachlan Fold Belt in the hangingwall, and the eastern extension of the Adelaide Fold Belt in the footwall. Thus the Glenelg Zone can be considered to be entirely part of the Delamerian Orogen. Metaturtiditic and metavolcanic rocks of the Stawell Zone to the east of the Moyston Fault were emplaced during the Silurian, and merit no further discussion here.

Moore (1996) divided the Glenelg Zone into four subzones: from west to east, the Ozenkadnook, Miga, Upson and Dimboola Subzones (SZ).

10.2.2 Ozenkadnook SZ

The Ozenkadnook SZ was interpreted by Moore (1996) to comprise domains of higher grade metasediments. These were correlated in part with the Glenelg Metamorphic Complex, which crops out as clastic, carbonate, shale and volcanic sequences metamorphosed up to andalusite facies (Gibson & Nihill, 1992). Parts of the domain were also inferred to comprise low grade Kanmantoo Group sediments (Moore, 1997) or metavolcanic ("greenstone") belts (Moore, 1996). Moore (1997) postulated structural equivalence between the Ozenkadnook SZ and the Rocky Cape Block of northwestern Tasmania.

Drilling of magnetic anomalies in the Yanipy domain of the Ozenkadnook SZ has revealed a complex tectonic environment. Jackson (1996a) reported amphibolite after cumulate gabbronorite in DUMB-1, drilled on a circular magnetic feature. This rock, and cumulate metagabbro subsequently drilled in VIMP-2 (Maher et al., 1997; Figure 10.2.1) also in the Yanipy domain, have been correlated with the Black Hill Norite in South Australia. However, a SHRIMP U-Pb zircon age from the VIMP-2 gabbro returned an Early Cambrian age of 524 ± 9 Ma, which is statistically unlike the 487 ± 5 Ma (Early Ordovician) Rb-Sr whole rock age from the Black Hill Norite reported by Schmidt et al. (1993). Rajagopalan et al. (1993) summarises evidence for a post- Delamerian age for the Black Hills Norite, including lack of deformation and metamorphism, undisturbed K-Ar ages from biotites of 486 Ma, and a Nd-Sm whole rock age of 489 ± 10 Ma. In the light of this evidence, there are three possible implications for the correlation made by Maher et al. (1997). The first is that the SHRIMP age from the VIMP-2 gabbro is an inherited zircon age, and the correlation with the Black Hills Norite is valid; the second is that both ages are correct, and the two suites are unrelated; a third, if unlikely, possibility is that the mafic magmatism represented by these rocks spanned a period of some 37 Ma, and migrated from east to west. The first possibility is ruled out by the discussion of Fanning in Maher et al. y 221 (1997), which indicates that the zircons from VIMP-2 are definitely magmatic, and show no excess scatter, which would be expected if inherited components were present. Thus it appears that the second possibility is most likely, namely that the two suites are unrelated. Perhaps significantly, the age of the VIMP-2 gabbro is statistically indistinguishable from the 525 ± 8 Ma from the Cymbric Vale Formation in the Koonenberry Belt (Zhou & Whitford, 1994; Chapter 4) and the 526 ± 4 Ma age from the Heatherdale Shale in the Adelaide Fold Belt (Cooper et al., 1992; Chapter 8). A significant and widespread 525 ± 5 Ma magmatic event is indicated.

Two drillholes at Yanac South (Figure 10.2.1) targeting an arcuate magnetic feature were reported by Jackson (1996b). These yielded serpentinised olivine-rich cumulates and picrite lavas (Maher et al., 1997). This unusual suite is not amenable to dating, but geochemistry (Maher et al., 1997) suggests that the Yanac South rocks have greatest affinity with Neoproterozoic basalts found on King Island (Waldron et al., 1993); this hypothesis is investigated below.

A further two drillholes, VIMP-7 and VIMP-13 were drilled on the arcuate feature targeted by the Yanac South drillholes (Maher et al., 1997). Both intersected gt-plag- clz-qz-mu-bio schist. K-Ar dating of muscovite and biotite from VIMP-13 indicate a metamorphic age of 501 ±4 Ma (ibid.), that is, syn-tectonic to the Delamerian Orogeny.

Drillhole VIMP-12 was Iodated over a magnetic anomaly interpreted as a polydeformed fold-nose (Maher et al., 1997). This hole intersected migmatitic gneiss. A variety of ages was obtained by Maher et al (1997) for components within this rock. Rounded zircon cores, representing an original sedimentary protolith or recycled crustal material, as well as a minor igneous population, give ages around 1030 Ma. However the bulk of the zircons in the rock are magmatic zircons with a 589 ± 14 Ma age; this age is also recorded by overgrowths on older grains. Micas from both the restite and neosome phases gave K-Ar ages of 490 ± 4 Ma and 497 ± 4 Ma respectively. Monazite dated using the U-Pb SHRIMP method gave a 480 Ma age, which is quoted as the lower age limit of gneiss formation. My preferred interpretation of this unit is a felsic igneous rock formed at 589 Ma by mafic underplating of older c.1030 Ma cratonic crust, thus incorporating an inherited zircon component. This rock was then deformed and partially melted during the Delamerian Orogeny (508-487 Ma) to produce the metamorphic ages. 222 In summary, the Ozenkadnook SZ is a complex tectonic region. It contains evidence of continental breakup of older (1030 Ma) crust at about 589 Ma, and a second lithospheric thinning event (Turner & Foden, 1990) at around 525 Ma. The subzone also incorporates deformed Delamerian elements from the period c. 510-487 Ma. These features have significant affinities with the Koonenberry FTB.

10.2.3 Miga SZ

The Miga SZ was interpreted by Moore (1996) as a zone of biotite to sillimanite grade metasediments correlated with the Glenelg Metamorphic Complex. In addition, this SZ contains magnetic metavolcanic rocks which are believed to be the extension of the Black Range Volcanic belt, which crops out to the south (refer Figure 10.1.3). The SZ is bounded to the west by the Yarramyljup Fault, and to the east by the Escondida Fault (Figure 10.2.1). Geometric patterns of magnetics within the Miga SZ suggest that parts of it have been thrust westward across the Ozenkadnook SZ (Moore, 1996). The Yarramyljup Fault is stitched by the post-tectonic Harrow Granite (Cayley & Taylor, 1997), which has a 466 ± 6 Ma K-Ar age (Richards & Singleton, 1981). This Early Ordovician date is the minimum age at which these two subzones could have been juxtaposed. The Escondida Fault is also stitched by a post-tectonic intrusive, the Bushy Creek Granodiorite (Cayley & Taylor, 1997); a Late Cambrian SHRIMP U-Pb zircon age of 495 ± 5 Ma has been reported for this pluton (Stuart-Smith, 1994, cited in Cayley & Taylor, 1997).

The Black Range Volcanics mostly crop out in a 25 km long, northwest-trending belt approximately 35 km west of Halls Gap (Figure 10.2.1). A smaller (<10 km strike length) belt, the Glenisla Belt, crops out to the east of the main belt. A third belt to the west of the Black Range, the Tyar or Rocklands (Brookes, 1997) Belt, has been inferred from aeromagnetics and limited drilling. Cayley & Taylor (1997) distinguished four unnamed lithological associations within the Black Range Volcanics: ultramafic to intermediate volcanics, occurring in all three belts; intermediate to felsic volcanics, on the eastern side of the main belt; black slate, in the Black Range and Glenisla Belts; and quartz-rich metaturbidites, also in both outcropping belts.

Igneous rocks from all three belts show deformation fabrics, and contain the metamorphic assemblage ab-ser-chl-act, indicating a lower greenschist metamorphic facies. The metasedimentary rocks have unclear stratigraphic relationships to the igneous units, but show structural and metamorphic conformity, with well-developed cleavage and schistose fabrics (after Cayley & Taylor, 1997). 223

Samples from drillholes in the Black Range Volcanics at McRaes Prospect (centred around 600000 mE 5884200 mN AMG Zone 54) have been petrographically examined and geochemically analysed to determine the tectonic affinity of these rocks. Results from this study are outlined below (10.5)

In 1997, three basement intersecting diamond drillholes were completed within the Miga SZ, to the north of the Black Range (Maher et al., 1997). VIMP-1 (Figure 10.2.1) intersected a post-tectonic mafic tonalite, which was interpreted as a mafic phase of the Duchembegarra Granite (Moore, 1996). This intrusive stitches the three domains of the Miga SZ across a northwest-trending structure. SHRIMP U-Pb dating on magmatic zircons (Maher et al, 1997) gave an age of 404 ± 6 Ma (Early Devonian) for this pluton, limiting the assembly of the Miga SZ to before this time.

VIMP-3 completed in a hydrothermally altered andesitic lava and lava breccia package. These rocks were metamorphosed up to prehnite-pumpellyite grade. Geochemical analysis of two plagioclase + augite-phyric andesites (Crawford in Maher et al., 1997) showed that these rocks have medium-K calc-alkaline affinities, with characteristically low TiO2 values indicating a possible correlation with the ?Late Cambrian Mt Dryden Belt of the Dimboola SZ (see below).

VIMP-11, targeted over a northwest-trending magnetic high, drilled a mafic diorite to tonalite with a zonal gneissic foliation. SHRIMP U-Pb dating on magmatic zircons returned a date of 504 ± 8 Ma (Middle Cambrian). The gneissic foliation obviously post- dates this, but may still be Delamerian in age, making this unit syn-tectonic. Crawford (in Maher et al., 1997) precluded correlation of this unit with either the contemporaneous D2 tholeiitic dyke suite (510 ± 2 Ma; Chen & Liu, 1996) or the younger A-type granite suite (e.g. Mannum Granite 481 ±9 Ma; Preiss, 1995) of the Adelaide Fold Belt.

In summary, the Miga SZ comprises metavolcanic and metasedimentary slices with a strong north to northwest tectonic trend. The age of at least some of these slices is Middle and Late Cambrian, with deformation and metamorphism having been completed towards the end of the Delamerian Orogeny at c. 495 Ma. By inference, this date is also latest time that the three subzones of the Glenelg Zone could have been initially assembled. 224 10.2.4 Upson SZ

The Upson SZ only occurs on the Ouyen 1: 250 000 map sheet (Moore, 1997), but extends into South Australia. It is bound to the east by the Skriety Fault, which is interpreted as being a steeply west-dipping fault, possibly a thrust (Moore, ibid.). Other internal boundaries within the SZ are sympathetic to the form of the Skriety Fault, which led Moore (1997) to postulate that the Upson SZ was a Delamerian west-dipping thrust stack. The interpreted source lithologies of the Upson SZ are all inferred to be metasedimentary, with the exception of the magnetic Gunamalary domain, interpreted as serpentinite or mafic volcanics. The continuation of the Upson SZ on the South Australian side of the border was drilled by the Peebinga-1 drillhole (Rankin et al., 1991), which intersected metabasalts interbedded with limestone, marble and shale. As shown in the previous chapter, the basalts from Peebinga -1 have affinities with the Truro Volcanics and the MAV, and may be part of a c. 590 Ma rift package.

10.2.5 Dimboola SZ

The Dimboola SZ is a major high-amplitude, long-wavelength magnetic feature of continent-scale significance. It is the most prominent anomaly in Victoria, with dimensions of c.45 km width, c.240 km length and 450 nT amplitude above the regional background. Moore (1996) interpreted this feature as being sourced mostly by basaltic metavolcanic rocks. Because of differences in magnetic wavelength within the subzone, Moore (1996) further divided it into three domains. These are discussed separately.

The Ni Ni Domain is characterised by a region of high-amplitude (up to 500 nT), high frequency lineaments. These were believed by Moore (1996) to be sourced by serpentinised boninitic slices and slices of calc-alkaline rocks of the Mount Stavely Volcanic Complex (MSVC). VIMP-8 (Maher et al., 1997) was drilled on the Ni Ni domain, and intersected a strongly hydrothermally altered andesite-dacite lava and interbedded volcaniclastic sediment package. Data presented by Crawford (in Maher et al., 1997) suggest a correlation between these rocks and the Mt Dryden Belt (see 10.4 below). Notably, the rocks intersected are not significantly magnetic (maximum k = 120 x 10-5 SI; average 45 x 10-5 SI; data after Maher et al., 1997).

North Ltd drilled five basement intersecting drillholes within the Ni Ni domain (data from O'Neill, 1995). DIMB-RM2 intersected hydrothermally altered lapilli tuff and hyaloclastite. DIMB-RM5 and DIMB-RM7 both intersected metamorphosed gabbroic 225 rocks with the metamorphic assemblage ab-epi-act-chl-serp ± zoi, indicating upper greenschist facies conditions. Crawford (in Horvath & O'Neill, 1994) interpreted rocks from -RM5 as pyroxenite-wehrlite, and from -RM7 as microgabbro. These interpretations suggest that at least part of the Ni Ni domain is similar to mafic- ultramafic complexes (MUMC) observed in Tasmania (Berry & Crawford, 1988). ARKO-RM1 and -RM2 (O'Neill, 1994) also intersected metabasalt + metagabbro, and metagabbro respectively. These rocks contained the assemblage serp-act-chl-zoi-qz- carb, also indicating upper greenschist metamorphism. Crawford (in Horvath & O'Neill, 1994) suggested that these rocks were high-Mg, low-Ti rocks derived from boninitic magmas, thus strengthening the correlation with the Tasmanian MUMC.

The Dahlen Domain makes up the bulk of the high-amplitude, low-frequency response of the Dimboola SZ. Moore (1996) believed it to be sourced at depth by mafic volcanics of the Mt Stavely Volcanic Complex (MSVC) overlain by a non-magnetic cover of Silurian Grampians Group. It is questionable whether an unit within the MSVC is magnetically susceptible enough to generate such a large anomaly without extreme volumes. Two drillholes by North Ltd fall just inside the western boundary of the Dahlen domain (data from O'Neill, 1995). DIMB-RM3 intersected serpentinised gabbro and metapyroxenite, interpreted by Crawford (in Horvath & O'Neill, 1994) as a high-Ca boninitic rock; DIMB-RM8 completed in serpentinite of unknown affinity. The similarity between these two samples and the units drilled in the Ni Ni domain, and the fact that both holes were sited on an arcuate magnetic high on the boundary between the Ni Ni and Dahlen domains may either suggest a problem with the chosen domain boundary, or alternatively, solve the susceptibility problem alluded to above. Section 10.3 addresses this question in more detail.

The Kalkee Domain is bounded by the Moyston Fault, and overthrust by amphibolite grade rocks of the Stawell Zone (Cayley & Taylor, 1997). It is a zone of high gravity and high-amplitude, high-frequency magnetic responses (100-500 nT). The source for these anomalies was interpreted to be a northwestern extension of the exposed Mt Dryden Volcanic Belt (see below). Four basement intersecting drillholes are reported by Maher et al. (1997). VIMP-9 drilled weakly deformed tholeiitic basalt, peperite and red shale. Crawford (in Maher et al., 1997) postulated a correlation between these rocks and tholeiites from the Magdala mine sequence in the Stawell Zone. However the two packages have different metamorphic grades and structural complexities (Maher et al., 1997). 226

VIMP-6 bottomed in a serpentinite-harzburgite complex. Crawford (in Maher et al., 1997) proposed equivalence between this unit and the Tasmanian Mafic-Ultramafic Complexes (Berry & Crawford, 1988). This correlation has been investigated using the geochemical signature of relict chrome spinel phenocrysts (see 10.5).

Drillhole VIMP-16 terminated in deformed but uncleaved siltstone and greywacke of the Glenthompson Sandstone. These rocks have been metamorphosed to chlorite grade. The Glenthompson Sandstone is a Late Cambrian unit that is inferred to unconformably overlie the MSVC (Cayley & Taylor, 1997). It is interpreted as a syntectonic foreland basin deposit (after Maher et al., 1997).

The Mt Dryden Volcanic Belt occurs as a northwest-striking, discontinuous series of outcrops between Mount Drummond and Mount Elliot, approximately 55 km to the southeast. The principal sites where Mt Dryden Volcanics crop out are (from north to south) Mt Dryden, Mokepilly Rd, Bellellen, Jallukar, Barton and Mt Elliot (Figure 10.2.1). The Mt Dryden belt was mapped by Buckland (1987), who described a variety of lithologies including hydrothermally altered basaltic andesite to rhyolite lavas, thick volcaniclastic breccias, laminated volcaniclastic sandstones and siltstones. Intrusive phases range from basalt dykes through to diorite plugs. Preserved volcanic fades include pillow lavas and mass flow breccias, indicating a submarine origin. The extensive breccia units have been tentatively correlated with the Fairview Andesitic Breccia of the MSVC (Buckland, 1987).

The Frying Pan prospect lies to the east of the main Mt Dryden Belt, near the town of Moyston and just to the west of the Moyston Fault. This places the Frying Pan prospect within the Kalkee Domain. Drillholes by CRAE at the Frying Pan prospect intersected altered basaltic and andesitic lavas as well as slices of serpentinised, ultramafic boninitic lavas (Crawford in Menpes, 1994). A suite of these rocks has been geochemically analysed, and the results are outlined at section 10.5.

10.3 Geophysical Model Testing

The main focus of this section is the source or sources of the high-amplitude magnetic anomalies within the Dimboola SZ. In particular, two sections at different locations have been constructed to test two competing ideas: is the Dimboola SZ sourced entirely by rocks associated with a Late Cambrian forearc collisional event, as implied by Moore & Maher (1998)? Or is the Dimboola SZ also partly sourced by a pile of Late Neoproterozoic rift basalts, as postulated by Direen & Crawford (1998a)? 227

10.3.1 Data & Methods

High-quality, publicly available aeromagnetic data owned by the Geological Survey of Victoria are available for the Horsham sheet, with 1994 vintage 400 m and 200 m lines at an 80 m drape specification (Willocks, 1995). These are complemented by extensive 1980 vintage company data with a 250 m line spacing at an 80 m drape. Aeromagnetic data at 400m /80 m specifications also exist for the Ouyen sheet (ibid.). Magnetic data available for this study are shown in Figure 10.3.1.

Gravity data have been improved from an 11 x 11 km grid to a 1.5 x 1.5 km grid by the Geological Survey of Victoria (GSV) during the course of this study. This data has been augmented by selected line acquisition by GSV at station spacings of 250 m. Data available for the purposes of this study is shown in Figure 10.3.2.

Data for both gravity and magnetic modelling were extracted from grids using the processes outlined at section 3.9. Gravity data were then degraded by subsampling to interstation spacings equivalent to the data distribution in each line.

10.3.2 Petrophysical Properties

Bulk wet densities were determined on 59 drillcore samples from the VIMP drilling program. Measurements were made at the GSV Core Library at Werribee, Victoria, in April 1998. A minimum of 250 g of core was used, with immersion in water for a minimum period of 24 hours. After touch-drying, the saturated mass of the samples was measured using an electronic balance with a precision of 0.01 g. The immersed mass of the samples was then measured using the same balance with a cradle attached to an under-hook. Results are summarised in Table 10.3.1 below. Fourteen measurements, using sampling techniques and procedures outlined in chapter 3, were also made on samples taken from outcrops in the Mt Dryden belt. The value for these rocks is probably a minimum due to weathering.

Figure 10.3.1 TMI image for parts of western Victoria, including the Dimboola Subzone. Modelled sections shown.

E141° E141°30" E142° El 42 - 30' ....."I 411

250

-72

-233

-395

50 0 50 100 nT

Kilometers

TMI pseudocolour and intensity layer shaded at 45 degrees from the northeast. Corrected to IGRF 1990 epoch 1995; I = 60 300 nT; Inclination -67.97 degrees; Declination 8.64 degrees. Data courtesy GSV & PIRSA. Key: P =Peebinga-1; Y = Yanac South; Vx = VIMP-x; D = Dimboola prospect; A = Arkona prospect. Figure 10.3.2 Bouguer anomaly image for western Victoria, including the Dimboola Subzone. Modelled sections shown.

E141° E141°30" E142° E14 *30" 325

189

-81

-217

-352

50 0 50 100 um/sec2

Kilometers Bouguer anomaly pseudocolour and intensity layer shaded at 45 degrees from the northeast. Data courtesy GSV.

Key: P =Peebinga-1; Y = Yanac South; Vx = VIMP-x; D = Dimboola prospect; A = Arkona prospect. 228

Table 10.3.1 Measured densities of selected Palaeozoic rocks, western Victoria

Location Lithology p (t/m3) Ozenkadnook SZ VIMP-2 Gabbro 2.95 ± 0.01 VIMP-7 & -13 Biotite schist 2.71 ± 0.02 VIMP-11 Tonalite 2.82 ± 0.02

Miga SZ VIMP-3 Andesite 2.79 ± 0.03 Altered andesite 2.62-2.70

• Dimboola SZ VIMP-8 Andesite-dacite 2.77 ± 0.05 VIMP-9 Basalt breccia 2.93 ± 0.01 Shale 2.77 ± 0.02 VIMP-10 Grampians Gp sandstone 2.42 ± 0.01 VIMP-15 Grampians Gp sandstone 2.42 ± 0.01 VIMP-17 Grampians Gp sandstone 2.61 ± 0.01 VIMP-16 Glenthompson sandstone 2.72 ± 0.01 Mt Dryden Belt rhyolites to andesites 2.75 ± 0.08

Sta well Zone VIMP-4 Basalt 2.88 ± 0.01 Porphyry 2.64 ± 0.01 VIMP-5 St Arnaud Gp pelite 2.70 ± 0.01

Magnetic susceptibility for these rocks was measured by Maher et al. (1997) using a handheld GMS-2 susceptibility meter on the core at 1 m intervals. Results from their work are summarised in Table 10.3.2 below. Also included are susceptibilities from the Yanac South and Frying Pan drillcores, and outcrops in the Mt Dryden belt, measured with an Exploranium KT-6 handheld meter. 229

Table 10.3.2 Measured susceptibilities of some Palaeozoic rocks, western

Victoria

Location Lithology k av (x i0 5 SI) k max (x 10-5 SI) Ozenkadnook SZ YANS-1 Olivine-rich 1620 2560 cumulates YANS-2 Picrite lavas 23 17 VIMP-2 Metagabbro 498 600 VIMP-7 & -13 Biotite schist 0 0 VIMP-12 Migmatite 0 0

Miga SZ V1MP-3 Andesite lavas 3 27 VIMP-11 Tonalitic gneiss 20 145 VIMP-15 Grampians Gp 0 0 sandstone

Dimboola SZ VIMP-6 Serpentinised 198 271 harzburgite VIMP-8 Andesites 120 45 VIMP-9 Basalt 147 550 Frying Pan Basaltic andesites 15 30 VIMP-10 Grampians Gp 0 0 sandstone VIMP-16 Glenthompson 0 0 sandstone Mt Dryden Belt rhyolites to basaltic 100 3000 andesites

Stawell Zone VIMP-5 St Arnaud Gp pelite <1 2 VIMP-14 St Amaud Gp pelite 0 0 VIMP-17 Grampians Gp 0 0 sandstone VIMP -18 Grampians Gp 0 0 sandstone 230

10.3.3 Modelling

Two sections have been modelled, based on proximity to drillhole locations over the Dimboola SZ. These are shown in Figures 10.3.3 & 10.3.4.

The parameters used for modelling the magnetic field are as follows: Magnetic Field Intensity 60300 nT Inclination -67.97° Decllnation 8.64° Height 80 m

Figure 10.3.3 shows the southern modelled section, projected to a depth of 10 km. The gravity field is relatively simple, involving a 20 km wide trough of -30 mGal between two "shoulders" of c.+50 mGal, each of about 5 km width. The magnetic field is also relatively simple, consisting of a 25 km half-wavelength, 600 nT amplitude peak asymmetric to the west, almost coincident with the gravity low. Superimposed on each "limb" are two minor 100 nT peaks of < 1 km half-wavelength. The western high- frequency peak is associated with the Ni Ni domain, the main peak with the Dahlen domain, and the eastern peak, the Kalkee domain of Moore (1996).

The style of solution proposed for this section is an imbricate fan above a duplex, possibly involving crystalline basement. The upper fan is eroded to form a 4000 m deep trough filled with Siluro-Devonian Grampians Group (2.42 t/m3) and minor Murray Basin deposits (2.00 t/m3). These give rise to the large gravity low. Unmodelled topography at the base of the Murray Basin sequence accounts for higher frequency gravity effects in the western half of the low.

The eastern gravity high is modelled by east-dipping, high density (3.10 t/m 3), non- magnetic slices interpreted as amphibolites. The density of the unmetamorphosed Glenthompson Sandstone (2.72 t/m3) is insufficient to explain the gravity high as interpreted by Moore (1996) at this location. The amphibolite slices are bounded to the west by a major fault that also controls the Siluro-Devonian trough. This fault is interpreted as the Moyston Fault, in a position 8 km west of that interpreted by Moore (1996). The high density slices are overthrust from the east by a package of moderate density (2.70 t/m3), non-magnetic rocks interpreted as the ?Cambrian St Arnaud Group. This accords with Moore's (1996) interpretation of the Cannum domain (Figure 10.1.2). Note that the gravity high is unable to be fully modelled even with extreme densities for supracrustal rocks. This is due to a non-two dimensional effect where the Figure 10.3.3 2D gravity and magnetic model, Dimboola SZ, Southern Line

500 00bs. Gray. • Obs. Mag. 450 ,_400 rrns error: 13 rms error: 3.1 ... 350 Gshift: 0 Mshirt: -125 _300 250 200 150 100 _50 0 5 -100 -150

-250

-350 400 -450 -40 -500

lib 6000

10000 35000

V.E. = 4. Key: Tv = Tertiary volcanics; Ty = Murray Basin sediments; SDRS? = possible Seaward Dipping Reflector Sequence basaltic pile.

Figure 10.3.4 20 gravity and magnetic model, Dimboola SZ, Northern Line 10 /500 00bs. Gray. • Obs. Mag. _700 rms error: .22 rims error: O. _600 Gshift: 0 Mshift: -125 _500 400

: l) is 300 Ga ir l

_200 Il (m

_100 3w ity S v

—0 U) J, Gra - 100 -200 .1 5 _-300 _ -400 -500 0

1000 1000 'Up c

— 2000 _2000

31050

emanent

ureole Bulk Crust

5000 1 1 -5000 0 5000 10000 15020 20000 25000 30000 Distance (m) V. E. =6. Key: MUMC = Mafic-Ultramafic Complex; Msed = metasediments; Dryden = Mt Dryden Belt volcanics / volcanoclastics; SDRS? as above. 231 line of section intersects the termination of the gravity anomaly. The relatively low- amplitude magnetic anomaly coincident with the gravity high is modelled with a thin slice of dense (2.97 t/m3), weakly magnetic (25 x 10 -5 SI) tholeiitic basalt. Tholeiitic basalt was intersected in VIMP-9, 2 km north of the section (Maher et al., 1997). However, the low greenschist grade and higher magnetic susceptibility (ay. 150 x 10 -5 SI) of the VIMP-9 rocks is inconsistent with the high gravity-high metamorphic grade, low magnetic signature observed. The VIMP-9 hole may have drilled a detached horse from the footwall within this major fault zone (cf. Cayley & Taylor, 1998).

The western gravity high is modelled by two dense packages of rocks, one strongly magnetic, the other only moderately so (2.80 t/m 3 / 12000 x 10-5 SI "SDRS?"; 2.97 t/m3/ 120 x 10-5 SI "Ni Ni"). The slab-like body labelled SDRS? is responsible for the major magnetic high, whereas the packages labelled "Ni Ni" give rise to the gravity high. Note that these sources occur above and below the major magnetic body, and may well have different origins. The lower of the two bodies may be a gabbroic complex related to the main magnetic source; the latter is interpreted as a major basaltic pile with significant serpentinisation to produce the elevated susceptibilities. The upper Ni Ni source is interpreted as a slice of boninitic ophiolite, in accord with drillhole evidence outlined above (10.2.4). The small magnetic anomaly superimposed on the western side of the high is sourced by a small plug of Tertiary basalt, identified by Moore (1996) to the southwest of Horsham.

Underlying the upper thrust stack is a section interpreted as a duplex. At the western end of the section, this involves the high density (2.82 t/m3) moderately magnetic (120 x 10-5 S1) Wyn Wyn domain of the Miga SZ. These properties are extrapolated from Late Cambrian tonal itic gneiss drilled in VIMP-11. Stacked above and below the Wyn Wyn are bodies with the properties of bulk continental crust (2.67 t/m 3; 0 SI). To the west of the section, the lower of these bodies subcrops as the Ozenkadnook SZ, which is interpreted as a metasedimentary complex (Moore, 1996). Drillholes in the Ozenkadnook are not broadly representative of metasedimentary lithologies, so properties from them have not been used in modelling. In any case, this source is generally too deep and too far west to have much impact on the calculated field.

Figure 10.3.4 shows the more complex northern section, projected to a depth of 5 km. The gravity field is broadly similar to that of the southern section, with a broad low of some 15 km half-wavelength and -15 mGal amplitude. Narrow shoulder highs are not present. The magnetic field is considerably more complex than that to the southeast, consisting of mirror symmetric pairs of spike anomalies (600/400; 800/200 nT, 5 km 232 ?J2). These are centred around a broad, 15 km X/2, 600 nT high with asymmetry to the west. A medium frequency -500 nT low is developed at the western end of the section. The three magnetic highs correspond to the Ni Ni, Dahlen and Kalkee domains.

A similar style of solution to that of the upper imbricate fan of the southern section is proposed. Areas left unshaded are attributed the properties of bulk continental crust. Again, the thrust stack has been eroded to form a trough containing the Grampians Group (2.47 t/m3), providing the main gravity low. A 200 m veneer of low density (2.00 t/m3) Murray Basin sediments overlies this, reflecting the deepening of this basin to the north relative to the southern section (Moore, 1996).

The deep magnetic low to the west has been modelled using a negative remanently magnetised (1200 x 10-5 SI; 70° inclination, 10° declination) aureole to a pluton of the Duchembegarra Granite drilled in VIM P-1. The aureole surrounds moderately magnetic granite with no remanance (2.67 t/m 3; 120 x 10-5 SI). This Devonian granite (404 Ma: Maher et al., 1997) stitches the three subdomains of the Miga SZ (Moore, 1996); its apparent non-involvement in the thrusting west of the Moyston Fault is consistent with this interpretation.

The two pairs of magnetic spikes are explained by essentially similar geology. From west to east the western pair is modelled by: serpentinised boninite 2.67 t/m3 4800 x 10-5 SI metasediment 2.63 0 andesitic volcanics 2.72 2400 greenschist metasediments 2.73 0

From west to east, the eastern pair is modelled by: andesitic volcanics 2.72 t/m3 1800 x 10-5 SI metasediments (cherts?) 2.63 0 serpentinised boninite 2.67 6000

Structurally above the eastern serpentinite body are the greenschist grade (2.71 - 2.67 t/m3) metasedimentary rocks of the St Arnaud Group (Crymelon domain: Moore, 1996). It is unclear in this model whether the Moyston Fault passes to the west or east of the eastern serpentinite body, or through it. VIMP-6, 6 km southeast of the line, intersected serpentinised and highly sheared metaharzburgite. Maher et al. (1996) also noted this ambiguity, and suggested analysis of chromites would provide a solution to this problem. Such an analysis is outlined below (section 10.5). 233

The main low-frequency magnetic anomaly in the centre of the section has composite sources. A higher frequency anomaly on the western side of the broad high is modelled by a slice of metabasalt (2.80 t/m3, 4800 x 10-5 SI). Below this is a larger volume with the same properties, which sources the main low frequency anomaly. The upper slice may therefore be sliced off the lower one sometime after the emplacement of the western thrust stack, but before deposition of the Grampians Group. The main anomaly source in this northern section is comparable in density to that in the southern source, but c. 50% less magnetic.

10.3.4 Discussion

The following features are derived from both models, and allow general inferences about the Dimboola SZ to be made. Important features include: • west-vergent thrust geometry; • thrust involvement of an older Late Neoproterozoic volcano-sedimentary pile (Ozenkadnook SZ) (589 Ma magmatic age, crustal and lithospheric mantle melts: VIMP-12, Yanac), and possibly older cratonic crust; • thrust involvement of an Early Cambrian volcano-sedimentary pile (Miga SZ) (524 Ma magmatic age, crustal melts VIMP-11); • thrust involvement of undated, pre-Ordovician mafic-ultramafic slices, many with boninitic affinities: affinities to Tasmanian MUMC may imply an Early Cambrian age for these rocks (the Heazlewood Complex in western Tasmania is dated at 510 ± 6 Ma; Turner et al., 1998); • volcanic slices fault-interleaved with boninites are probably related to the Mt Dryden Volcanics.

A major Delamerian deformation event with attendant metamorphism, dated at c. 500 Ma affected the Ozenkadnook and Miga SZ's, with craton-vergent thrusting. However final thrust deformation may not have occurred until the Silurian, due to the imbrication of volcanics that are post-collisional with respect to the Delamerian Orogeny. Stitching and cratonisation of the Miga SZ occurred in the Early Devonian, with the intrusion of the Duchembegarra Granite.

The presence of significant volumes of mafic volcanics, as east-dipping thrust slices beneath the Dahlen subzone is confirmed by these models. The densities of these bodies are consistently in the basalt range (2.80 t/m3), with the southern slice being more magnetic. The wedge shapes of these bodies tend to suggest original prismatic 234 basaltic piles, which lends some support to an origin as Seaward Dipping Reflector Sequences (SDRS) (Direen & Crawford, 1998a). However the association with boninitic slices to both east and west may also supports a forearc origin (Moore & Maher, 1998). Therefore, in the absence of other data, the geophysical data remain ambiguous on the question of whether the Dahlen domain represents a break-up or collider association (see below).

10.4 Petrology & Whole Rock Geochemistry: Yanac South; Frying Pan; McRaes and Mt Dryden

Crawford & Direen (1998) suggested a tectonic classification of Late Neoproterozoic- Palaeozoic igneous rock suites in southeastern Australia. These include break-up, collider and post-collisional associations, which are best documented in Tasmania (Crawford & Berry, 1992). Sampling and geochemical evaluation of igneous suites in western Victoria drilled during recent minerals exploration activity in the Yanac South, Frying Pan, and McRaes prospects, suggests that all three associations are present in the Glenelg Subzone. The evidence for this is outlined below.

10.4.1 Break-up suite: Yanac South

Core from drillholes YANS1 and YANS2 was supplied by MIM Exploration. The intervals in YANS1 were 256.0, 279.0 and 298.8 m; in YANS2, the intervals supplied were 216.6, 224.4 & 243.2 m. Thin sections reveal that these are highly altered rocks, with altered ol phenocrysts and interstitial cpx in a matrix of serp-talc-chl plus secondary magnetite. Large (up to 2 mm) lantern-shaped ol phenocrysts in YANS2 are generally pseudomorphed by a mixture of serp-chl. The olivine-rich nature of samples from YANS1 suggest that these rocks are cumulates, whereas YANS2 samples are more like altered picritic lavas. The cumulates may well be ol-enriched basal portions of the very fluid picritic lava flows.

All six samples were analysed for major and trace elements using standard wholerock techniques. Volatile free data are reported in Maher et al.(1997). LOI's ranged from 6.2 to 12.08 %, due to hydrated alteration phases such as talc and serpentine. Major and trace element diagrams are presented in Figure 10.4.1. The field for picrites from King Island is taken from Waldron et al. (1993).

Immediately obvious in the major element diagrams is the presence of three groups from the Yanac South drillholes. Analyses with MgO 35-40% are two cumulates from 50 — 16 - King Is 48 — 14 — Cumulates 12 — 46 — ii. 10 — cv 244— a. 8 — i 42 — 6— • 4 — 40- 4 2— • • • 38 I I I I 0 20 25 30 35 40 20 25 30 35 40

0.5— 12 — - 10 — 0.4 — 8— 0.3 — OA o 0.CL 6 — i= >- 0.2— 4 — •• 0.1— 2 — • • • • 0 0.0 I I I I 20 25 30 35 40 20 25 30 35 40

12— 40 — •• 35 — 10 — 30 — 8 — el 8. 0 20— • 74 0 • • w 15 — 4— • • 10 — 2 — 5 — 0 • l I I I 0 20 25 30 35 40 20 25 30 35 40 Mg 0 (Wt%)

12 — 2000 10 — • • 1800 1600 8 — 1400 I 1200 11 .c,-3; 6 — 11 u. & 1000 P 800 4_ • 4 points 600 i Ti/Zr =100 2 — 400 200 0 I I I I 0 20 25 30 35 40 0 5 10 15 MgO Zr (ppm) Figure 10.4.1 Oxide/element variation diagrams, Yanac South Field for King Is from Waldron et al. (1993) 235 VANS 1, whereas samples with MgO 20-25% are picrite lavas; the latter tend to cluster with the King Is. samples. The key feature of use in determining the magmatic affinities of the Yanac picritic lavas is their low TIO2 content compared with MORB or 01B-type picrites (cf. O'Nions & Clarke, 1972)

The Yanac South picritic lavas (and olivine accumulate complements) are compositionally and petrographically very close to the Late Neoproterozoic picrites on King Island. Both suites of these unusual lavas are characterised by remarkably low TiO2 contents, less than half the TiO2 content of the relatively unusual MORB that reach such high MgO olivine-rich compositions (Clarke, 1970). The King Is. Picrites (and by reasonable inference, the Yanac picrites) show pronounced LREE depletion (Waldron et al., 1993), indicating derivation from a strongly depleted peridotite source that had yielded one or more previous batches of tholeiitic basalt magma. Such second stage melts lacking LILE enrichment occur in some advanced continental rift settings as a component of seaward dipping reflector sequences erupted rapidly immediately before and during breakup (see Chapter 11).

The King Is.-Yanac picrites are petrographically dissimilar from primitive boninitic lavas that make up a substantial proportion of the lower section of the Cambrian mafic- ultramafic complexes of central Victoria (Heathcote greenstone belt) and western Tasmania (e.g. Heazlewood Complex). Orthopyroxene and clinoenstatite phenocrysts dominate boninites, but are unknown from the King Is.-Yanac picrites, which are solely ol-phyric.

10.4.2 Collider suite: Frying Pan prospect

Core from the Frying Pan prospect was supplied by CRAE. These were all altered mafic rocks, some with unusual "ball" textures typical of low-Ca boninites. In thin section, they are highly vesicular, with a high modal percentage of altered glass, indicating an extrusive origin. Serpentine-talc-chlorite pseudomorphs form after orthopyroxene (enstatite?), minor twinned clinopyroxene (probably dinoenstatite) up to several millimetres in length, and deep red chromites occur as phenocrysts. The phenocryst assemblage is plagioclase-free, indicating an ultramafic origin. The groundmass is replaced by messy talc-serpentine after what appear to be orthopyroxene microlites. All these features are associated with low-Ca boninites (A. J. Crawford, pers. comm.). 236 Only four samples were selected for standard wholerock analysis due to the limited amount and extremely altered nature of the material available. Major and trace element data are given in Table 10.4.1, recalculated volatile free. LOI's ranged from 7 to 14%, consistent with the degree of serpentinisation these rocks have undergone. Selected major oxides and trace elements are plotted (Figures 10.4.2, 10.4.3). Also plotted for reference is a field for Tasmanian MUMC, from the 510 ± 6 Ma Heazlewood Complex (Turner et al., 1998), and the Magnet mine. The data for this field are from Brown (1986).

The geochemical data for the Frying Pan metabasic lavas show the two major compositional features of boninites, namely relatively high Si0 2 at high MgO, and very low TiO2 contents (Figure 10.4.2), supporting the petrographic assignment.

In summary, the Frying Pan metabasic lavas are altered boninites, which are of restricted occurrence, and by inference, are confidently correlated with very similar rocks forming parts of the mafic-ultramafic allochthon in Victoria and Tasmania (Crawford et al., 1996a; Crawford & Berry, 1992)

10.4.3 Post-collisional suite: Mt Stavely Volcanics, McRaes Prospect (Black Range), Mt Dryden Belt, VIMP-3 & -8

Three main belts of "greenstones" crop out west of the Moyston Fault in western Victoria, from east to west, the Mt Dryden Belt, the Mt Stavely Volcanic Complex, and the Black Range Belt. No data on the compositions of the latter rocks are available, but extensive unpublished data exists for the Mt Dryden Belt (Crawford, 1982) and the MSVC (Crawford et al., in prep). In addition, Buckland & Ramsay (1982) provided analyses for the MSVC. The MSVC, dated at 500 ± 2 Ma (Crawford et al., 1996b), is dominated by medium- to high-K calc-alkaline andesite, the Fairview Andesitic Breccia, with a prominent felsic lava unit (the Narrapumelap Road Dacite) at the top of the sequence. These lavas show strong age and compositional similarities to the Mt Read Volcanics in western Tasmania (Crawford et al., 1996b). In contrast, the Mt Dryden Belt consists of a very well-preserved sequence of medium-K calc-alkaline andesites and dacites with relatively low TiO2 contents (-0.5% at 60% Si02 cf. 0.8% for MSVC and MRV) on Mt Dryden itself, and more felsic lavas with microdiorite plugs occurring further south at Bellellen (see Figure 10.1.3).

Based on (1) the age and compositional similarity with the MRV, which unambiguously post-dates emplacement of the forearc-derived ophiolitic allochthons in western Frying Pan Sample FP1 FP3 FP4 FP6 Rock UM lava UM lava UM lava UM lava Si02 52.47 52.96 54.84 61.64 TiO2 0.31 0.16 0.26 0.12 Al203 13.10 10.35 11.25 8.80 Fe203 11.07 9.79 8.77 8.04 FeO* 9.96 8.81 7.89 7.23 MnO 0.16 0.23 0.13 0.14 MgO 14.31 18.16 14.80 15.56 CaO 5.66 6.72 5.90 4.47 Na20 1.13 1.21 0.81 1.15 K20 1.72 0.37 3.19 0.05 P205 0.07 0.03 0.05 0.03 LOI 10.12 14.02 7.10 10.81

Y 8.1 5.5 7.5 3.9 Rb 20.4 5 43.6 <1 Ni 429 358 376 428 Cu 54 25 57 23 Pb <1.5 7 <1.5 3 Zn 75 64 60 52 Nb 1.3 1.8 1.7 1.6 Zr 28 38 25 32 Sr 122 160 111 118 Ba 648 135 859 10 Sc 36 23 33 19 V 199 99 178 90

Ti 1867 978 1549 743 Zr/Ti 0.01 0.04 0.02 0.04 NbN 0.16 0.33 0.23 0.41

Table 10.4.1 Whole-rock analyses recalculated volatile-free for the Frying Pan suite ss • 60

0 Cl) 55

50 10 15 20 25

0.35 -

0.30 - •

0.25 -

0.20 - o 17- 0.15 -

0.10 -

0.05 -

0.00 10 15 20 25

10 15 20 25 14 - • 12 - • 10 -

2 -

10 15 MgO 20 25

Figure 10.4.2 Major oxide variation diagrams, Frying Pan Suite Field for Tas MUMC from Brown (1986) 237 Tasmania and Victoria (Crawford & Berry, 1992), and (2), the occurrence of fault slices of boninite-derived serpentinised ultramafics in the MSVC, it is assumed here that the MSVC is also a post-collisional magmatic suite.

The Mt Dryden belt remains undated, but regional geological considerations (e.g. it is conformably overlain by Late Cambrian Glenthompson Sandstone) suggest that these lavas too are a post-collisional suite.

In this study, lavas drilled in VIMP-3 & 8, and in the Black Range are compared with those in the MSVC and Mt Dryden Belt.

Maher et al. (1997) reported analytical and petrographic data for andesitic lavas drilled in VIMP-3 (Jalumba domain, Miga SZ) and VIMP-8 (Ni Ni domain, Dimboola SZ). The Jalumba domain is believed to be a strike continuation of the Black Range Volcanic Belt. On the basis of limited geochemical analyses (5), both packages of rocks were correlated with the outcropping Mt Dryden Belt. The Mt Dryden Belt has been correlated with the post-collisional MSVC (Buckland, 1987; Crawford et al., 1996a). In this section, VIMP-3 & -8 samples are compared with samples from McRaes Prospect in the Black Range, and data from outcrop samples from the Mt Dryden Belt.

Petrographically, both the VIMP samples are prehnite-pumpellyite grade rocks with variably intense ab-ser-epi-qz ± carb, pump, chl alteration. Relict plag and cpx (augite) phenocrysts and vesicles are preserved in an altered glassy matrix with microlitic plag VIMP-8 samples are often autobrecciated plag ± cpx-phyric andesite to dacite lavas with glassy matrices. Overprinting sil-chl-carb vein alteration appears to be of hydrothermal origin (Maher et al., 1997).

Twelve samples were obtained from CRAE for the McRaes Prospect at the southern end of the Black Range Belt. These include 3 from GM46 (72.8, 96.2, 115.8 m), 5 from GM47 (70.8, 156.7, 182.0, 204.5, 227 m) and 4 from GM48 (41.3, 82, 96.2 & 170 m). Petrographically, these range from plag ± cpx-phyric dacite (6 samples) through to plag ± qz-phyric rhyodacite (4 samples) and plag + qz-phyric rhyolite (2 samples). Of the relict phenocryst phases, plagioclase was usually albitised and sometimes sericitised; cpx altered to chl-epi ± clz; and FeTi oxides to leucoxene. Carbonate and silica alteration were also present. This assemblage indicates lower greenschist metamorphic conditions. 238 Thirty-one thin sections from CRAE drillholes HS 1198, 1199, 1200 & 1201 from various localities in the northern Black Range were also examined. The dominant rock type from these holes were cpx + plag-phyric andesite lavas (16 samples). Next most common was cpx- or cpx + plag-phyric basalt lavas (6 samples) and plag-phyric andesites (3 samples). The remainder were an assortment of plag + qz-phyric rhyolite, plag + ksp-phyric rhyodacite, trachyandesite breccia, and basalt. Phenocryst assemblages and primary textures such as vesicles are preserved, although primary glass is devitrified and altered. Basaltic rocks tend to be altered to an assemblage of epi-ab-chl-carb, whereas andesitic rocks were altered to chl-ser-ab-carb-qz. Both assemblages indicate probable prehnite-pumpellyite fades, with actinolite absent.

For the Mt Dryden Belt, 8 samples provided by the GSV and 14 samples acquired by the author were petrographically examined. Localities sampled include Mt Dryden (6 samples), Bellellen (8 samples), Barton-Jallukar (5 samples) and Mt Elliot (3 samples). Mt Dryden samples include cpx-plag ± qz, bio, ap-phyric andesites, plag + qz-phyric dacites and qz-phyric rhyolite. All contain glassy groundmass indicative of lavas. Alteration of cpx to epi-chl-act and plag to ab-ser indicate greenschist facies metamorphism. Bel!ellen samples include plag-cpx-il ± qz-phyric diorites with act-ab- ser-epi alteration, and plag + cpx + opx-phyric diorites or gabbro (GSV samples) altered to ser-pre-chl-epi-ab-leuc. Opx, probably hypersthene, is always altered to chl; cpx appears to be in places autometamorphically altered, and in others burial metamorphosed, to actinolite. The samples from the Barton-Jallukar area include plag + cpx-phyric basaltic andesites lavas and shallow intrusives, a plag + qz-phyric rhyodacite intrusive, and a highly altered aphyric lava of uncertain composition. Alteration assemblages in the identifiable samples include pre-chl-epi-clz ± qz, pump, signifying prehnite-pumpellyite fades metamorphic grade. The unclassified sample is an act-ab-qz-chl rock of greenschist grade, and may have been contact metamorphosed. Finally, Mt Elliot samples are plag + cpx ± opx-phyric andesite lavas with altered glassy groundmasses. Alteration includes chl-pre-ser-ab, also indicating prehnite-pumpellyite facies metamorphism.

From the available samples, four lavas and four intrusives from the Mt Dryden Belt, consisting of one basaltic andesite from Mt Dryden; basaltic andesite, two diorites and rhyodacite from Barton-Jallukar; two diorites from Bellellen; and andesite from Mt Elliot, were chosen for wholerock analysis. To these were added a rhyodacite from GM 46; dacite, rhyodacite and rhyolite from GM 47; 2 dacites and a rhyodacite from GM 48; and a dacite breccia (4137813) from the Black Range Volcanics. All samples were prepared and analysed in accordance with procedures outlined in Chapter 4. 239

Volatile-free major and trace element data for these rocks are given in Table 10.4.2. LOI's ranged from 1.29 to 5.39 %, averaging 2.64%; this reflects the well-preserved nature of most of these samples, despite metamorphism to prehnite-pumpellyite or greenschist facies. Major oxides and trace elements are plotted in Figures 10.4.4 & 10.4.5. The field for Mt Stavely rocks is taken from data in Crawford (1982).

Clear magmatic trends are visible in FeO*, Al203, P205 and probably in TiO2 and MgO. FeO* and TiO2 give the most useful information; the decreasing trend of both elements with increasing Si02 is indicative of calc-alkaline fractionation. Fractionation in TiO 2 appears to indicate two parallel liquid lines of descent: one for the VIMP samples, Mt Dryden belt intrusives and all but one of the Mt Dryden lavas; and a more Ti enriched line for the Black Range samples and a rhyodacite from the Barton-Jallukar area. MgO has a similar, but more scattered appearance to T10 2. All of these trends are probably due to fractionation of cpx and Fe-Ti oxides, including ilmenite, as observed in the BelleIlen samples. Low TiO2 (< 1%), observed in all samples, is typical of post- collisional calc-alkaline suites (Crawford & Berry, 1992) sourced from refractory mantle associated with prior boninitic magmatism. Decrease in CaO and Al 203 with increasing Si02 is probably indicative of ongoing plagioclase fractionation. P205 displays a very interesting pattern: P, an incompatible LILE, builds up in the melt producing apatite until dacite composition (Si02 = 65%) is reached. At this point apatite is removed from the melt, and the P concentration drops off rapidly in more felsic end-members. This is consistent with the observation of ap-phyric andesites with Si02 c.62% from Mt Elliot.

In summary, rocks from VIMP-3 and -8, the Black Range and the Mt Dryden Belt have strong affinities with each other. They are calc-alkaline rocks ranging in composition from basaltic andesite to rhyolite. Two magmatic series are apparent: one generating the Mt Dryden Belt and VIMP rocks, the other generating the Black Range Volcanics. Both suites have been correlated with the 500 Ma calc-alkaline MSVC, which is a post- collisional suite (Donaghy, 1994; Crawford et al., 1996a). Data presented here confirm these findings.

10.5 Chromite Geochemistry

Chromian spinels are regarded as reliable indicators of the tectonic setting of eruption and emplacement of their host mafic and ultramafic rocks. Microprobe analysis of chromian spinels was undertaken to determine the affinities of two of the serpentinised rock suites from the Glenelg Zone: serpentinised harzburgite from VIMP-6; and Mt Dryden Belt Locality Barton Barton Mt Elliot Dryden Barton Barton Bel!ellen rock bas-andesite rhyodacite andesite andesite diorite diorite diorite Si02 61.11 75.47 61.71 56.64 60.17 60.10 58.31 TiO2 0.46 0.38 0.52 0.47 0.58 0.57 0.39 Al203 15.29 11.36 15.68 16.23 15.69 15.54 14.06 Fe203 7.18 3.05 6.59 8.97 9.23 8.42 8.79 FeO* 6.46 2.75 5.93 8.07 8.30 7.57 7.91 MnO 0.08 0.04 0.11 0.13 0.11 0.13 0.14 MgO 2.20 1.37 4.30 5.82 3.74 3.13 6.11 CaO 10.45 2.28 6.69 7.58 3.72 5.35 7.47 Na20 2.97 2.51 3.06 3.23 4.84 5.31 3.36 K20 0.15 3.47 1.22 0.86 1.70 1.31 1.24 P205 0.10 0.07 0.12 0.07 0.22 0.14 0.11 LOI 4.31 1.33 1.83 1.88 2.64 2.18 3.11

Y 23 19.2 12.1 14 14.5 16.7 10 Rb 13.4 86.6 33.7 23 39 27.8 28 Ni 50 12 34 59 14 21 34 Cu 73 25 60 21 59 96 93 Pb 7 8 5 2 3 5 2 Zn 62 33 56 60 68 78 78 Nb 3.1 7.4 2.5 1 2.3 3.8 1 Zr 80 164 83 42 78 102 52 Sr 39 251 884 185 246 128 343 Ba 48 824 192 130 255 215 143 Sc 26 10 23 34 23 25 27 V 205 81 183 301 311 243 224 Ti 2763 2251 3114 2813 3453 3430 2358

Zr/Ti 0.03 0.07 0.03 0 0.02 0.03 0 NbN 0.13 0.39 0.21 0 0.16 0.23 0

Table 10.4.2 Whole-rock analyses recalculated volatile-free for post-collisional suites Mt Dryden Belt Macraes Prospect, Black Range Locality Bel!ellen GM46(115.8) GM47(70.8) GM47(156.7) GM47(227) GM48(82) rock diorite rhyodacite dacite rhyodacite rtwolite dacite Si02 58.96 74.18 75.04 76.89 62.72 75.67 TiO2 0.41 0.50 0.34 0.30 0.86 0.52 Al203 12.95 12.95 12.42 11.72 15.39 11.89 Fe203 9.19 3.53 2.93 2.56 7.08 3.54 FeO* 8.27 3.18 2.63 2.30 6.37 3.19 MnO 0.14 0.09 0.04 0.03 0.13 0.11 MgO 6.73 1.65 3.21 1.02 4.49 3.76 CaO 7.01 0.58 0.32 0.79 3.12 0.32 Na20 3.29 6.33 4.60 5.64 2.12 3.88 K20 1.20 0.08 1.03 0.98 3.99 0.18 P205 0.11 0.12 0.07 0.06 0.11 0.12 LOI 2.48 1.29 2.18 1.30 4.81 2.36

Y 11 18 14.3 13.5 23.2 11.7 Rb 30 1 17.4 6.2 63.6 2.7 Ni 45 8 15 7 26 5 Cu 90 - 16 42 6 64 230 Pb 2 2 2 2 9 6 Zn 74 77 72 15 98 128 Nb 2 2.6 2.3 1.6 4 2.6 Zr 54 125 116 114 131 113 Sr 331 77 66 102 81 112 Ba 166 35 236 171 522 61 Sc 25 14 8 7 25 10 V 234 51 64 33 157 54 Ti 2461 2988 2025 1820 5129 3138

Zr/Ti 0 0.14 0.16 0.12 0.17 0.22 NbN 0 0.04 0.06 0.06 0.03 0.04

Table 10.4.2 Whole-rock analyses recalculated volatile-free for post-collisional suites (cont.) Macraes Prospect, Black Range Locality GM48(96.2) GM48(170) 4127813 rock dacite rhyodacite dacite bx Si02 72.63 79.66 64.20 TiO2 0.60 0.41 0.66 Al203 13.39 10.45 15.32 Fe203 5.82 2.86 6.80 FeO* 5.23 2.57 6.12 MnO 0.17 0.04 0.14 MgO 3.71 1.09 6.46 CaO 0.33 0.72 2.33 Na20 1.91 4.23 3.80 K20 1.29 0.51 0.17 P205 0.17 0.04 0.14 LOI 3.71 1.37 3.73

Y 12.5 13.1 13.8 Rb 19 7.9 2.4 Ni 8 6 47 Cu 193 29 94 Pb 10 9 11 Zn 261 57 373 Nb 2.4 3 3 Zr 114 99 115 Sr 67 134 263 Ba 382 83 365 Sc 13 9 14 V 90 34 132 Ti 3605 2430 3949

Zrai 0.19 0.23 0.22 NbN 0.03 0.04 0.03

Table 10.4.2 Whole-rock analyses recalculated volatile-free for post-collisional suites (cont.) 18 Lalk. Tonalite

0 c.1 14

12 Cpx And • A 0 10 1 55 65 75 55 65 75

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Key: diamonds = Dryden belt lavas squares = Dryden belt intrusives triangles = VIMP 3 & 8 lavas crosses = Black Range lavas

Field for MSVC from Crawford (1982)

Lalk. tonalite = Lakaldarno Tonalite, MSVC CpxAnd = cpx-phyric andesites, MSVC

55 65 S102 75

Figure 10.4.3 Major oxide variation diagrams, Black Range & Dryden Belts, and Mount Stavely Volcanic Complex 8-v- 25 - • X 7 - • CpxAnd NarDac 20 - 6- • t 'E 5 - C. ? 15 - E. X X a 4- ' X x a *A, •A 12 X z3 __ ›- 10 • M SVC X - A X< • • . A 2- m a ' A A X 5- • 1 - • 111

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6000 - 180 - 160 - 5000 - 140 4000 - 120 _ FL • loo — a 3000 C. r 80 - N 2000 60 - A Ala 40 - • 1000 - 20 - 0 I 1 I 0 50 100 150 200 0 10 20 30 Zr (ppm) V (13Pm)

Figure 10.4.4 Trace element variation diagrams, Black Range and Dryden Belts, VIMP, and Mt Stavely Volcanic Complex

Field for MSVC from Crawford (1982) Key as for Fig.10.4.4 NarDac = Narrapumelap Road Dacite, MSVC CpxAnd = cpx-phyric-andesites, MSVC 240 serpentinised ol-rich lavas from Yanac South. In the case of VIMP-6, determination of a tectonic setting helps determine the position of the boundary between the Glenelg and Stawell Zones. For Yanac South, chromite geochemistry can confirm affinities with rift-related basalts and King Is. picrites.

Chromites in polished thin sections from both bodies were analysed for selected major oxide compositions using the University of Tasmania's Cameca SX-50 electron microprobe. Some 17 chromian spinels from the Yanac South picrite suite and 50 spinels from VIMP-6 were analysed. Data are shown in Table 10.5.1. Data for Cr 203 and TiO2 and Cr# v Mg# are plotted in Figure 10.5.1.

The two suites are distinguishable on the basis of their Cr203 and TiO2 contents. Yanac South spinels have intermediate Cr203 (35-55 13/0) and Cr# (50-70), and very low Ti02, consistent with the interpretation of the Yanac South rocks as part of the break-up association immediately prior to development of oceanic crust. Further similarities with King Is. will be explored in Chapter 11.

VIMP-6 spinels have higher Cr203 (c.60%) and show two populations in Cr#, both in equilibrium with highly refractory mantle peridotite sources. Both have Cr# > 80, strongly suggestive of a boninitic fore-arc like the Tasmanian MUMC (Arai, 1994; Crawford & Berry, 1992). These confirm that VIMP-6 is part of the collider association, and indicate that this slice should be included in the Dimboola SZ rather than the Stawell SZ. In theory, this implies that the Moyston Fault should pass to the east of VIMP-6; however, it is still possible that VIMP-6 has intersected a detached horse of footwall rocks within the fault zone.

10.6 Conclusions: the external "collisional zone" of the Delamerian Orogen.

Brown et al. (1988) were the first to relate the geophysical anomalies of the southeast Australian lineament system to a specific plate tectonic model for the development of the Adelaide and Lachlan Fold Belts. Their 1988 study on aeromagnetics was followed by companion studies on the gravimetric signatures (Murray et al., 1989; Anfiloff, 1990; Murray & Scheibner, 1990).

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VIMP-6 Grain 229.8-7 232.5-10 232.5-9 MgO 7.45 7.94 8.29 Al203 7.25 7.27 7.51 S102 0.03 0.00 0.04 TiO2 0.03 0.01 0.01 Cr203 61.52 60.36 60.30 MnO 0.53 0.42 0.48 FeO* 23.01 22.77 21.91 Fe203 1.87 2.72 2.42 Fell° 21.32 20.32 19.73 Mg# 38.45 41.11 42.88 Cr# 85.06 84.78 84.35

Table 10.5.1 Major oxides from individual spine! grains, VIMP-6 & Yanac South (cont.) 90 01ipees... 80 •

70 •

20 30 40 50 60 70 80 Mg#

Figure 10.5.1 Discriminant diagrams, Cr-spinels, VIMP-6 & Yanac South Key: squares = Yanac Sth; diamonds = VIMP-6 Fields from Crawford & Kamenetsky unpublished data. Boninites are Hunter Ridge & New Caledonia. 241

• Deposition of the Kanmantoo Group and equivalents ("Kanmantoo Fold Belt") at a continental margin. • Cambrian development of a west-facing volcanic arc ("Stavely belt") at the western margin of the "Victorian microcontinent", including east-dipping subduction of oceanic crust between the craton and the arc. Development of intra-oceanic arcs (Heathcote & Mt Wellington greenstone belts) further east. • Late Cambrian-Early Ordovician convergence of the "Victorian microcontinent" and the craton culminating in the Delamerian Orogeny. • Renewed continental margin sedimentation into the Lachlan "basin", floored by the "Victorian microcontinent" and oceanic crust to the east. The source of this sediment was the Delamerian orogenic welt.

In this scheme, the Heathcote & Mt Wellington greenstones were believed to have been emplaced onto the "Victorian microcontinent" during the assembly of the LFB during the Benambran and Tabberabberan events.

This sequence of events appears largely consistent with much of the evidence now available. However, some features of the model are now in need of revision. First, this study (Chapter 9) shows that the Kanmantoo Group and the Teltawongee Group (both elements of Scheibner's (1972) "Kanmantoo Fold Belt") are probably not equivalent units, and that only the NSW rocks can claim to represent the continental margin. Also problematical for the above model is the finding of this study that the "Stavely belt" is a composite feature including thrust slices of an intra-oceanic arc, post-collisional volcanics, and possible continental margin rift volcanics. The Mount Stavely Volcanics themselves rocks do not constitute fragments of an island arc.

A major deficiency of the above model is the necessity of the "Victorian microcontinent", both as a rift block and as a collider. While the presence of a continental fragment at depth under the LFB is still possible (see for example Ci-awford & Direen, 1998), recent geophysical evidence from eastern Australia suggests that such a block must be very small, and is probably not responsible for the fold-and-thrust deformation observed in the Delamerian Orogen.

Kennett and co-workers (Kennett, 1998; Kennett et al., 1998a,b) have produced seismic tomographic models of eastern Australian which suggest that the fast wavespeeds indicative of cratonic lithosphere cease abruptly at 140-141 0 E. This line lies well to the west of the suspected position of the "Victorian microcontinent", and 242 must be considered a significant piece of evidence against the existence of such a body.

Such evidence is not surprising in the light of recent models for the occurrence of slices of boninitic fore-arc rocks and Late Cambrian submarine, post-collisional calc- alkaline volcanics within the external zones of the Delamerian Orogen (Crawford & Berry, 1992; Crawford & Direen, 1998; this study). These features suggest that the collider was in fact an intra-oceanic arc, rather than a rigid continental indenter, and that post-orogenic magmatism was submarine. The concept of an arc collider pre- dates the microcontinental model, and has been advocated for both the Antarctic and southern Australian sectors of the Ross-Delamerian orogen (Weaver, 1984; Gibson, 1987; Flottmann et al., 1994) as reviewed in the previous chapter. Structural and deep crustal seismic studies in the LFB (Gray et al., 1991; Cox et al., 1991; Gray & Willman, 1991a,b) confirm the thin-skinned character of the LFB, and emphasise Siluro- Devonian duplex development in an oceanic crustal underplate underlying much of the LFB. All of these lines of complementary evidence suggest a Late Cambrian "West Pacific" style of collision (cf. New Caledonia) which did not produce massive orogenic relief and its isostatic consequence, major lithospheric thickening.

In terms of tectonic elements, the Glenelg Zone compares more favourably to the Koonenberry Fold Belt than the more internal zones of the Adelaide Fold Belt (see Chapter 9). Similarities include: • continental rift-margin sequences including the magmatic break-up association (Yanac South, Peebinga-1 volcanics, and possible SDRS under the Dahlen domain) • continental margin clastic wedge (Glenelg River Complex) • arc-related collider associations (boninitic slices in the Ni Ni and Kalkee domains) • post-collisional volcanic suites (MSVC; Black Range & Mt Dryden Volcanics; slices in the Ni Ni and Kalkee domains) • west-vergent Cambrian thrust geometry • overprinting Silurian thrust deformation • cratonisation by the Devonian.

These features tend to suggest that these two regions may have originally been continuous parts of the external Delamerides. This contrasts with the interpretation of Brown et al. (1988), which correlated the KFB with more internal zones of the Delamerian Fold Belt, on the basis of the present "zig-zag" pattern of aeromagnetic lineations. 243

In support of the proposed new correlation, Kennett (1998) pointed out that the structures of the lithospheric mantle bear little resemblance to the break-up patterns inferred from the present distribution of supracrustal geophysical features. As alluded to above, the lithospheric mantle shows a very simple linear transition from cratonic to accreted elements at c. 1400-141 °E, which is interpreted as the response of the lithosphere to the rifting process. Because the magnetic and gravity lineaments are definitively supracrustal features, and relate to multiply-folded rocks as demonstrated throughout this study, it must be the case that the latest elements of deformation must be removed before earlier palaeogeography can be restored. In particular, if the effect of Carboniferous mega-shear (see Chapters 6 & 8) is removed from the Koonenberry- Scopes Range Trend, and also the second bend in the vicinity of Renmark (SA), a possible Silurian fold-belt geometry would be restored. The approximately linear form of this belt then mirrors the lithospheric structure. However, before real matching can take place, removal of the effects of Silurian and Cambrian coaxial shortening must also be effected. In the absence of detailed strain and fault kinematic data, which are beyond the scope of the present study, it is proposed that the amount of shortening from both deformations amounts to no more than the width of the zone of transitional wavespeeds between the craton edge and the thin, slow crust of the eastern Tasman Fold Belt System (after Kennett et al., 1998a).

In summary, similarities of the tectonic elements within the Glenelg Subzone of western Victoria, and the Koonenberry Fold Belt, suggest a closer correlation than that implied by earlier work. The two belts may have in fact been the contiguous external collision zone of the Delamerian Orogen, a hypothesis supported by consideration of lithospheric structural data, and oroclinal restorations based on new data from this study. 244

Chapter 11 Tectonic Significance of ?Neoproterozoic mafic rocks and sedimentary sequences, east coast of King Island, Tasmania 11.0 Introduction 11.1 King Island: Location and Geological setting 11.2 Regional Geology of King Island. Prior Work. 11.3 Study Methods 11.4 Structural interpretation and geophysical modelling 11.5 Geochemistry and tectonic affinities 11.6 Tectonostratigraphy 11.7 Implications & Conclusions. 245

Chapter 11 Tectonic Significance of ?Neoproterozoic mafic rocks and sedimentary sequences, east coast of King Island, Tasmania 11.0 Introduction

A detailed geological, geochemical and geophysical investigation of the ?Neoproterozoic Grassy Group including a conformable volcanic package on the east coast of King Island has the potential to clarify previously contentious tectonic relationships between King Island, Tasmania and western Victoria.

Earlier studies (Waldron et al., 1993) have shown that the King Island mafic volcanics are divisible into three stratigraphic and geochemical suites: a thin package of lower tholeiite submarine lavas and volcaniclastic rocks; an unusual assemblage of submarine and subaerial picritic lavas and hyalobreccias; and a thick upper sequence comprising tholeiitic lavas and volcaniclastic conglomerates.

The occurrence of voluminous, tholeiitic and picritic lavas in association with an evolved basaltic intrusive suite and transgressive marine sediments within the Grassy Group in a strike-continuous belt that extends from Macquarie Harbour to Phillip Island, is strongly suggestive of a rifted passive margin. Picrites are rare in the upper parts of the crust, and are thought to be the primary magmas that give rise to other melt types (e.g. tholeiitic basalts) by fractionation (Duncan & Green, 1987). As primary magmas with highly mafic compositions and high densities, they rarely reach the surface except in exceptional circumstances such as extensive rifting (Sparks et al., 1980; Huppert & Sparks, 1980). Therefore the occurrence of picrites on King Island also warrants further investigation, with implications for the tectonic linkages between King Island, Tasmania and mainland Australia.

Possible tectonic linkages have broader ramifications for the breakup history of the Rodinian supercontinent, and its passive-margin geometry (Direen & Crawford, 1998a).The study outlined below compares the King Island sequence with those examined elsewhere along the Late Neoproterozoic Gondwana margin.

11.1 King Island: Location and Geological setting.

King Island is the largest of the western Bass Strait islands. It lies between latitudes 0 39 30'S and 40° 10' S, and is centred on meridian 144 ° E (Figure 11.1.1).

230"-E 40 50 60

0 o CD co

Z z E § 8 s 0 o co co S s

0 N

0 o CO co

230"m E 40 50 60

Figure 11.1.1 King Island. Grid is AMG zone 55 246 Its tectonic relationship to southeastern mainland Australia has recently been clarified by the production of the magnetic anomaly map of Australia (Tarlowski et al., 1996) and the gravity anomaly map of Australia (Morse et al., 1992), which for the first time combine the Bass Strait geophysical data with data for the Australian mainland and Tasmania (Figure 11.1.2). These data show that major high-amplitude, low-frequency magnetic anomalies run approximately parallel to the west coast of Tasmania.

On the SoreII Peninsula near Macquarie Harbour (Figure 11.1.2), these anomalies are associated with a pile of tholeiitic volcanics called the Double Cove Volcanics which are geochemically correlated with the latest Neoproterozoic Crimson Creek Formation of western Tasmania (A. J. Crawford, unpublished data).

South of King Island, the anomaly bifurcates, with the higher amplitude, longer - , wavelength component wrapping around the eastern side of the island (Figure 11.1.2). The western edge of the anomaly clips Bold Head, on the south-eastern corner of the island, where a thick pile of ?Late Neoproterozoic tholeiitic volcanics is exposed.

From Bold Head, the anomaly passes back into Bass Strait and continues on a north- northeast trend towards Westemport Bay, terminating at Phillip Island (Figure 11.1.2). At this location, metabasalts, metadolerites and cumulate rocks have recently been recorded (Henry & Birch, 1992).

Thus there is a strong spatial association between the major high-amplitude, low- frequency magnetic anomaly passing through Bass Strait with piles of tholeiitic basalts. An outstanding question of interest is the nature of the relationship between these basalts, and tholeiitic volcanics of the Kanunnah Subgroup in the Smithton Trough on the northwestern Tasmanian mainland (Waldron et al., 1993; Brown, 1989)

11.1.1 Topography. Land use. Access.

On King Island, a network of sealed primary roads connects the coastal townships of Grassy, Currie and Naracoopa, with well-formed unsealed roads giving access to the interior. Access to the coast away from the townships is via poorly formed tracks, some of which are only negotiable by four-wheel drive vehicle.

King Island has generally low relief, rising to a maximum of only 180 masl. The interior is covered by Quaternary sand dunes, stabilised by grass and low vegetation. These Figure 11.1.2 TMI image of western Tasmania and Bass Strait

Note continuation of high-amplitude magnetic anomaly from Macquarie Harbour (M) via eastern King Island (K) to Philip Island (P)

140 142 144 0 0 247 conditions make the interior viable for dairy and sheep farming, to which use most of the island is turned over.

The ?Neoproterozoic-?Lower Cambrian sequence lies on the east coast between Currie and Naracoopa, 40 minutes drive from the main township of Currie.

11.2 Regional Geology of King Island. Prior Work.

The geology of King Island has recently been reviewed by Turner et al. (1998), Waldron et al. (1993), Brown (1990) and Turner (1989).

The oldest known rocks on King Island are a polydeformed series of quartzites, quartzo-feldspathic and pelitic schists, rare marbles and orthoamphibolites which outcrop on the north and west coasts of the island (Figure 11.2.1). These were affected by an early (but undated) episode of isoclinal folding before they were intruded by two separate granite plutons of the Cape Wickham Granite late during folding (Cox, 1989). Samples of granite have yielded Late Proterozoic SHRIMP U-Pb zircon dates of 760 ± 12 Ma (Turner et al., 1998), and Rb-Sr dates of 743-753 Ma (Cox, 1973). Intrusion of the granites produced a further generation of (generally brittle) deformation of the metasedimentary package, and metamorphosed parts of them to homblende hornfels facies. The multiple phase first deformation event dated at 760 ± 12 Ma has been termed the Wickham Orogeny by Turner et al. (1998).

Late-phase dykes around both plutons are deformed by a second generation of folds, and the granites are in places transected by mylonitic shear zones (Blackney, 1982). Cox (1973) recognised a further two generations of folding in the metasediments in the north, but in the southwest only one further deformation has been described (Blackney, 1982).

The base of the east coast section is a series of lower greenschist facies cross-bedded quartzites, interbedded siltstones, rare conglomerates and laminar siltstones. These are possibly correlates of the Rocky Cape Group of the northwest Tasmanian mainland. The relationship of these sedimentary rocks to those of the north and west coasts is unclear, but most authors have postulated a concealed angular unconformity running north-south through the centre of the island. The rationale for this appears to be that the older units strike dominantly northeast, whereas the ?Neoproterozoic- ?Lower Cambrian units strike north-south. This proposed unconformity would be Holocere Sand arid alluvium

Tertiary 1111 A lkali oiivine basalt ..n..estorte Lover Carboniferous- Fr73 Upper Devonian • Eocarnbrian - 1773 Volcanic - sedimentary Cambrian Precambrian Sillsione.saridetone f -1-:Guani1e E2- Schist, quartzite Figure 11.2.1 King Island Geology (modified from Waldron et al., 1992) 248 equivalent to that observed in northwest Tasmania between the Rocky Cape Group and its basement sequence (Baillie, 1989a).

Lying above the younger sequence with apparent unconformity is the Grassy Group (Brown, 1990). Despite an objection by Jago (1974) about the use of this name for rocks outside the Grassy "mine sequence", the usage of Brown (1990) clearly indicates that this is the correct name for the unmetamorphosed sequence at the coast (Brown, 1990, p 1175). The Grassy Group is a thin (<200 m), distinctive sequence of sediments, including Cottons Breccia, and unnamed laminar dolomite and siltstone formations.

Cottons Breccia, also referred to as a mixtite (Waldron et al., 1993), has been the subject of investigation by Carey (1947), Jago (1974) and Waldron et al. (1993). It contains depositional features possibly associated with glaciation, as well as density mass flow (Jago, 1974). This unusual association, despite being lithostratigraphically like the "Marinoan glacials" recognised in the Adelaide Fold Belt, and also like the Croles Hill mixtite (Everard et al., 1996) on the Tasmanian mainland, has so far eluded definite correlation (Waldron et al. 1993). The breccia sequence is overlain disconformably by a thin (< 15 m), laminated dolomite or dolomitic siltstone sequence.

Immediately above the capping dolomites of this sequence at City of Melbourne Bay lies the first volcano-sedimentary association. This is a sequence of low-Ti tholeiitic pillow lavas, tuffs and agglomerates, peperites and mudstones.

Between this and the picritic second volcano-sedimentary sequence is a well-exposed disconformity north of The Gut (Waldron et al. 1993). This association comprises picritic pillows and flows with interbedded breccias and resedimented hyaloclastite.

The upper volcano-sedimentary association occurs further to the south, arodnd Bold Head (Figure 11.2.1), and has not been found in depositional contact with the other sequences. Nevertheless dykes geochemically correlated with this sequence intrude the other two sequences, whereas it is only intruded by much younger (Cretaceous) lamprophyric dykes. These relationships indicate that the southern sequence is younger (Waldron et al. 1993). The sequence consists of porphyritic tholeiite lavas interbedded with a very thick volcaniclastic conglomerate containing lava-derived clasts. This sequence has been metamorphosed in places up to amphibolite hornfels grade due to proximity to the Devonian Grassy Granite (ibid.). 249 I propose the name Skipworth Subgroup to refer to the stratiform volcanic units of the Grassy Group, named for Skipworth Creek which flows in the type area between Naracoopa and Bold Head. The component formations of the suite are the City of Melbourne Formation ("lower tholeiites"), Shower Droplet Formation (picrites) and Bold Head Formation ("upper tholeiites"), all named for the best exposures of the different rock types. The evolved sills underlying the Skipworth Subgroup will be termed the Grimes Intrusive Suite

A graphic summary of the stratigraphic relationships in the Grassy Group is given in Figure 11.2.3. Waldron et al. (1993) discounted the possibility of correlations between the Grassy Group and Skipworth Volcanic Suite, and the Togari Group and Kanunnah Subgroup (Everard et al., 1996) of the Smithton Trough on the Tasmanian mainland. I question their findings, based on new evidence from geochemistry and lithostratigraphy presented below.

Mid Devonian granites intrude probable equivalents of the ?Neoproterozoic sequence near Grassy (Figure 11.2.1), where dolomite horizons have been metasomatised to scheelite-bearing skams (Brown, 1990). These granites are temporally related to the Devonian granites found in western Tasmania, and are associated with the Tabberabberan Orogeny.

11.3 Methods

In February 1998 an excursion was made to King Is., acquiring 289 samples at the locations shown (Figure 11.3.1). Mapping at aerial photo scale (approximately 1:16 000) was undertaken from Fraser Beach at Naracoopa to Grassy Bay. Due to the limitation of outcrop to a narrow coastal strip, usually < 100 m in width, map interpretations were extended using airborne magnetic data from AGSO. The map compiled from these sources is shown in Figure 11.3.2.

These interpretations were aided by the compilation of a magnetic susceptibility database comprising some 180 measurements. These were taken on outcrops in the field. The results are summarised in Table 11.3.1. Figure 11.2.3 Summary stratigraphic section, Grassy Group

— Top of Bold Head Formation continues offshore

— Bold Head Formation

000 VVVVVVVVVV 000

AAAAAAA —Shower Droplet Formation VVVVVVVVVVV City of Melbourne Formation + + ++++++ +

-\–Grimes Intrusive Suite Base Skipworth Subgroup Yarra Dolomite Member

Cottons Breccia

LEGEND

LITHOLOGY

SILTSTONE BRECCIA + +4- Sills Picrite flows VVV Tholeiite DOLOSTONE 000 Conglomerate Flows

245E 50 55 60

0 - r's

z I .,0 ,I3

0 - 0 CO CO

tO - ii, 10 Ul

245xE 50 55 60 0 5

km Grid: Australian Map Grid, Zone 55. Figure 11.3.1 Southeast King Island Sample Localities

, ••••.t

Key ' (2t ' C53 Devonian Granite v72.. F i • ''n"

/ Bold Head ,p,.. --F Formation ,F (conglomerate) s . 1I / Ft,_

/ Bold Head dpi .

. Formation m . ---., (volcanics) o Shower Droplet \* w Formation ns City of Melbourne 6q Formation

Grimes Intrusive dnw 5575"" 1 Suite

Grassy Group (undifferentiated)

Cottons Breccia F — — —F /\..N./•./\

Rocky Cape Group correlates

1 --.• , i ..... / / ....: / .F Fault

Inferred Boundary

F. F Mapped Boundary F 5570w • •-F Shower h , Droplet Coastline shown in white Rock I F

, Coastal mapping at c.1: 14000 by Nick Direen & Seb Meffre, February 1998. The Gut Previous mapping in Waldron et al (1993). 'city of Melb?vrne Units away from coastline interpreted from Bay aeromagnetic data, courtesy AGSO.

Grid is AMG Zone 54. F\

5 km 5565 A F / • F

/ / /

/ ./ 1,, / 1 1 \ F / / % / . t / . ' t / t / / 1 / I / I o • / F, r ! . ,

' v1 / 1 1 F 1 / 1 / 1 / •

5560000 255'

Figure 11.3.2 New geological map, Naracoopa to Bold Head, eastern King Island 250

Table 11.3.1 Magnetic Susceptibility of ?Neoproterozoic Rocks, East Coast, King Island

Stratigraphic Unit k (x 10-5 SI) Number of samples Rocky Cape Group equiv. 60 36 Cottons Breccia 25 12 Dolomite 40 24 Upper siltstone 25 12 Grimes Intrusive Suite 1000 41 City of Melbourne Fm 2200 41 Shower Droplet Fm 50 48 Bold Head Fm 5000 50

11.4 Structural interpretation and geophysical modelling

The geology of the east coast of King Island is divided into two structural packages, separated by an inferred unconformity (Brown, 1990). The lower sequence comprises folded siltstones and quartzites, and can be seen both inland at Pegarah, Lymwood and Lancaster Rd, and on the coast at Fraser Beach, Naracoopa and The Wall. These rocks contain both easterly and westerly dips (see Figure 11.4.1), and well-developed mesoscopic folds. They have a pervasive east-dipping slaty or spaced cleavage.

The geology of the east coast of King Island above the unconformity is structurally simple.

Evidence from pillow lavas, cross-bedding in dolomites and siltstones, flame structures and graded bedding all indicate that the sequence dips and youngs east to southeast. Stereonets of poles to bedding are shown in Figure 11.4.1. This suggests that the entire sequence occupies the western limb of a broad macroscopic syncline. No axial plane cleavage was observed in the sediments or volcanics above the Cottons Breccia.

This simply deformed, eastward-tilted sequence is broken up by a conjugate set of northwest- and north-northeast—striking faults (Figure 11.4.2). These have both dip- slip and strike-slip components, with apparent net dextral slip incrementing from north to south. Figure 11.4.1 Equal area stereonets of bedding and cleavage relationships, Grassy Group and Rocky Cape Group correlates

Bold Bold Bead Read-Cottona Creek

lector Mean. 50/140 actor Mean- 38/136 Spherical Variance- 0.04 Spherical Variance. 0.03 Calculated girdle: 49/276 Calculated girdle: 75/025 Calculated beta axis: 41-096 Calculated bate axis: 1540;

Cottons Ck-City City of of Melbourne Melbourne Bay Bay-The Gut

actor Mean. 39/117 actor Mean. 54/106 Spherical Variance. 0.02 Spherical Variance. 0.04 Calculated girdle: 72/004 Calculated girdle: 63/218 Calculated beta axis: 18-184 Calculated beta axis: 27-037

The Gut-Shower Shower Droplet Droplet Rock Rock-Raracoopa

actor Mean. 52/098 actor Mean. 53/269 Spherical Variance. 0.03 Spherical Variance. 0.43 Calculated girdle: 81/195 Calculated girdle: 90/005 Calculated beta axis: 9-015 Calculated beta axis: 0-11%5

Maracoopa Lower (picritos) Siltstones

actor Moan. 39/097 actor mean. 42/093 Spherical Variance. 0.08 Spherical Variance. 0.12 Calculated girdle: 66/334 Calculated girdle: 71/340 Calculated beta axis: 24-154 Calculated beta axis: 19-140

Figure 11.4.2 Rose diagram. Fault strikes in the Grassy Group

Faults East Omit Traverse

20 10 10 20

" I I

lax Variance. 0 Resultant. 0.72 Circular Stil.Dev.. 4 Mani= .25.0%

16 Pt. Figure 11.4.3 TMI western Bass Strait with line of modelled section indicated

E144 ' E144 30' E145'

co o

TMI pseudocolour image with shading from the southeast Figure 11.4.4 2-d magnetic model of Grassy Group, eastern King Island

10 750 • Ob s. Mag. _700 _650 rms error: 1.5 _600 Mshift: 0 6_ _550 _500 _450

l) _400 _350 w Ga _300 2u _250 au (m _200 ity sag ) v _150 _100 u (i Gra _50 _0 -6_ _ -50 _-100 -8_ _-150 _-200 _-250 0 •• rassy Gp• •• rou •:-.!:Ni\;:. N NN 4 1000 1000_ • • •• • • r, . • • • ass am lasaits:.: . • • • • ••• •••••• • • • • . i.•.•.•. . \ :\s,„ •••••••••••••••••••••••••••.:‘•• 2000_ • •:•••••••• 2000 t, • • • • • E • • • • •• ••• 15.a'S.'a.lt*E• •• • ••••• ••••• I ••• • • • • . . . I. • • • • • c. 4boOxfC5-5 ••••••• •••••••• •.. •••••••••••••••••••••••••• • • • • •.•••••••••• • • • 04 • • • • • .• .•I •••••••••••• • • • • • •• • • • ••• ••••• • • 4e 3000- •••••••• • • • • • • • • • • • • • • • • • • 3000 • • • • • • • ••••••••••••••••••••••••••• • •• •. • • • • • • • . • • • • • • • • •.• • • c.6200x10-5 •• • • • • •• •• •• • •••• • • •• • • . • . • . • . • • • • • ••••••••• • • • • • • • • • • • • • • • • • . • . • • • • • • • • • • • • • • • • • • • • • • • • • •. •• .• •• .. •• .. •• • • • • • • • • • • • • • • • • • • • • • • • • • • 4000 4000_ • • • • • • • • • • •••.•••••.••••••••••••••.•+•.•••• • rote rozoic • • • • ••••••••• 4. • ••• •• •.• • .•••• • ••• •• • •• ••• •• ••• •• •• • •• ••• • •• • • • • • • • .:•:•:•:•:::: •••••••:-:-• • • • • • • • • ••• •• • • • • •• • • • • • • • • • • • • • • •• •• • • • • • ••••• • • • • ••••• • .• • .• .•. ••• • •• • • • f• 5000 •••• • ••••• 1. • • • 5000

-5000 5000 10000 15000 20000 25000 30000 35000 Distance (m) 251

The major northwest-southeast trend is identical to normal down-to-the-southwest faults in the Otway Basin (Bouef & Doest, 1975) and normal down-to-the-northeast faults in the Bass Basin (Gunn et al., 1996). North-south and north-northeast trending faults are parallel to transfer faults in the Bass Basin (Gunn et al., 1996). Willcox (1990) showed that northwest-trending structures in the Otway, Bass and Gippsland Basins acted as strike-slip faults during pre-Late Jurassic extension that opened the Eyre Sub-Basin during Australian-Antarctic breakup. Early Cretaceous extension reactivated these faults as normal structures, while forming nearly orthogonal transfer faults between the subsiding blocks. Thus the brittle faults observed on the east coast of King Island are probably related to Late Mesozoic rifting.

To determine whether the Skipworth Subgroup is responsible for the major magnetic anomaly observed offshore, a two-dimensional magnetic forward model was constructed. Magnetic data were extracted from aeromagnetic coverage owned by AGSO. These data are a composite of two surveys. The first, covering the offshore areas, is 1966 vintage data, and was flown at a height of 3548 masl, with flight lines spaced at 19200 m. The along-line sample interval in this survey is 60 m. The second survey, flown in 1987 covers King Island and immediate offshore areas. It was flown 250 masl with 1500 m line spacing and 20 km tie lines. Sample spacing in this survey is also 60 m. Both surveys were flown with E-W lines. The stitched survey was re- gridded using a 100 m cell size and reduced to the pole by AGSO.

The forward model was constructed using Model 2d v3.1a, with modelling assumptions as per the discussion in chapter 4. The line of section is shown in Figure 11.4.3, and the model shown in Figure 11.4.4. The petrophysical properties outlined in Table 11.3.1 were used as constraints.

The magnetic field, artificially smoothed by the gridding process, consists of three main features. At the western end of the line is a long-wavelength (Al2 =10 km) 650 nT high (assuming a local base level at -150 nT). Between 10 km and 22 km is a second high- amplitude 550 nT anomaly. The eastern "tail" of this anomaly is overprinted by a 100 nT high of 7 km half-wavelength.

All three highs have been modelled with significant offshore thicknesses of the Bold Head Formation dipping at c. 700 southeast. The modelled thickness of c.22 km occurs in two packages which are likely to be fault repetitions of the same unit, repeated by a suspected thrust. The true thickness of the individual packages is estimated to be 252 between 8500 m and 13200 m. These estimates differ slightly from those published in Direen & Crawford (1998a) for the same modelled section; the earlier model used a body assumed to be Cretaceous syenite to model the low-amplitude high at the eastern end of the line.

The non-magnetic section to the west of the line generally represents the magnetic low associated with the deformed metasediments beneath the Grassy Group. However, it must be noted that the entire apparent thickness of the Grassy Group (including the City of Melbourne Formation) crops out in the line of section between 2400 m and 3100 m; its contribution is negligible, due to the non-magnetic nature of the thicker sedimentary section relative to the c.200 m of volcanics exposed. The City of Melbourne Formation (which forms the shore platform) may be responsible for the western inflection on the slope of the main 600 nT magnetic high.

The unmodelled non-magnetic components within the basaltic piles probably represent thicker (up to 800 m) sections of less-magnetic volcaniclastic sediments; volcaniclastic conglomerates exposed at Bold Head have a minimum thickness of 400 m. Farther to the east, non-magnetic wedges which thicken eastward are believed to represent the contribution of Jurassic-Recent sediments of the Bass Basin which onlap King Island. The wedge between 6 and 13 km is probably a ?Cretaceous fault-controlled trough between reactivated older faults.

11.5 Geochemistry and tectonic affinity of the mafic volcanic sequences 11.5.1 Wholerock geochemistry

A total of 239 petrographic thin sections were examined from the collection made on King Island. Most samples have excellent preservation of primary phenocryst phases, groundmass and textures, despite metamorphism up to greenschist facies. The "syenite" sills of Waldron et al. (1993) are actually differentiated gabbroic sills up to 30 m thick, which have 01-enriched cumulate bases, and more fractionated upper portions that are cpx + plag + Fe-Ti oxide-bearing gabbro to leucogabbro. These compositions are quite unlike syenite, and I have adopted the use of the terms "evolved sills" or "sill complex" to refer to these rocks. The City of Melbourne Formation comprises plag + cpx-phyric tholeiitic basalts and dolerites, often altered to ab-act-chl- carb ± epi , with dolerites retaining primary ophitic textures. The Shower Droplet Formation consists of chl-altered ol ± cpx, crt-phyric picrite lavas and dykes. Cpx is mainly augite or titanaugite, and is often rimmed with secondary actinolite. Quench textures are well-preserved in these samples. The Bold Head Formation is composed CV C\ICIDCONC000,-Ps et 0 Ul Ps 13 to to CI T.- Tr nr r- 13 -0 Ch ct et T- a) 0 u) e- 0 et. T- C: CO CD CV to CD NY CP C C oi to oi c\i 6 Ti 6 6 c5 6 6 Ti 00 T- y- y- CV CD up y- d ine m

CD Ps OD CD OD CD Ch 0 et cn OD CD Cl et CV et CV CO CO CO 0) et 13 13 Ch CV CV Cr) ter CD Ps Ul CO OD CV CD Ul et C) T- cn OD Ul CO Ol et CV CD C C oi oi ui

Tr de

Ci Ci ei e4 6 u5 6 to 00 c4 t to y- T- y- no d = n T- a) CV CD CD T- 'CV r- Tr T (0 .- CV CV CV OD CM QD OD Ch CV ts 73 13 CV Ch 01 CV 0 Ps OD CM OD CV CD QD C) et m- r- C) 01 Ul 01 et et CD r- C C 6 ui 6 ui c‘i c5 Ti c4 6 6 (5 ui c5 6 cq y- Tr to T-

0) 0) toCO 0) 0) to o N a, to et CO CD T- r- r- 01 CO CD 13 13 r- CD et CO CO N CIODNCVCOPs N 00 CV OD CO et et et CV CD C: C 6 6 6 up O c5 ci ui c5 u5 6 Ti c5 6 y- T- Tr y- up y- y-

OD CO T CD CV Ps et CD C) OD OD Ol CV CV Ch to to 0 ts to 13 1.0 C0 Ch Ps CO 13 CV CD Ch CD T CM CM 11/ T CV 00 co CO et CD Ul nt CI C: 4,2 ui c 0 e4 Ti c5 6 r: Ti 6 6 UP 1y- y-

mt NI' 0 1:1- C•7 0 0 N CO 0 NCOCDOCICOV,-(1707,-1-V CO N CO N (7) N 0 cf: a) CO 1:1' Cr) to (11 N C N co" co' C T- c5 Ti oi 6 ui ui 6 6 T- N r T T up y- y-

co NocoNNN co co N co co lf) CD 17 CD N N. 17 Cr) CI) 0 III *0 • .cr a, CD al 1- CO CO Cf) 1- 0 N C (C) •cr N 1(7 N C CO N. c • 6 Tr: 6 cri c5 co 6 Ti 6 6 '- up T- T-

CD CV CO CA al Ps C) OD Ps Ps a) CO CV 0 73 Ul CI Ch Ps CO T 1/ CV OD Ch CD 13 ps et Ps CD CI et CD CO CV CD Ul Ul et C CO CD r- Tr Tr T- c: to to os c 6 6 Ti c5 c5 6 c5 c4 T- 6 '- Tr T 1- to co e- r-

Ol CD Ps CD CO CO CD to CO CO CD et et 0 CV CD CD OD CD et CD CD 1- ts CO 1- CM 13 er P, CO CV OD CV CM et CD 0 CD OD to CD et CV et er CD Ps CD us 4 c cq 6 6 ui oi 6 6 6 ui 6 6 y- Tr up T- y- y-

OD Tr op CD e- to OD 01 OD OD CD CO 01 73 Ps T- CD 01 CV CV 13 CV T- r- CV 73 73 Ps Ps CO CO Ps CV CD Ul OD CD CD cl OD C OD Ul et LO CO et C CD CD as as CC O 6 ci to 0 to r: to 6 6 y- T T up 1- T

CO Ps CD Cf) et et 0 et CD 11) 03 • Ul 73 QD up r- OD CD CD et T- CD OD 73 1- 13 Cr) co co to Olto 0) CD 00 7 Tr c .,- Tr cm Tr T- CV a) Ps QD ui C 4,6 c Ti c5 c4 T c5 ui u5 ui 6 6 y- 1- CV Cr) up T T T

T- CQ et T- CO CV Ch CV CV OD CD CD 17 CO N lf) 0 N CD 13 CO CO N CO NV CV Ps CD a) CD CV Ch 7 r- CD CD CI C CD LO CO LO N C 1- co ai d co c '-0 04 Ti oi c5 ui y- oi c5 6 oi to I-

0 to cmc`lacn 0 4,00N00—00 0 0 cm c,`DI w c al as cm 0 es Z NG CL -J CC CO CO 1■71 Uri (5 e) fi 8 Shower Droplet Fm Rock Flow Flow Pillow Flow Flow Flow Breccia Pillow Flow Dyke Flow Hyaloclastite Sample R15702 R33032 R33033 R15732 R15734 R33031 R33027 K25 K40 K104 K77 R33041 S102 48.43 46.01 49.36 48.67 44.59 52.79 46.30 47.29 48.15 50.90 49.01 50.15 TiO2 0.23 0.35 0.22 0.27 0.30 0.23 0.28 0.31 0.66 0.29 0.33 0.26 Al203 8.86 10.91 8.31 8.68 12.15 5.61 12.04 13.66 8.35 12.23 12.20 8.93 Fe203 8.46 9.64 8.90 10.31 12.54 9.56 10.96 11.06 9.96 8.61 9.44 9.67 FeO* 7.62 8.67 8.01 9.27 11.28 8.60 9.86 9.95 8.96 7.75 8.50 8.70 M nO 0.18 0.18 0.16 0.17 0.20 0.23 0.15 0.17 0.13 0.18 0.17 0.29 MgO 21.31 21.30 22.56 21.08 21.13 18.67 22.98 18.25 23.94 9.53 14.09 17.50 CaO 12.17 11.35 10.25 10.09 8.41 12.61 6.98 7.00 8.48 16.20 13.87 12.45 Na20 0.32 0.23 0.20 0.36 0.34 0.26 0.26 . 2.22 0.17 1.96 0.65 0.58 K20 0.01 0.01 0.01 0.35 0.35 0.02 0.02 0.04 0.10 0.10 0.22 0.15 P205 0.02 0.02 0.02 0.03 0.00 0.02 0.02 0.01 0.06 0.01 0.02 0.03 LOI 3.98 4.66 4.61 3.06 15.27 2.75 6.72 5.25 6.13 3.14 4.86 3.09

Rb 3 2 nd 10 8 3 nd nd 3 1 13 5 Ba 17 16 14 375 541 17 11 22 4 81 59 125 Th nd nd nd nd nd nd nd nd nd nd nd nd Sr 3 4 4 11 9 6 17 26 7 46 12 19 Zr 11 15 10 6 8 13 12 9 30 10 12 14 Y 7 12 7 12 15 7 10 13 11 13 12 6 Sc 33 38 28 38 38 31 34 34 25 38 28 22 Ni 772 738 1213 769 873 566 893 904 893 352 222 786 Cr 1650 1627 2347 2610 2460 1710 2440 3504 2191 1104 4759 1701 V nd nd nd nd nd nd nd 196 153 198 185 nd Cu 13 11 33 47 44 37 89 nd nd nd nd 21 Zn 47 49 42 56 67 60 53 nd nd nd nd 50 La 0.2 0.2 0.3 0.2 0.3 0.3 0.4 nd 2.8 nd nd 1.3 Ce 0.2 0.5 0.6 0.5 0.8 0.7 0.8 nd 6.5 nd nd 2.8 Nd 0.7 0.8 0.7 0.6 1.0 0.6 0.9 nd 5.0 nd nd 1.9 Nb nd nd nd nd nd nd nd nd 4.6 1.0 2.0 nd Table 11.5.1 Whole-rock analyses for the Skipworth Subgroup recalculated volatile free (cont.) Grimes Intrusive Suite Bold Head Fm Rock Gabbro Cumulate Leucogab. Gabbro Leucogab. Cumulate Leucogab. Flow Dyke Flow Dyke Flow Flow Flow Sample R33003 R33002 K3 K152 K153 K167 K168 R33029 R33022 R33025 R15697 K50 K55 K58 Si02 58.69 62.67 64.10 57.53 60.28 44.96 48.54 50.22 48.80 47.76 47.32 47.42 46.80 49.28 TiO2 0.64 0.69 0.73 0.99 0.70 0.22 0.28 1.76 0.80 0.86 0.76 1.70 1.41 1.77 Al203 15.07 15.45 15.80 14.39 16.22 8.51 15.09 14.57 15.33 18.13 20.17 15.94 15.32 13.74 Fe203 7.47 6.21 6.69 7.82 7.27 12.13 9.27 14.69 12.49 9.70 8.61 13.48 12.70 15.13 FeO* 6.72 5.59 6.02 7.04 6.54 10.92 8.34 13.22 11.24 8.73 7.74 12.13 11.42 13.62 MnO 0.13 0.10 0.17 0.15 0.12 0.14 0.15 0.20 0.15 0.16 0.14 0.22 0.20 0.22 MgO 6.89 3.54 5.51 6.03 6.71 29.90 15.64 6.65 8.28 9.47 8.40 7.14 10.49 6.77 CaO 5.40 4.69 0.66 7.41 1.62 3.63 9.15 6.58 9.97 10.64 10.35 9.84 9.52 8.38 Na20 3.29 2.94 4.10 2.19 3.55 0.29 1.12 4.92 3.06 2.25 2.50 3.38 3.27 4.29 K20 2.29 3.56 2.10 3.35 3.43 0.12 0.73 0.26 1.01 0.93 1.69 0.61 0.13 0.25 P205 0.12 0.12 0.12 0.12 0.12 0.09 0.03 0.15 0.09 0.10 0.07 0.28 0.17 0.16 LOI 3.42 2.44 4.02 9.31 5.42 1.84 2.31 3.64 3.15 2.47 3.57 1.69

Rb 103 98 35 86 66 9 30 13 55 29 61 23 4 6 Ba 619 550 795 506 637 16 124 118 170 378 665 271 88 148 Th nd nd 13 8 9 3 3 Sr 110 213 93 185 86 7 80 165 735 182 700 222 240 156 Zr 127 156 198 150 179 24 35 85 60 40 52 97 93 102

Y • 25 32 32 34 32 8 11 24 20 9 14 23 22 30 Sc 25 23 25 31 29 23 25 40 43 34 32 41 45 44 Ni 51 14 88 34 181 1069 203 79 134 162 199 96 291 76 Cr 125 58 2090 74 1288 3087 670 144 282 398 492 173 659 72 V 143 127 162 306 176 112 125 379 323 202 197 369 297 397 Cu 19 14 nd nd nd nd nd 110 130 52 58 nd nd nd Zn 62 66 nd nd nd nd nd 105 74 51 47 nd nd nd La rid nd 35.7 22.3 30.8 4.1 4.3 7.6 • 4.0 10.1 3.4 21.1 17.6 7.8 Ce nd nd 79.3 56.6 65.1 5.4 8.3 15.6 8.5 20.6 8.6 43.8 41.4 17.0 Nd nd nd 35.7 28.4 28.2 2.0 7.0 13.6 6.1 10.5 5.7 19.0 17.6 11.6 Nb nd nd 15.6 12.7 14.0 2.3 3.6 nd nd nd nd 32.3 19.1 7.6

Table 11.5.1 Whole - rock analyses for the Skipworth Subgroup recalculated volatile free (cont.) A 25 - A 60 A 20- X A Kanunnuah Subgp A ge 15 - A:iox A • 255 • • • • 8 • a 01 10- < • MIME A 50 • X • • • A • . 5 - XXXx • • • 45 . 0 I 1 I 0 5 10 15 20 25 30 0 10 20 30

4.0 - 19 - 3.5 - 17 - 3.0 - 15 - F2.5 - 5 - • 01 IL 11 - A LA, • IN 1 .5 - 9 - 4- LI RE S m 1.0 - XII 7- am • 6/1 0.5 - A A NAN! ID A 5 0.0 II I III 0 10 20 30 0 5 10 15 20 25 30 MgO

Figure 11.5.1 Major element variation diagrams, Skipworth Subgroup

Key: • triangles = Grimes Intrusive Suite; diamonds = City of Melbourne Fm; squares = Shower Droplet Fm; crosses = Bold Head Fm

Field for Kanunnah Subgp from Crawford (unpublished data). 200 p 5000 180 A 4500 160 4000 140 3500 •-•• 120 g3000 ii. 0. 100 Ot 2500 rti 80 a 2000 60 1500 40 1000 20 A 500 0 0

0 10 20 30 5 10 15 20 25 30

60 - 1400

50 - 1200

40 - 1000 g 800 o. a. 2. 600 20 - 400 X. MA • ii 10 - ■ I. 200 X all ION A o o 5 10 15 20 25 30 o 10 20 30 MgO

5 15 25 MgO

Figure 11.5.2 Trace element variation diagrams, Skipworth Subgroup

Key and field for Kanunnah Subgp as in Fig.11.5.1 Grimes Intrusive Complex 1000 -

- Gabbro sills 100

io -7. ....

• ...... ------.------"------■-- , 1 - ... • • - - ...... - - - ' - - ... - • " - - 0.1 - Cumulate base

0.01 Th Nb La Ce P Nd Zr Ti Y

City of Melbourne Fm.

1000 -

100 —

10 — Pillowed flows 1 -

0.1 -

°to Th Nb La Ce P Nd Zr Ti Y

Bold Head Fm. 1000 —

100 —

10 — Lava flows

1 -

(11 -

0.01 Th Nb La Ce P Nd Zr Ti Y ,

Figure 11.5.3 N-MORB normalised spidergrams, Skipworth Subgroup (normalising data from Sun & McDonough) 253 of cpx- or plag + cpx-phyric dolerites and basalts with the alteration assemblage ab- act-ser-epi-carb, indicating greenschist facies metamorphism. More detailed petrographic and fades analysis of these formations can be found in Waldron et al. (1993).

Seventeen samples were chosen for standard whole-rock X-Ray fluorescence analysis using the Philips PW1410 spectrometer at the University of Tasmania School of Earth Sciences. These samples comprised 2 sills from the Grimes Intrusive Suite; 3 flows and 3 dykes from the City of Melbourne Formation; 5 picrite flows; and 3 flows and 1 dyke from the Bold Head Formation. Samples were carefully chosen to avoid alteration, following procedures outlined in Crawford et al. (1997).

Major and trace element data for the four suites are shown in Table 11.5.1. These data are recalculated volatile free, with loss on ignition values reported separately. Also included are 15 analyses from Waldron et al. (1993), and a field for lavas and dykes from the Kanunnah Subgroup of the Smithton Trough (A. J. Crawford, unpublished data). Major and trace element data are plotted versus MgO in Figures 11.5.1 / 11.5.2.

The reason for this geochemical study is to compare the Skipworth Subgroup tholeiites with those in the Late Neoproterozoic sections in northwestern Tasmania, rather than to present a detailed petrogenetic study of the King Is. rocks; the latter task has already been undertaken by Waldron et al. (1993).

In both major and trace elements, the lavas from the Kanunnah Subgroup display some overlap with the Skipworth Subgroup, but with a tendency to being more evolved. In the trace elements, particularly in Zr and Y, the Kanunnah Subgroup plots closest to the Bold Head Formation.

The Grimes Intrusive Suite splits into two groups. Two samples with high MgO are thick cumulate sills with abundant ol and crt; these plot closer to the Shower Droplet Formation, which they resemble mineralogically. The remainder of the sills are far more evolved and show elevated Zr, Y and Nb at MgO -8%. This suggests a relatively early timing for these sills which are not found intruding the other formations. N-MORB normalised element patterns for 3 samples of evolved Grimes Intrusive Suite (Figure 11.5.3) show significant negative Nb anomalies, strong LILE and LREE enrichment suggestive of the involvement of significant crustal contamination of this magma, or alternatively, derivation from metasomatised refractory subcontinental lithospheric mantle. SOReJ OILUOM ale Sill Alleopiewoiyoi os paleinotepai Med Pue Ilad dnoAqns womdpis `suleJ6 puicis lenpimpul wcui saw° Jolew z .9•1.1. awl 0081. 9Z11. ZO'61. SO'LZ L6*ZE Z178 61:61. 8661. VE'8 LZ'VZ VO'l-Z 91.'SZ 9Z'9Z Oiled L81 1-81 9E8 96171. 61717L 6Z1 698 ELT 88'Z L9*Z ELT DYE COZed 6 V1.9 Z6'89 ZE*09 91711Z 0902 0E817 V9•917 LV*1.9 Zt'VE 6ETV WEE 99*ZE #61A1 891.9 01719 99 .95 9Z'EL L6' L L 81779 LE' L9 9L'E9 209 9t799 Z819 6609 n't9 #00 91796 ZZ'L6 86 86176 C996 01716 V916 Z916 8 L' L6 6L'L6 E986 917'86 17E86 siejoi 60.93 6Z*VZ 68' 9Z Z9'0V L0917 8617Z C6'9Z 8E*ZZ 17 6' OZ E6'9Z 9E'EZ L61Z L6'LZ .0ed 0 9Z'O Ll 0 EE*0 1.91. LO*0 61:0 LO*0 L *0 ZE'0 i70Z'O Lz"o 8Z'O OLIN 617'Zt EtZt 6Z'6E 8EVE 8t*ZE 89'Et L81 .t' VE917 61:9V ZO'LV L9*EV 961E 17 0t EOZ-10 WO z9.0 EEO 0817 LV-9 8V-0 890 990 6170 L1:0 1.90 890 L9*0 ZOLL 00•0 1.00 00•0 L0'0 ZO*0 1.0•0 ZO'0 E0'0 000 000 CO*0 ZO'0 0E0 ZO*0 vcro 1.10 1.0•0 E0'0 900 ZO*0 600 900 Z L*0 900 L0'0 900 ZOIS LEL L Z0'81. 91:0Z 1.98 91:9 L911. CELL C811. CO*OZ L L'ZZ VC' LZ 8t717Z 09*ZZ COZIV 6901. CE'll 1.W0 I. VO'9 LL 'Z 890I. znn EE6 L6'0 L CI. L Zt7'6 01. *L L8'9 061A1 L*8 99LN L 99LN L*9 99LN 1:9 99LN L't 99LN Z1. 991.N 1: I. 99LN L 9 EN 9 EN Z* V EN V EN C EN upo

860Z 690Z I.Z*ZZ 99*ZZ 0171 L L8'0Z ZE*9 L 89'ZZ 13Z'VZ 999S81. 9E91. LZ'91. 801-Z Oiled OCT 9V.Z 9EZ 176T 68' I. V9*Z 1-9'Z 69*C 99*Z C8*Z 6L1- ZE'E COZed 6E'tb 917'9t7 996E 69017 82.179 91:1717 61719 99017 81:9E 6Z* L9 L999 L91.9 LV*117 #61A1 L91.9 Et'69 6869 9819 9689 1.8*V9 9Z19 0899 a'ss OL1.9 1.9*89 Z689 61:Z9 #-10 E8*86 817'86 8E16 L986 V1:86 9E16 8086 L086 OL'L6 L896 179'L6 6C*86 Z L16 sIeoJ 90'EZ 1.6'ZZ 8917Z OE'9Z 01:61. 9Z*EZ L981. 1.8'9Z 69*9Z L LZ E811. 8811. LO'n .0ed LZ*0 OZ'O LE*0 9Z*0 81:0 CZ•0 Cl- '0 81.0 090 17Z*0 900 9Z*0 17I:0 OulAl 1.1:917 99•Th 98•Et 9Z*68 9Z'Sti 9ti I. V 8E117 9V'Ot 9Z'O9'0t' ZV'6E 9917 1.6917 L688 EOZ-10 E9'0 890 L9*0 V9'0 6Z'O 91:0 OZ*0 960 96'0 6Z'0 OV*0 1.9*0 ZOLL ZO*0 170•0 000 000 ZO'0 ZO*0 00•0 1.0•0 000 000 1700 1.0*0 000 0e0 91:0 171.'0 LO*0 900 980 90•0 600 900 800 ZO*0 660 170*0 C0'0 ZOIS LE*61. OVOZ 0L6 I. 9V•7Z C LZ Z6*ZZ EZ*ZZ 1761.Z 98* LZ LEVZ E9' LZ Lb' I.Z L6*EZ EOZIV 666 L9'6 9Z'8 ZL*9 Z811- 9Z' 6 8E*Z L L9'8 6E1 9601. tZ*Z L EY? L 917'6 1.'? EN I. EN 1.'1. EN 6 E9LN 8 E9LN L E9LN 9 E9LN Z*9 C9 LN 9 E9LN C9LN Z*Z E9LN Z E91.N L EMI ems enisrului sawn Grimes Intrusive Suite Shower Droplet Formation Grain K16610 K16611 k16612 K1042 k1043 k1043.1 K1044 K1045 K1047 K10410 K10411 K10414 MgO 8.39 8.56 9.98 15.29 14.84 15.13 15.13 15.08 15.28 14.55 14.57 15.18 Al203 10.63 10.73 17.14 25.40 23.55 24.63 24.01 23.80 27.27 23.64 22.18 25.14 S102 0.70 0.60 0.02 0.17 0.12 0.11 0.12 0.11 0.06 5.85 0.07 0.07 CaO 0.06 0.03 0.03 0.05 0.11 0.07 0.01 0.02 0.00 1.48 0.03 0.04 TiO2 2.95 3.10 0.50 0.17 0.16 0.14 0.14 0.14 0.17 0.18 0.36 0.20 Cr203 41.65 41.62 41.47 41.34 42.65 41.81 42.20 42.50 39.41 37.20 44.59 41.00 MnO 0.30 0.29 0.10 0.09 0.02 0.14 0.16 0.10 0.11 0.18 0.16 0.14 FeO* 31.78 31.98 27.55 16.17 16.15 15.80 15.55 15.61 15.81 14.51 16.62 15.67 Totals 96.46 96.91 96.81 98.69 97.59 97.83 97.32 97.35 98.11 97.59 98.57 97.44 Cr# 72.45 72.24 61.88 52.19 54.86 53.25 54.11 54.51 49.23 51.35 57.42 52.25 Mg# 39.03 39.59 48.27 68.30 67.70 68.54 68.97 68.83 68.32 56.70 66.26 68.85 Fe203 9.34 9.65 9.42 3.92 3.91 3.80 3.79 3.81 3.53 -5.88 3.77 3.80 Fell° 23.38 23.29 19.08 12.65 12.63 12.38 12.13 12.18 12.63 19.81 13.23 12.25 Shower Droplet Formation Grain K40 2.1 K40 3.1 K40 5.1 K40 6.1 K40 8.1 K74 chr1 K74 chr2 K74 chr2.2 K74 chr3 K74 chr4 K74 chr5 K74 chr5.1 K74 chr6 MgO 17.02 16.54 16.08 15.75 15.63 11.47 15.12 15.33 15.52 14.74 14.77 14.62 14.69 Al203 22.16 29.17 24.88 21.99 23.53 25.37 24.33 25.18 24.56 24.52 25.48 25.04 23.54 Si02 0.17 0.08 0.13 0.13 0.11 0.29 0.10 0.13 0.12 0.09 0.09 0.13 0.11 CaO 0.00 0.01 0.01 0.01 0.07 0.06 0.07 0.00 0.05 0.12 0.01 0.02 0.05 TiO2 0.43 0.44 0.59 0.49 0.48 0.14 0.16 0.19 0.15 0.19 0.17 0.14 0.16 Cr203 44.42 35.17 39.82 43.59 40.92 39.19 42.13 41.00 42.64 41.70 39.92 41.37 42.47 MnO 0.11 0.09 0.12 0.10 0.08 0.60 0.11 0.08 0.09 0.09 0.08 0.07 0.13 FeO* 13.50 16.40 16.82 16.73 16.31 20.32 15.77 15.65 15.85 16.09 15.71 15.71 16.28 Totals 97.82 97.91 98.45 98.78 97.12 97.43 97.78 97.57 98.98 97.53 96.22 97.11 97.43 Cr# 57.36 44.71 51.78 57.08 53.85 50.89 53.74 52.21 53.81 53.29 51.24 52.57 54.76 Mg# 76.21 72.37 71.11 70.58 70.68 53.17 68.60 69.19 69.44 67.16 67.68 66.67 67.20 Fe203 4.48 5.72 5.75 5.58 5.27 2.56 3.81 3.86 4.08 3.59 3.49 2.97 3.88 Fell° 9.47 11.26 11.65 11.71 11.56 18.02 12.34 12.17 12.18 12.86 12.57 13.03 12.78 Table 11.5.2 Major oxides from individual spine! grains, Skipworth Subgroup (cont.) Shower Droplet Formation Grain K74 chr7 K74 chr8 K77 chr1 K77 chr2 K77 chr3 K77 chr5 K77 chr6 K77 chr7 K77 chr8 K77 chr9 K77chr12 K40 1.1 MgO 14.86 14.95 14.43 12.80 12.00 8.28 13.46 5.94 12.96 13.10 15.00 15.23 Al203 24.25 25.09 24.21 20.56 23.14 17.10 21.83 21.88 23.53 23.64 24.87 26.89 Si02 0.12 0.14 0.11 0.12 0.12 0.08 0.11 0.14 0.10 0.09 0.08 0.09 Ca0 0.02 0.06 0.02 0.09 0.13 0.13 0.12 0.05 0.04 0.01 0.01 0.01 TiO2 0.19 0.15 0.20 0.18 0.20 0.19 0.19 0.17 0.20 0.23 0.21 0.50 Cr203 42.01 41.43 43.18 45.08 41.89 39.81 44.51 40.31 43.65 43.82 43.13 36.00 MnO 0.11 0.17 0.13 0.35 0.57 1.33 0.11 1.94 0.33 0.38 0.12 0.04 FeO* 15.87 15.79 15.96 19.71 19.82 30.93 17.64 26.87 17.59 17.63 15.14 18.63 Totals 97.43 97.76 98.25 98.90 97.88 97.85 97.98 97.29 98.41 98.88 98.55 97.39 Cr# 53.74 52.55 54.47 59.52 54.84 60.96 57.77 55.28 55.45 55.43 53.77 47.32 Mg# 67.64 67.69 65.47 59.34 55.97 40.81 62.24 29.53 59.60 59.89 67.50 67.94 Fe203 3.55 3.41 2.66 4.52 3.31 10.59 3.42 1.75 2.14 2.21 2.52 6.46 Fe110 12.68 12.72 13.57 15.64 16.84 21.40 14.56 25.29 15.67 15.64 12.88 12.82 Bold Head Formation Grain K60 chr 1 K60 chr 4 K6Ochr 1 K55 chr 1 K55chr 5 K55 chr 4 K55 chr 3 K55 chr 2 K55 chr 6 K55 chr 7 K55chr 7.2 K55chr 7.3 MgO 5.84 15.07 12.19 6.49 12.32 8.83 12.48 15.43 9.84 15.52 14.59 14.72 Al203 21.93 20.93 22.32 22.22 22.30 21.75 25.50 21.40 24.32 29.85 23.92 25.38 Si02 0.09 0.11 0.21 0.11 0.05 0.11 0.61 0.08 0.09 0.07 8.50 0.07 Ca0 0.00 0.03 0.03 0.05 0.01 0.03 0.12 0.02 0.04 0.06 2.57 0.00 TiO2 0.24 0.30 0.54 0.29 0.59 0.55 0.58 0.57 0.52 0.58 0.65 0.56 Cr203 38.32 44.87 39.13 37.57 38.36 39.83 35.97 43.63 38.12 32.86 32.62 38.57 MnO 0.50 0.09 0.50 1.32 0.18 0.20 0.25 0.18 0.23 0.11 0.11 0.06 FeO* 31.12 16.33 21.75 28.78 23.94 26.67 22.62 15.89 25.87 19.10 16.00 ' 18.23 Totals 98.05 97.73 96.67 96.85 97.75 97.97 98.13 97.20 99.02 98.13 98.97 97.60 Cr# 53.96 58.98 54.05 53.14 53.58 55.13 48.62 57.77 51.26 42.48 47.78 50.49 Mg# 28.42 69.05 56.75 31.93 56.84 41.71 55.73 70.38 45.36 67.86 52.33 66.12 Fe203 5.42 4.76 5.77 4.55 8.07 5.19 5.50 4.79 5.26 6.67 -8.55 5.32 Fe110 26.24 12.04 16.56 24.68 16.68 22.00 17.67 11.57 21.13 13.10 23.69 13.45 Table 11.5.2 Major oxides from individual spinal grains, Skipworth Subgroup (cont.) 70 - Scopus: boninitic

50 -

40 • 0 T.' 30 -

Yanac South 20 -

10 - anunnuah Iherzolitic

i i i 1 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 1102

Figure 11.5.4 Discriminant diagrams, Chromian spinels, Skipworth Subgroup

Key: diamonds = Grimes Intrusive Suite; squares = Shower Droplet Fm; triangles = Bold Head Fm.

Data are Direen, Crawford & Meffre (unpublished) Fields for Scopus Fm and Kanunnah Subgp are from Meffre (unpublished data) Field for Yanac South is from this study (see Chapter 10) 254

Both the Bold Head and City of Melbourne Formations show strong Fe-enrichment with fractionation, with the Bold Head Formation showing much stronger concomitant enrichment of Ti and Zr compared to the City of Melbourne Formation. Detailed trace element data given in Waldron et al. (1993) show that the strongly LREE-depleted picrites of the Shower Droplet Formation are not comagmatic with either suite of tholeiites. Figure 11.5.3 shows N-MORB normalised patterns for both tholeiite suites.

11.5.2 Chromite geochemistry

In addition to the wholerock data, 9 samples containing chromian spinels were selected for mineralogical analysis using a Cameca SX-50 electron microprobe. Samples were prepared according to procedures already outlined in Chapter 4. Of these, four were picrites, two cumulate sills, two upper tholeiites, and one a lower tholeiite. Selected major oxide data are shown in Table 11.5.2. Data are plotted in two discrimination diagrams (Figure 11.5.4). Also displayed in these diagrams are data from the Yanac South drillholes (see chapter 10) and fields for detrital chromites, representing potential repositories for volcanic detritus from the Late Neoproterozoic pile. These latter datasets are from the Smithton Trough on the northwest Tasmanian mainland (S. Meffre, unpublished data). The Late Neoproterozoic Kanunnah Subgroup samples are from volcaniclastics cropping out on the coast west of the Montagu River, on the western limb of the Smithton synclinorium (c.320000 mE, 5487400 mN). The early Late Cambrian (Idamean) Scopus Formation disconformably overlies the Kanunnah Subgroup; samples obtained from the Scopus Formation turbidites at Stony Point (c. 329000 mE, 5487600 mN AMG zone 55). This succession was mapped and dated by Baillie & Jago (1995).

Data from the King Island samples form a relatively coherent trend of low TiO 2 at intermediate Cr203 values, and intermediate Cr# (40 to 80) at a variety of Mg#, representing the less-evolved picrites to the more-evolved gabbroic sills. The observed Cr# values overlap with the primary chromite data from Yanac South, suggesting a similar moderately refractory peridotite source. Higher Cr# values (max. 78) in the sill complex may reflect derivation from refractory lithospheric mantle during the early stages of rifting. LILE enrichment and negative Nb anomalies in the wholerock data are consistent with this interpretation (Figure 11.5.3).

Analyses from the Smithton Trough form three distinctive groups; the first, found only in the Scopus Formation, are very low-Ti, high-Cr chromites believed to be derived 255 from boninitic MUMC to the south and east on the Tasmanian mainland. These analyses are quite unlike the King Island data. The second population includes analyses from the Scopus Formation and all but three analyses from the Kanunnah Subgroup, which have intermediate Cr# and low Ti, and closely resemble the King Island data. The third group, comprising three analyses from the Kanunnah Subgroup, are chromites with Cr# c. 25; these are derived from a fertile lherzolitic source (after Arai, 1994) unlike any reported from either King Island or the Tasmanian mainland.

11.5.3 Conclusions: affinities of the Skipworth Subgroup

Waldron et al. (1993) suggested that no direct one-to-one chemical correlation exists between the Skipworth Subgroup and the Kanunnah Subgroup, a finding supported by anomaly-tracing in the magnetic data. However, the close similarity of chromites from the Skipworth Subgroup with those found in the Kanunnah Subgroup and Scopus Formation, strongly suggest that the two packages were spatially linked during the Late Neoproterozoic to Late Cambrian. This link may have taken the form of a sediment supply system distributing detritus from exposed King Island basalts into the Smithton Trough. Such a link suggests a close proximity, perhaps of the order of the present separation, or less. Alternatively, the data can be interpreted to mean that picritic volcanism occurred at several locations along the east-facing rifted margin.

Everard (1998: unpublished data in prep.) described the petrology and geochemistry of the Spinks Creek Volcanics of the Kanunnah Subgroup. Three separate suites were described: a stratigraphically lower suite of high-Mg, low-Ti tholeiitic basalts, dolerites and gabbros; overlying moderate- to high-Ti evolved tholeiitic basalt lavas; and near the top of the sequence, mildly alkali picrites, basalts, dolerites and gabbros. The petrographic and compositional varieties within the Kanunnah Subgroup are thus very like that within the Skipworth Subgroup.

Despite the lack of direct geochemical similarity between King Island and the northwestern Tasmanian mainland, the proposed petrogenesis of suites of volcanics from both locations is essentially the same. This fact, combined with the implied spatial linkage from detrital chromite signatures, and the similar host sedimentary sequences, strongly suggests that the two complete packages are expressions of the same volcanic passive-margin forming event. Similar packages of tholeiitic and picritic rocks with minor crustally-contaminated lower sequences form components of voluminous Seaward Dipping Reflector Sequences (SDRS) in well-studied volcanic passive margins (e.g. East Greenland-Vering Conjugate Margin, North Atlantic: Viereck et al., 256 1988; Gill et al., 1988; Rockall Margin: Morton et al., 1988). The striking similarity between the geochemistry of volcanics in northwestern Tasmania, King Island and western Victoria, and SDRS suggests that these may be a remnants of a much larger Late Neoproterozoic volcar4 passive margin- a hypothesis further strengthened by consideration of the tectonostratigraphy, as outlined below.

11.6 Tectonic Interpretation of Cottons Breccia

As mentioned previously, Cottons Breccia (Jago, 1974) has to this time defied undisputed classification and correlation. It has been speculated by various authors (Carey, 1947; Spry, 1962) that it is a tillite, and specifically correlates with the "Marinoan" glacial horizon (Elatina FormationNerelina Subgroup) of the Adelaide Fold Belt (AFB). Proponents of this view argue that the thin (5 20 m) laminated dolomite disconformably above the breccia is the equivalent to the Nuccaleena Formation of the AFB (e.g. Coats & Preiss, 1987).

Jago (1974) in defining the Cottons Breccia reviewed all earlier work, but found only equivocal evidence for a glacial origin, concluding that the formation was most likely a mass- flow deposit modified by glacial activity.

His work was revisited by Waldron et al.(1993) who argued that the Cottons Breccia should be referred to as a mixtite, due to minimal evidence for glacial origin. They recommended the use of the name Cottons Breccia cease, although the formation name is well-defined, and established in the literature. I therefore continue the use of the name, as it appropriately describes the formation proposed by Jago (1974), and no alternative formation name or type section was proposed by Waldron et al. (1993).

Mapping during this study, although focussed on the relationships of the volcanics above Cottons Breccia, also failed to reveal the presence of features definitive of tillite, such as faceted and striated pebbles, weathering rinds, and widespread provenance. Many pebbles and cobbles in the conglomerate may appear to be striated, but on closer investigation, these clasts are all carbonate that had been etched by weathering processes.

Limited sampling and petrography on stained sections showed a clast population • strongly biased toward limestone, with minor amounts of sparry dolomite, chert and siltstone. Limestone clasts include sparry laminar varieties as well as matrix intraclasts of micrite. Siltstone clasts show strong petrographic similarity to siltstones beneath the 257 unconformity, indicating local derivation by erosion. Dolomite clasts comprise two varieties, dolomicrite and sparry dolomite.

These characteristics confirm Jago's (1974) observation of formational intraclasts of earlier breccias and carbonates occurring within the Cottons Breccia. I concur with Jago (1974) and Waldron et al. (1993) in finding that the Cottons Breccia is most likely a mass-flow deposit rather than a glacial till.

This conclusion is made more likely by considering the general tectonic environment occupied by the Grassy Group. Unconformably beneath the Cottons Breccia lie folded rocks which were in part eroded to supply clasts to the breccia; this situation implies some tectonic uplift process. Immediately above the breccia lies a thin dolomite or calcareous mudstone containing relict oolite and pelletal textures, indicative of a shallow subtidal or intertidal environment (Waldron et al., 1993). Conformably above the dolomite are pillow lavas of the City of Melbourne Formation.

Discounting unpublished and unverified palaeomagnetic poles for the Cottons Breccia and the lower tholeiite suite (cited in Jago, 1981), this sequence implies uplift, erosion and inundation accompanied by volcanism -a sequence typically associated with the syn-rift phase of continental margin development (e.g. East Africa-Madagascar conjugate margin, Coffin & Rabinowitz, 1992). In this interpretation, it is possible that the Cottons Breccia represents material mass-wasted from a submarine normal fault scarp. Wasted material would include carbonate talus from the footwall of the fault on the next higher block of a stepping-down-to-the-east rift system (Figure 11.6.1). This could give rise to the "conglomerate-within-conglomerate" character of Cottons Breccia (cf. Jago, 1974), without requiring multiple sedimentary cycles. The almost entirely local derivation of clasts of the breccia also supports a fault scarp mass-wasting origin for this unit, as most fault segments tend to be < 15 -20 km in length (Leeder, 1995).

Proximity of the depositional environment to a rift flank is strengthened by the geochemistry of the Grimes Intrusive Suite. The mineralogical and incompatible element compositions of these sills have similarities to early, lithospheric melt batches which form intrusive swarms parallel to the developing rift axis (e.g. Mesozoic Cape Peninsula Dyke Swarm: Reid, 1990; Mesozoic Northwest African Rift Province: Bertrand, 1991; Palaeogene Voring Plateau: Viereck et al., 1988). The volume of such swarms is typically small, and precedes the eruption/intrusion of much larger melt batches caused by decompression melting of the up-welling asthenosphere (such volumes are here represented by the tholeiite and picrite suites). Because ongoing Figure 11.6.1 Detrital recycling in an active normal-fault system

West East A

A: Initiation of new faults in a seismically active area breaks up continental shelf sequences

B: Talus is deposited on the next fault block down-to-the-east

C: Further faulting disrupts unstable, semi-consolidated talus piles, producing new talus fragments and blocks of old talus on next fault block down-to-the-east 258 asthenospheric activity controls the position of the widening rift axis (Bott, 1995), early lithospheric melts might be expected to occur towards the rift shoulders -in the zone of maximum normal fault throw, and hence associated with fault scarp breccias and other mass-wasting products.

11.7 Implications; Conclusions.

The co-occurrence of thick breccia, laminar dolomite, evolved basaltic dyke swarms, picrite pillow lavas and a thick (> 6 km) pile of tholeiitic basalt on the east coast of King Island is strongly suggestive of a passive-margin rift sequence. Although undated, these rocks are readily correlated with the Togari Group and Crimson Creek Formation of the Tasmanian mainland, using lithostratigraphic, geophysical and geochemical criteria. Dykes correlated with the Crimson Creek Formation have been K-Ar dated at 588 ± 8 and 600 ± 8 Ma (Brown, 1986), and the Togari Group has been placed in the Late Neoproterozoic using isotope chemostratigraphy (Adabi, 1997; Calver, 1998). These rocks and their correlates are associated with a continuous high-amplitude, low- frequency magnetic anomaly running from southwestern Tasmania to coastal central Victoria, a strike distance of almost 500 km.

The age, sedimentary and volcanic facies, tectonic affinities and geophysical signature of these rocks are similar to that of the 586 ± 7 Ma Mt Arrowsmith Volcanics (Crawford et al., 1997; chapter 4) and Kara beds (Mills, 1992; chapter 4) package in western New South Wales. Although both packages have clearly undergone later reorganisation by faulting, folding and thrusting during Palaeozoic orogenic events, I suggest that they are part of one original volcanic passive margin sequence.

There is also a possibility that a poorly known sequence of pillow basalts from the Churchill Mountains of southern Victoria Land (Rees et al., 1989; Rowell & Rees, 1989) are part of this rifting event (Veevers et al., 1997). These latter rocks, which have been K-Ar dated at 586 ±20 Ma, also have characteristics typical of a within- plate rift setting (Rees et al., 1989; Rowell & Rees, 1989).

The formation of a passive margin in present-day eastern Australia, and possibly Antarctica, between 600 and 580 Ma, with final breakup at c. 560 Ma, has also been argued by Veevers et al.(1997). Whereas they argued that the separating entity was western Laurentia, Powell et al. (1994) used palaeomagnetic evidence to infer that rifting of Laurentia occurred prior to the "Sturtian" glacial event in South Australia. 259 Wingate (1998) further refined the age of the Laurentian separation to between 777 ± 7 Ma and 755 ± 3 Ma.

It is possible that both of these interpretations are partially correct. If the 777 to 755 Ma event calved off the major Laurentian block, the rifted margin related to that event must have been removed by the 600 to 580 Ma rifting, of which King Island is a remnant. The removal of the older rifted margin in this way explains the dismaying lack of voluminous mafic volcanics that should be expected from the first event, which is only supported by the 755 ± 3 Ma Mundine Well Dyke Swarm of far north Western Australia (Wingate, 1998), and the poorly dated Willouran Volcanic Province of South Australia (Crawford & Hilyard, 1989).

This scattered evidence stands in contrast to the growing body of data indicating a widespread rifting event at 600 to 580 Ma seen in New South Wales, South Australia, King Island, Tasmania and Antarctica. This is the subject of the next chapter. 260

Chapter 12: Late Neoproterozoic-Palaeozoic tectonic history of the southeastern Gondwana margin 12.0 Introduction 12.1 Comparison of NSW, SA, Vic and Tas sectors of the Gondwana margin 12.2 Evolution of the Gondwana margin 12.3 Implications for exploration 261

Chapter 12: Late Neoproterozoic-Palaeozoic tectonic history of the southeastern Gondwana margin

12.0 Introduction

As stated in Chapter 1, it was the intention of this study to place the Koonenberry Belt- Bancannia Trough within the continental framework demanded by its geophysical signatures (Figures 12.0.1; 12.0.2). Part 1 of this study dealt with the stratigraphy, structure and tectonics of the newly defined Koonenberry Fold-and-Thrust Belt, and was based solely on data derived from NSW. Part 2 has summarised possible correlative stratigraphy, structure and tectonics in eastern Australia. This chapter is intended to be a summary of the larger scale relationships implied by these correlations, as well as an examination of some questions implicit in these correlations.

12.1 Summary comparison of some sectors of the Gondwana margin

The updated tectonostratigraphy for all of the sectors of the Gondwana margin mentioned in this thesis is shown in Table 12.1.1. The chart should be used with caution, especially with respect to the Antarctic sectors; compared to other areas, mapping in the Antarctic is still at very basic reconnaissance level; many key exposures are subject of only a single visit and subsequent interpretation, and other relationships are not exposed due to ice cover. Nevertheless, the chart provides a basic dataset on which to base correlation schemes, while also highlighting areas in need of more work, as outlined below.

Key to the Table: Red: Rift volcanism Brown: Back-arc volcanism Dark green: Arc volcanism Dark Blue: Slope sedimentation Light Blue: Shelf sedimentation Magenta: Intracratonic sedimentation Light Green: Collisional processes Grey: Deformation without sedimentation Yellow: Deformation with orogenic volcanism

Figure 12.0.1 Figure 12.0.2

Eastern Australia Total Magnetic Eastern Australia Bouguer Gravity

Intensity modified from Morse et al., 1992 modified from Tarlowski et al.,1996 Koonenberry Belt indicated by box 262 Table reference list: 1 Sun, 1996 2 Powell et al., 1994 3 Thornton, 1974 4 Crawford et al., 1996a; Cayley & Taylor, 1996 5 Cayley & Taylor, 1998; Cayley & Taylor, 1997 6 Cayley & Taylor, 1997; Maher et al., 1997 7 Gray & Willman, 1991a; Cox et al., 1991 8 This study; Crawford & Berry, 1992; Adabi, 1997; Calver, 1998; Brown, 1986 9 Berry & Crawford, 1988 10 Berry, 1994; Turner et al., 1998 11 Banks, 1989a,b 12 Carey & Berry, 1988; Baillie, 1989b 13 Williams & Seymour, 1989 14 McClenaghan, 1989 15 Flottmann et al., 1993 16 Weaver et al., 1984 17 Tessensohn et al., 1981; Grew & Sandiford, 1982 18 Wodzicki et al., 1982; Stump et al., 1986 19 Kleinschmidt & Skinner, 1981; Gibson & Wright, 1985 20 Findlay, 1986; Tessensohn et al., 1981; Gibson et al., 1984; Stump et al., 1986 21 after Rowell et al., 1993; Findlay et al., 1984 22 Goodge, 1997; Rowell & Rees, 1989; Rees et al., 1989 23 after Rowell et al., 1992; Storey et al., 1992 24 Goodge, 1997 25 Rowell et al., 1988; Debrenne & Kruse, 1986; Rowell et al., 1992; Storey et al., 1996 26 Storey et al., 1996 27 Rowell et al., 1992; Burgess & Lammerink, 1979 28 Rowell et al., 1988; Rees et al., 1989; Storey et al., 1996 29 Rees et al., 1987 30 Skinner, 1965; Storey et al., 1996

12.2 Evolution of the southeastern Gondwana margin 12.2.1 Tectonostratigraphic history

Evolution of the Gondwana margin commenced between 700 and 600 Ma with the development of mixed carbonate-clastic rifted basins preserved in South Australia, 263 Tasmania, and Antarctica. These deposits may be the remnants of more extensive internal or marginal basins formed during the Rodinia breakup postulated by Powell et al. (1994), and Wingate (1998) which occurred between 777 ±7 Ma and 755 ± 3 Ma.

This early basin formation was followed by a widespread rifting event, whose evidence, in the form of large piles of transitional alkaline and tholeiitic volcanics, is found in all sectors except North Victoria Land (NVL). However, a long-wavelength, high-amplitude magnetic anomaly in NVL, was correlated by Finn et al. (1998) with the Dahlen Domain (Moore, 1996) of the Glenelg Zone in Victoria. This connection may also indicate evidence for rift-related volcanics under the NVL sector. It is postulated that this general rifting event led to the formation of a volcanic passive margin between 600 and 580 Ma (Direen & Crawford, 1998a; Berry & Crawford, 1992).

Evidence suggests that this margin remained passive for about 60 Ma in the northern sectors. However, Goodge (1997) argued that in the southern Transantarctic Mountains (TAM) ocean spreading quickly led to margin inversion sometime between 585 and 550 Ma. Deformation occurred as a result of tensional plate dynamics, rather than a compressional collision event. An active plate margin formed in the Australian sectors at around 525 Ma, when part of the passive margin began rifting away to form a marginal basin. Further outboard a proto-arc was established, while inboard, the Kanmantoo Trough sedimentation was initiated. These three events may be related to changes in lithospheric mantle dynamics under the developing orogenic zone as suggested by Foden et al. (1990).

Approximately 10 Ma elapsed before the onset of the major tectonothermal phase of the Ross-Delamerian Orogeny, although some authors (Haines & Flottmann, 1998a) have recently proposed an onset of deformation around 523 Ma. This earlier date, discussed in chapter 9, leaves a "breathing space" between rifting and orogenesis of just 2 Ma, which is not statistically distinguishable with the dating techniques used. In either case, the transition from tensional to compressional tectonics was relatively rapid.

The tectonostratigraphic datasets outlined above strongly suggest that the Ross- Delamerian Orogen developed into two distinct zones. The internal zone, consisting of the Adelaide Fold Belt, Wilson Terrane, and perhaps the Skelton and Koettlitz Groups of the southern Transantarctic Mountains, was deformed earlier than the external zone, made up of the Koonenberry Belt, Glenelg Zone, Bowers Terrane and the remainder of the Transantarctic Mountains. 264

The internal zone developed into a thick-skinned tectonothermal fold-and-thrust orogen, containing syn- and post-tectonic granitoids, Buchan-type metamorphism, and basement involvement of the older epicontinental basin sequences (e.g. Jenkins, 1990; Flottmann et al., 1993a). Strike-slip or oblique components of deformation were reported from the southern TAM (Pensacola Mtns) by Storey et al. (1996) and Goodge (1997). Timing of deformation ranges from Early Cambrian (516 Ma) in South Australia through to the Early Ordovician (Arenig) in NVL and the TAM, a period spanning some 30 Ma.

In contrast, the external zone experienced thermally mild, generally thin-skinned deformation. This appears to be dynamically linked to the collision and obduction of a west-facing boninitic fore-arc with the thinned continental margin (Berry & Crawford, 1988). The age of this colliding arc is constrained to be between 516 and 504 Ma, based on dates from tonalites in Tasmania (Turner et al., 1998). Prior to the collision, this arc had subducted much of the marginal basin formed from 525 Ma onward. The date of the collision and inversion varies across the sectors, and also within sectors (this study), but is generally constrained to be between the Ordian and the Arenig. Collision was rapidly followed by syn- to post-collisional marginal marine sedimentation and calc-alkaline volcanism, dated between 505 and 490 Ma (Perkins, 1994; Crawford et al., 1996b; this study). The later timing, shorter duration and ongoing sedimentation during orogenesis are distinctive features of the external zone.

On the Australian mainland, the external zone shows thin-skinned character, with west- and southwest-directed thrusting. Tasmania, on the other hand, displays a complex pattern of thrust sheets and foreland-like sedimentation in a rapidly changing stress field (after Berry, 1994; and SeIley, 1997). Involvement of possible crystalline basement rocks in some parts of the Tasmanian sector has also recently been demonstrated (Drummond et al., 1996). The differences between the Australian mainland and Tasmanian signatures of the Delamerian Orogeny has not yet been satisfactorily explained; Berry (1994) outlined some similarities in fold style between western Tasmania and the Olary block of the Curnamona Craton.

True post-Delamerian sedimentary sequences vary along the margin, from intracratonic in the Warburton Basin and sedimentation hiatuses in the Koonenberry and Mt Lofty Ranges, through to marginal marine sequences in western Victoria and Tasmania, and deep marine sedimentation in NVL. Other deep marine sequences may yet be discovered in the TAM areas. In the northern sectors, apparent cratonic 265 character is thought to be the result of an eastward subduction jump during Ordovician time (chapter 8).

This phase of sedimentation was terminated by the first major deformation in the formation of the Lachlan Fold Belt, the Benambran event. The major characteristics of this Late Ordovician-Early Silurian event are its thin-skinned character and complete lack of orogenic magmatism. It produced a coaxial deformation to the earlier Delamerian fabrics in the Koonenberry Belt, and its effects were also felt as far inboard as the Warburton Basin, producing a northwest-vergent fold-and-thrust belt there. In western Victoria , this event produced strong west-directed folding and thrusting (e.g Moyston Fault, Cayley & Taylor, 1997). Despite the widespread nature and strong deformation experienced by the latter regions during this event (see also Gray & Foster, 1997b), it has yet to be recognised in the Adelaide Fold Belt, Tasmania, NVL or the TAM; overprinting deformations in syn-to-post Delamerian sediments of the TAM reported by Rees et al. (1987) may be Silurian or Devonian in age.

The Benambran event in NSW was followed by the development of a series of intermontane basins (Neei & BottriII, 1991), whereas the Warburton Basin entered a depositional hiatus. In Victoria, the locus of subduction is believed to have shifted to the east, although the position and number of subduction zones involved is contentious (Soesoo et al., 1997; O'Halloran & Bryan, in press). Tasmania records a return to assumed open marine shelf conditions, but elsewhere data is sparse for this time period.

The next major event recorded in the evolved margin complexes is diachronous felsic magmatism (Early to Late Devonian) and east-vergent thrusting in Victoria and NVL; west-directed thrusting with complex overprinting of early structures occurred in Tasmania (Williams & Seymour, 1989; Selley, 1997). Termination of this event, termed the Tabberabberan in Australia and the Borchgrevink in Antarctica, led to the cratonisation of the now-multiply modified margin. Middle and Late Devonian intracratonic basins are found in NSW, eastern SA, NVL and the TAM. These basins record high-crustal level deformation related to a composite Carboniferous event. Two events have been ascribed to the Carboniferous in the literature: one is the amalgamation of the terranes of the New England Fold Belt with the Lachlan Orogen (Coney et al., 1990; Scheibner, 1996b); the other is the Alice Springs Orogeny, which developed south-vergent folds and thrusts accompanied by granitoid magmatism in Central Australia. The Alice Springs Orogeny is thought to be related to mid- Carboniferous north-south convergence of Australia and Laurasia (Klootwijk, 1995). 266

Granites possibly associated with this event are found in the Warburton Basin and, oddly, Tasmania (McClenaghan, 1989).

The tectonostratigraphic history of these Gondwana margin sectors is thus a complex temporal mosaic of magmatism, sedimentation and deformation. It is, however, unified by two common themes: rifting between c.700 and 600 Ma; and after 525 Ma, successive accretion of oceanic elements and/or terranes against the craton (cf. Crook, 1980b; Gray & Foster, 1997b). This pattern of events has produced relatively continuous fold belts, traceable for thousands of kilometres, which step out from the original rift margin in both space and time.

The following section deals with some related questions about these foldbelts.

12.2.2 Delimiting an Orogen or "What is an orogen, anyway?"

In discussing the various schemes outlined above, a problem arises in the use of the term "Orogen" or "fold belt" to describe various edifices, and what they mean tectonically. Throughout this study I have used the term "fold belt" to describe a geographically distinct area of folded rocks; the folds may be of single or multiple ages. No genetic tectonic connotation is implied, although I have modified the term in some cases to "fold-and-thrust-belt" where both of these features are demonstrated.

I have used the term "Orogen" to refer to a collection of separate fold belts which have formed as the result of some set of events over some defined time frame. Again, no definite tectonic scenario (e.g. collision) is implied. Thus I have described the Ross- Delamerian Orogen, which formed over ?Middle Cambrian to Early Ordovician time, and is composed of distinct fold belts in NSW, SA, Victoria, NVL and the TAM. I have also used the term Lachlan Orogen (Gray & Foster, 1997b), which comprises fold belts in central NSW; western, central and eastern Victoria; eastern Tasmania; and the Robertson Bay Terrane in Antarctica. The Lachlan Orogen appears to have experienced several events during its development: these are variously termed the Benambran, Bowning, Bindian and Tabberabberan events (Gray & Foster, 1997b). Previously these were thought to represent separate orogenies, but recent structural and metamorphic analysis has shown this view to be inaccurate (Gray & Foster, 1997b), and the analysis presented above does not use the "separate orogenies" paradigm. As interpreted, the various "events" reflect the ongoing development of the Orogen in an interpreted plate tectonic regime. 267 A problem arises when considering that one fold belt, such as the Koonenberry FTB, can belong to both the Ross-Delamerian and the Lachlan Orogens using the definitions outlined above. Thus anyone seeking to delimit either orogen explicitly on a map would be forced into drawing a zone of overlap, as a line is clearly inappropriate. This argument has already been expressed by Mills (1992), and indeed the "zone of overlap" approach was used by Zhou & Mills (1990) and Zhou (1993).

An alternative viewpoint considers that only elements added to the developing margin, either by accretion, intrusion or deposition, within defined time limits, constitute the fabric of an orogen. In this case, parts of the Lachlan Orogen can be considered to have been emplaced over the older Delamerian Orogen in the Benambran event (Cayley & Taylor, 1998). This is not quite as simple as it sounds, and leads to as many problems in delimiting the orogens as the previous viewpoint. For example, in western Victoria the boundary between the Delamerian and Lachlan Orogens is considered to be the Moyston Fault, a major west-vergent thrust. This is easily represented as a single line in map view. But the potential exists for this thrust to tip out; or to splay; or detach footwall- or hanging-wall horses. This latter permutation is probably the case at the eastern edge of the Kalkee Domain (see Chapter 10). Also the footwall of the thrust (the Delamerian Orogen) continues beneath the hanging-wall (Lachlan Orogen), perhaps for many hundreds of kilometres; backthrusts from the decollement level can bring up portions of the footwall. Using this concept, the Heathcote, Mt Wellington and Jamieson greenstone belts in Victoria (Crawford & Keays, 1987; Crawford & Cameron, 1985) represent tectonic inliers of the Delamerian Orogen within the Lachlan Orogen, having originally been accreted in the Late Cambrian. In far western NSW, this definition leads to the Koonenberry fold belt being considered part of the Delamerian which has undergone later deformation related to the formation of the Lachlan Orogen. However, the whereabouts of the Lachlan Orogen responsible for the deformation, is indeterminate. Using this definition, the boundary must occur east of the Koonenberry Fault and somewhere west of Cobar, under the cover of the Murray Basin. Such a scheme seems generally unsatisfactory, and in any case still cannot be represented accurately on a map.

In summary, currently acceptable methods of defining an orogen both lead to difficulties or in some cases, absurdities, when trying to delimit the orogen on maps. These difficulties arise as much from the oversimplification of a complex four- dimensional system (three space dimensions and time, all vectors) into a two- dimensional space such as a geological map or cross-sections (two vector dimensions with scalar time), as from any problems with the definitions being used. It is physically 268 impossible to simplify the dimensions of any system and not lose information; unfortunately for those seeking to use maps to define orogenic boundaries, the information lost is precision, which is the whole point of mapping. It is thus suggested that the drawing of orogenic boundaries be accompanied by appropriate caveats, or cease altogether.

12.2.3 Ross-Delamerian orogenic dynamics or "How and why did it become an orogen ?"

As discussed in Chapter 9, the Ross-Delamerian Orogen has been thought to represent a collisional orogenic system (Gibson, 1987; Flottmann et al., 1994). However, the history outlined above is difficult to reconcile with such a general model, for the following reasons: • the strong contrast in deformation style between internal and external zones (this study); • the restriction of colliding sequences to the external zone (this study); • an earlier onset of deformation in the internal zone compared to the external zone, including (in some cases) deformation before the genesis of the colliding arc (this study); • passive obduction mechanism in the external zone (Berry & Crawford, 1988); • trailing syn-collisional sedimentary geometry (this study); • lack of an everywhere-recognisable foreland-basin sequence in the internal zone (Coney et al., 1990).

For these reasons, it is my conclusion that the fundamental cause of the Ross- Delamerian Orogeny is not a collisional event, but a function of lithospheric mantle dynamics, as proposed by Grew & Sandiford (1982), Foden et al. (1990) and Jenkins & Sandiford (1992). This model has the advantage of being able to explain thermal anomalies and uplift of basement rocks in the cratonic areas, including the Wilson terrane and East Antarctic Shield (Grew & Sandiford, 1982). The corollary of this model is that most of the tectonics and plate kinematics of the continental accretionary margin are actually secondary responses to much larger forces acting under the craton. This may also be the case with the complex Carboniferous event(s).

A further question of interest arises when comparing the two deformation events in the Lachlan Orogen (including later Koonenberry-Warburton sequences). Why is the Silurian event devoid of orogenic magmatism, when the Devonian is rife with it? Could this also be the expression of mantle dynamics coming into play in the latter event? 269

Both "problems" suggest different orogenic outcomes even though the plate regime remained relatively constant through time. It is proposed that events experienced along the entire developing margin, such as the initial phases of rifting and later pulses of orogenic magmatism, are mantle-driven, whereas processes occurring more locally are the product of changes or interactions in plate-geometry in discrete sectors.

12.2.4 Summary

Both of the issues outlined above to some extent derive from the way in which fold- belts and orogens are increasingly seen in genetic terms. This in turn is caused by the strength of the plate-tectonic paradigm in relating sequences of rocks and patterns of deformation, to analogue plate settings. This approach needs to be used with caution. The genetic model derived from the evidence above, that of a sequence of orogens and their component fold-belts stepping out from the craton over time is based on several different collisional analogues in the north-east and south-west Pacific, as well as extensional analogues in the Atlantic and Indian Oceans.

I believe the definition of orogen and fold-belts chosen in this study more closely represents the evolving nature of a complex system, with less tendency for any discrete element included within a fold-belt to be identified as the causal factor of orogenesis. For example, using these definitions it is incorrect to say that the collision of the New England Orogen with the Lachlan Orogen produced a new deformation fabric in both the Lachlan and the Delamerian Orogens. Rather, the accretion of terranes and other oceanic elements at the outboard plate margin over a definite timeframe within the evolving New England Orogen led to structural readjustments of internal fold belts which represent earlier, abandoned plate margin settings. The difference is subtle, but important for the understanding of orogenesis.

In compiling the evidence above, I have endeavoured to examine all the sequences described myself, rather than solely rely on the interpretations of others. This was not possible for the Antarctic sectors, which I thus consider the weakest in the model. Also necessary to these interpretations was considering information from as many locations as demanded by the setting: geophysics shows that the Koonenberry Belt is related in some way to other parts of Australia; geophysics also shows that those other parts were once in proximity to Antarctica. Therefore all these regions have been considered: an inductive model with only limited conclusions that satisfies the newest 270

data from a wide variety of sources, is inherently preferable to one with many conclusions based on relatively fewer, limited data.

12.3 Implications for exploration: Koonenberry Belt

As outlined in Chapter 8, understanding of the tectonostratigraphic history of a fold-belt can lead to significant appreciation of its resource potential. Whereas even an overview of the resource potential of the entire margin sector is well beyond the scope of this study, some important facts arise from the analysis above.

With regard to the Koonenberry Belt, the original focus of this study, some important correlations exist. The external zone of the Delamerian Orogen, of which the Koonenberry forms a part, also contains western Victoria and western Tasmania. Both regions are significantly mineralised. Western Victoria hosts minor VHMS mineralisation and major turbidite-hosted Au (Crawford et al., 1996a). Western Tasmania hosts a wide variety of mineral deposits including Sn skams, porphyry Cu- Au, polymetallic base metal and Au rich VHMS, "Irish style" carbonate-hosted Pb-Zn- Ag, and structurally-controlled Devonian vein Pb-Zn-Ag.

The correlation of these regions with the Koonenberry Belt enhances some of the peedictions made in Chapter 8. Including the other styles of mineralisation mentioned, and the generally underexplored nature of all three regions, this composite belt has significant potential for major mineral discoveries to be made. 271

Chapter 13: General Conclusions

Chapter 13: General Conclusions and Synthesis

The Koonenberry-Bancannia region of far western New South Wales, formerly known as the Wonominta Block, is a complex, polydeformed fold belt of Palaeozoic age, situated in a system of major geophysical lineaments. Geological investigations have revealed that this fold belt contains deformed rocks of Late Neoproterozoic to Carboniferous age.

Three of these sequences, the Early-Middle Cambrian Teltawongee and Gnalta Groups, and the Cambro-Ordovician Ponto Complex, were investigated in detail. The Teltawongee Group is a thick and laterally extensive pile of turbidites, probably formed on a continental slope, and is a possible lateral facies equivalent of tectonically disrupted Gnalta Group shelf sequences. The Ponto Complex is a series of multiply deformed allochthonous slices occurring between two regional faults, and appears to have been diachronously emplaced over the Teltawongee and Gnalta Groups in the Late Cambrian.

Detailed investigation of igneous units cropping out throughout the Koonenberry region reveals three tholeiitic and two calc-alkaline suites, and an alkaline suite. Tholeiitic suites are dated at 587 Ma and two at around 500 Ma, and appear to be related to episodes of extension during rifting of various types. One of the calc-alkaline suites, dated at 525 Ma also appears to be rift-related, whereas the other, dated around 500 Ma is probably related to post-collisional volcanism. The alkaline suite is of Permian age (264Ma), and has a within-plate signature and is associated with diamond mineralisation.

Mapping and structural investigations throughout the region suggest there is extensive repetition of stratigraphy and many listric reverse faults. These findings are confirmed by detailed quantitative and qualitative analysis of potential field data constrained by a comprehensive petrophysical dataset. In addition, forward modelling of geophysical data indicates strong crustal layering and decollements; involvement of older Neoproterozoic crust; east- and west-vergence of thrusts and reverse faults; and large volumes of magnetic volcanics, occurring as coherent piles and structural slices throughout the belt. 272 Structural analysis indicates that the region has been subjected to two episodes of thrust deformation and metamorphism, one Late Cambrian, and one Middle Ordovician to Middle Silurian. These were followed by episodes of high crustal level deformation in the Devonian and Carboniferous. The major Koonenberry Fault has been interpreted as a Cambrian backthrust which was oroclinally bent in the Carboniferous into the trend of the Darling River Lineament; this Lineament only shows evidence for Palaeozoic deformations. The associations between geophysical lineaments and Palaeozoic deformation features, as well as the extension of these structures onto the craton, suggests that a "Tasman Line" based on geophysical evidence should be abandoned as misleading.

Interpretation of the Koonenberry-Bancannia region as a polydeformed, thin-skinned fold-and-thrust belt has solved many previous anomalies associated with vertical, thick- skinned interpretations. These include a lack of significant metamorphic grade changes throughout the belt, and the multiple-deformations in the Ponto Complex.

Comparison of the Koonenberry Fold and Thrust Belt (FTB) to the Adelaide Fold Belt of South Australia shows fewer similarities than previously thought. Instead, the Koonenberry FTB can be shown to have strong affinities in age and tectonic style, including some equivalence in sedimentary and volcanic packages, with external zones of the Ross-Delamerian Orogen. These zones include the Warburton Basin and Glenelg Zone of western Victoria on mainland Australia; King Island and western Tasmania; and the Bowers Terrane of North Victoria Land and portions of the Transantarctic Mountains in Antarctica.

These similarities suggest that the Koonenberry region formed part of a continuous continental margin along the southeastern side of the Gondwana Supercontinent between the Late Neoproterozoic after Rodinian breakup, until the Carboniferous, prior to Pangaea assembly. This margin developed in two stages of rifting, and experienced serial accretion and deformation from Early Cambrian times onward. The length of such a margin implies temporal and spatial complexities in the tectonic development, although some events appear to have been experienced along the entire edifice. These events are believed to have been controlled by large-scale mantle processes, with more localised events related to the influences of interacting plate geometries.

In the context of the evolving plate margin, the Koonenberry Fold-and-Thrust Belt is considered to form a part of both the Ross-Delamerian and Lachlan Orogens. However, an alternative viewpoint considers that it forms part of the Delamerian 273 Orogen only; this leads to some unsatisfactory consequences, and has not been adopted.

The nature of the tectonic development of the Koonenberry FTB, and its correlation with other geological provinces in southeastern Australia, has implications for its metallogenic and non-metallic resource budgets. In particular, the belt can be expected to have significant prospectivity for various styles of base metal and gold mineralisation, in addition to diamonds. Hydrocarbon exploration will remain a high risk activity, due to few validated plays and structural complexities 274

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Appendix 1 Fully reduced Bouguer gravity values

Stations are manually terrain corrected using Hammer's graticule method to zone M Tcorrection (TC) is in mGal; Coordinates are AMG zone 54; Gobs and Free Air in Gal Bouguer Anomaly (BA) in mGal Nundora-Wonnaminta Station # mE mN inn! G obs Free Air TC BA/Line 9621.0001 585916 603137 121 979.329600 979.379191 0.00 -25.78Nundora 9621.0002 586822 602818 120 979.329660 979.379414 0.00 -26.14Nundora 9621.0003 587508 603143 121 979.329320 979.379178 0.00 -26.05Nundora 9621.0004 587700 603147 121 979.329200 979.379174 0.00 -26.16Nundora 9621.0005 588657 603556 122 979.328730 979.378875 0.01 -26.13Nundora 9621.0006 589645 603620 122 979.329310 979.378824 0.00 -25.51Nundora 9621.0007 590559 603428 125 979.331850 979.378956 0.00 -22.51N u ndora 9621.0008 591484 603148 126 979.337380 979.379150 0.01 -16.97N undo ra 9621.0009 592418 603358 127 979.341500 979.378994 0.00 -12.50Nundora 9621.0010 592779 603175 126 979.342190 979.379123 0.00 -12.14N undora 9621.0011 593694 603023 129 979.342980 979.379226 0.00 -10.86Nundora 9621.0012 594113 602506 128 979.343860 979.379593 0.00 -10.55Nundora 9621.0013 595050 602214 129 979.345870 979.379797 0.00 -8.54Nundora 9621.0014 595620 601801 130 979.346790 979.380088 0.00 -7.72Nundora 9621.0015 595807 601811 131 979.347230 979.380080 0.00 -7.07Nundora 9621.0016 596557 600943 131 979.348920 979.380696 0.00 -6.00N undora 9621.0017 597242 600711 134 979.350910 979.380858 0.00 -3.58Nundora 9621.0018 597518 600591 124 979.351830 979.380942 0.01 -4.71N undora 9621.0019 598427 600651 132 979.357180 979.380893 0.00 2.26Nundora 9621.0020 598652 600685 141 979.356910 979.380868 0.00 3.79Nundora 9621.0021 599557 601233 153 979.359060 979.380469 0.00 8.70Nundora 9621.0022 599958 601655 146 979.359770 979.380165 0.00 8.33Nundora 9621.0023 600122 601996 147 979.359730 979.379920 0.00 8.74Nundora 9621.0024 600333 602963 156 979.359000 979.379226 0.00 10.47Nundora 9621.0025 600582 603494 153 979.360060 979.378845 0.00 11.32Nundora 9621.0026 600697 603916 155 979.359270 979.378542 0.00 11.23Nundora 9621.0027 601094 604176 169 979.359460 979.378353 0.00 14.36Nundora 9621.0028 601449 604437 169 979.359800 979.378164 0.00 14.89Nundora 9621.0029 602178 605062 166 979.359970 979.377712 0.01 14.93Nundora 9621.0030 602946 605563 176 979.358770 979.377349 0.00 16.05Nundora 9621.0031 603459 605528 168 979.359410 979.377370 0.00 15.10Nundora 9621.0032 603825 605877 171 979.358350 979.377118 0.00 14.88Nundora 9621.0033 604621 606490 170 979.356510 979.376674 0.00 13.29Nundora 9621.0034 605461 606316 171 979.357630 979.376793 0.00 14.49Nundora 9621.0035 605783.4 606062.5 167 979.358860 979.376972 0.00 14.75Nundora 9621.0036 606277 605657 184 979.360830 979.377258 0.00 19.78Nundora 9621.0037 607017.8 605220.5 177 979.364340 979.377565 0.00 21.60Nundora 9621.0038 607735.3 605712 180 979.363540 979.377209 0.01 21.76Nundora 9621.0039 608464 606243 183 979.360260 979.376824 0.00 19.45Nundora 9621.0040 609406 606601 189 979.357480 979.376561 0.00 18.11Nundora 9621.0041 610275 607096 180 979.355680 979.376201 0.00 14.90Nundora 9621.0042 611171 607353 191 979.353570 979.376010 0.00 15.14Nundora 9621.0043 611976 607491 194 979.354550 979.375906 0.00 16.82Nundora 9621.0044 612511 607329 187 979.355750 979.376018 0.01 16.54Nundora 9621.0045 613090 607017 179 979.354280 979.376236 0.00 13.27Nundora 9621.0046 614047 606953 186 979.352320 979.376275 0.02 12.66Nundora 9621.0047 615016 606810 187 979.352440 979.376370 0.01 12.88Nundora 9621.0048 616027 606904 181 979.353180 979.376295 0.01 12.51N undora 9621.0049 616140 606859 180 979.353390 979.376326 0.00 12.48Nundora 9621.0050 617110 607017 174 979.354800 979.376206 0.00 12.83Nundora 9621.0051 618296 606897 168 979.355710 979.376282 0.00 12.49Nundora 9621.0052 619113 607424 180 979.354400 979.375899 0.02 13.94Nundora 9621.0053 620042 607417 172 979.355290 979.375897 0.00 13.24Nundora 9621.0054 620928 607811 168 979.351840 979.375608 0.00 9.29Nundora 9621.0055 621942 607820 182 979.352720 979.375593 0.00 12.94Nundora 9621.0056 622856 608202 186 979.351610 979.375313 0.01 12.91N undora 9621.0057 623642 608710 181 979.351740 979.374943 0.00 12.41Nundora 9621.0058 624465 609368 184 979.350050 979.374466 0.00 11.79Nundora

Page 1 of 5 Appendix 1

Station # mE mN masi G obs Free Air TC BA/Line 9621.0059 625222 609725 190 979.347310 979.374205 0.00 10.49N undora 9621.0060 625440 609666 191 979.346900 979.374245 0.00 10.24N undora 9621.0061 626416 609635 180 979.348860 979.374259 0.00 10.02N undora 9621.0062 626674 609778 176 979.348850 979.374155 0.00 9.33Nundora 9621.0063 627435 609777 176 979.349080 979.374149 0.00 9.56N undora 9621.0064 628245 609986 188 979.346320 979.373993 0.00 9.32Nundora 9621.0065 629217 610222 198 979.342720 979.373816 0.00 7.87N undora 9621.0066 630128 610522 204 979.341600 979.373594 0.00 8.15N undora 9621.0067 630660 609706 197 979.344470 979.374172 0.00 9.06N undora 9621.0068 631419 609400 204 979.343490 979.374384 0.01 9.26N undora 9621.0069 631664 609395 204 979.342700 979.374386 0.05 8.50Nundora 9621.0070 632504 609820 208 979.340660 979.374075 0.00 7.51Nundora 9621.0071 633309 610336 206 979.339650 979.373699 0.00 6.49Nundora 9621.0072 633716 610434 205 979.337210 979.373625 0.03 3.95N undora 9621.0073 634227 610403 202 979.339700 979.373643 0.02 5.82Nundora 9621.0074 634922 610913 183 979.342040 979.373272 0.00 4.78N undora 9621.0075 635413 611806 176 979.341310 979.372630 0.00 3.31N undora 9621.0076 635959 612616 169 979.341040 979.372047 0.00 2.25Nundora 9621.0077 636794 613006 169 979.340110 979.371761 0.00 1.60N undora 9621.0078 637672 613036 175 979.338310 979.371731 0.00 1.01Nundora 9621.0079 638702 613053 177 979.338240 979.371710 0.00 1.36Nundora 9621.0080 639668 613417 174 979.337560 979.371441 0.00 .36Nundora 9621.0081 640426 614023 164 979.338730 979.371001 0.00 .00Nundora 9621.0082 641045 614270 159 979.339660 979.370819 0.00 .13Nundora 9621.0083 595228 602051 130 979.345860 979.379912 0.00 -8.47Nundora 9621.0084 606832.8 605171.5 178 979.363580 979.377602 0.00 21.00Nundora 9621.0085 606924.6 605196.5 175 979.364950 979.377583 0.02 21.82Nundora 9621.0086 607122.8 605269 173 979.365500 979.377530 0.01 22.02Nundora 9621.0087 607218.1 605324 174 979.365280 979.377490 0.00 22.03Nundora 9621.0088 607315.2 605372 176 979.364920 979.377455 0.00 22.10Nundora 9621.0089 607406.2 605428.5 176 979.365240 979.377414 0.00 22.46Nundora 9621.0090 607474.9 605487.5 176 979.364850 979.377371 0.00 22.11Nundora 9621.0091 607558.2 605553 178 979.365010 979.377324 0.00 22.71Nundora 9621.0092 607634.2 605624.5 159 979.364250 979.377272 0.00 18.26Nundora 9621.0093 607815.8 605785.5 179 979.362580 979.377156 0.00 20.65Nundora 9621.0094 613384 607014 183 979.354040 979.376236 0.03 13.84N undora

Marrapina-Nuntherungie Station # mE mN masi G obs Free Air TC BA/Line 9621.0100 608395 561830 152 979.356270 979.408701 0.00 -22.52Marrapina 9621.0101 609340 562042 156 979.313340 979.408541 0.00 -64.51Marrapina 9621.0102 610281 562265 162 979.313160 979.408374 0.00 -63.34Marrapina 9621.0103 611153 562704 162 979.313120 979.408051 0.00 -63.05Marrapina 9621.0104 612000 563311 165 979.315950 979.407607 0.00 -59.19Marrapina 9621.0105 612798 563820 167 979.319250 979.407234 0.00 -55.12Marrapina 9621.0106 613575 564484 169 979.365880 979.406750 0.02 -7.60Marrapina 9621.0107 614357 565016 170 979.434640 979.406361 0.00 61.73Marrapina 9621.0108 615298 565245 171 979.437660 979.406189 0.00 65.12Marrapina 9621.0109 616260 565593 172 979.440100 979.405931 0.00 68.01Marrapina 9621.0110 617147 565995 173 979.441530 979.405634 0.00 69.94Marrapina 9621.0111 618074 566366 172 979.444640 979.405360 0.00 73.12Marrapina 9621.0112 618998 566748 168 979.447940 979.405078 0.00 75.92Marrapina 9621.0113 619917 567150 166 979.450530 979.404781 0.00 78.41 Marrapina 9621.0114 620869 567456 165 979.452480 979.404553 0.00 80.39Marrapina 9621.0115 621864 567618 164 979.387270 979.404428 0.00 15.11Marrapina 9621.0116 622735 568000 164 979.454630 979.404146 0.00 82.75Marrapina 9621.0117 623640 568411 173 979.454160 979.403843 0.01 84.37Marrapina 9621.0118 624622 568748 175 979.454150 979.403592 0.02 85.01Marrapina 9621.0119 625568 569083 177 979.453730 979.403343 0.00 85.22Marrapina 9621.0120 626477 569687 170 979.455850 979.402900 0.00 86.40Marrapina 9621.0121 626802 570511 169 979.454970 979.402305 0.00 85.92Marrapina 9621.0122 627039 571080 175 979.452450 979.401894 0.00 84.99Marrapina 9621.0123 627200 571536 176 979.451740 979.401564 0.04 84.85Marrapina 9621.0124 627777 572385 175 979.451570 979.400949 0.00 85.06Marrapina

Page 2 of 5 Appendix 1

Station # mE mN masl G obs Free Air IC BA/Line 9621.0125 628474 573030 179 979.431480 979.400479 0.00 66.22Marrapina 9621.0126 629069 573884 175 979.365240 979.399860 0.00 -.18Marrapina 9621.0127 629521 574725 176 979.367360 979.399251 0.00 2.74Marrapina 9621.0128 629971 575491 174 979.368900 979.398697 0.00 4.44Marrapina 9621.0129 630654 575910 175 979.370180 979.398390 0.00 6.23Marrapina 9621.0130 631095 576936 180 979.373720 979.397649 0.00 11.49Marrapina 9621.0131 631851 577652 185 979.376660 979.397127 0.00 15.94Maffapina 9621.0132 632283 578565 179 979.376930 979.396468 0.00 15.68Marrapina 9621.0133 632936 579239 183 979.378880 979.395978 0.00 18.91Marrapina 9621.0134 633192 579417 183 979.379160 979.395848 0.00 19.32Marrapina 9621.0135 633822 579686 183 979.378850 979.395649 0.00 19.21Marrapina 9621.0136 634617 580386 185 979.379610 979.395139 0.00 20.87Marrapina 9621.0137 635336 581025 190 979.380600 979.394674 0.00 23.31Marrapina 9621.0138 635643 581942 189 979.380340 979.394012 0.00 23.52Marrapina 9621.0139 635880 582903 187 979.381280 979.393320 0.00 24.76Marrapina 9621.0140 636425 583693 185 979.382530 979.392749 0.00 26.18Marrapina 9621.0141 636935 584542 187 979.430480 979.392135 0.00 75.14Marrapina 9621.0142 637476 585385 188 979.428630 979.391525 0.00 74.10Marrapina 9621.0143 637782 586267 187 979.428200 979.390889 0.00 74.11Marrapina 9621.0144 638449 586981 187 979.427000 979.390371 0.00 73.43Marrapina 9621.0145 639141 587735 194 979.425450 979.389824 0.00 73.80Marrapina 9621.0146 640021 588215 198 979.422940 979.389471 0.00 72.43Marrapina 9621.0147 640877 588602 194 979.423440 979.389186 0.00 72.43Marrapina 9621.0148 641416 589425 197 979.421890 979.388590 0.00 72.06Marrapina 9621.0149 642256 589267 206 979.419700 979.388696 0.00 71.54Marrapina 9621.0150 642990 590003 220 979.348670 979.388161 0.00 3.80Marrapina 9621.0151 643662 589552 218 979.415810 979.388478 0.00 70.23Marrapina 9621.0152 644636 589751 218 979.415410 979.388326 0.00 69.98Marrapina 9621.0153 645593 590007 222 979.414040 979.388133 0.00 69.59Marrapina 9621.0154 646348 589456 222 979.414750 979.388521 0.00 69.91Marrapina 9621.0155 647371 589292 224 979.414120 979.388628 0.00 69.57Marrapina 9621.0156 648370 589395 217 979.416610 979.388544 0.01 70.78Marrapina 9621.0157 649359 589545 215 979.415280 979.388427 0.01 69.17Marrapina 9621.0158 650322 589537 215 979.414640 979.388423 0.01 68.53Marrapina 9621.0159 651289 589281 219 979.413280 979.388597 0.09 67.87Marrapina 9621.0160 652308 588991 221 979.346010 979.388794 0.01 .71Marrapina 9621.0161 653275 588737 222 979.412890 979.388966 0.01 67.62Marrapina 9621.0162 654119 589367 232 979.410270 979.388506 0.00 67.42Marrapina 9621.0163 654851 589922 235 979.408420 979.388101 0.00 66.56Marrapina 9621.0164 655597 590428 248 979.404340 979.387730 0.00 65.41Marrapina 9621.0165 656482 591049 247 979.402230 979.387276 0.03 63.59Marrapina 9621.0166 657343 591608 243 979.401980 979.386866 0.00 62.93Marrapina 9621.0167 657967 592322 237 979.402040 979.386348 0.00 62.33Marrapina 9621.0168 658652 593027 232 979.402370 979.385836 0.00 62.19Marrapina 9621.0169 659287 593805 222 979.404320 979.385272 0.00 62.73Marrapina 9621.0170 659692 594243 221 979.337960 979.384954 0.00 -3.51Marrapina

Macs Tank Station # mE mN masi G obs Free Air TC BA/Line 9621.5100 631300 556200 221 979.386740 979.412572 0.00 17.66Macs_Tank 9621.5101 631400 556216 219 979.387690 979.412559 0.16 18.38Macs_Tank 9621.5102 631500 556233 220 979.387690 979.412546 0.16 18.59Macs_Tank 9621.5103 631600 556249 219 979.388200 979.412533 0.16 18.92Macs_Tank 9621.5104 631700 556265 216 979.389120 979.412521 0.16 19.26Macs_Tank 9621.5105 631800 556281 215 979.390040 979.412509 0.17 20.01Macs_Tank 9621.5106 631900 556298 215 979.389910 979.412495 0.16 19.88Macs Tank 9621.5107 632000 556314 216 979.389810 979.412483 0.16 19.99Macs_Tank 9621.5108 632100 556330 217 979.389590 979.412471 0.16 19.98Macs_Tank 9621.5109 632200 556346 219 979.389320 979.412458 0.16 20.12Macs_Tank 9621.5110 632300 556363 221 979.389080 979.412445 0.16 20.28Macs_Tank 9621.5111 632400 556379 222 979.388820 979.412433 0.16 20.23Macs Tank 9621.5112 632500 556395 224 979.388940 979.412420 0.16 20.76Macs_Tank 9621.5113 632600 556411 223 979.389290 979.412408 0.16 20.92Macs_Tank 9621.5114 632700 556428 224 979.388880 979.412395 0.16 20.72Macs_Tank

Page 3 of 5 Appendix 1

Station # mE mN masi G obs Free Air TC BA/Line 9621.5115 632800 556444 225 979.389280 979.412382 0.16 21.33Macs_Tank 9621.5116 632900 556460 226 979.389200 979.412370 0.16 21.46Macs_Tank 9621.5117 633000 556476 228 979.389040 979.412357 0.16 21.71 Macs_Tank 9621.5118 633100 556493 230 979.388880 979.412344 0.17 21.96Macs_Tank 9621.5119 633200 556509 239 979.387380 979.412332 0.17 22.25Macs_Tank 9621.5120 633300 556525 235 979.387620 979.412319 0.16 21.70Macs_Tank 9621.5121 633400 556541 235 979.387960 979.412307 0.16 22.06Macs_Tank 9621.5122 633500 556558 236 979.387670 979.412294 0.16 21.98Macs_Tank 9621.5123 633600 556574 240 979.387100 979.412281 0.16 22.20Macs_Tank 9621.5124 633700 556590 241 979.386830 979.412269 0.16 22.14Macs_Tank 9621.5125 633800 556606 241 979.386900 979.412256 0.16 22.23Macs_Tank 9621.5126 633900 556623 241 979.386990 979.412243 0.16 22.33Macs_Tank 9621.5127 634000 556639 239 979.387530 979.412231 0.16 22.49Macs_Tank 9621.5128 634100 556655 238 979.387910 979.412218 0.16 22.68Macs_Tank 9621.5129 634200 556671 238 979.387780 979.412206 0.16 22.57Macs_Tank 9621.5130 634300 556688 238 979.387790 979.412193 0.16 22.59Macs_Tank 9621.5131 634400 556704 240 979.387230 979.412180 0.16 22.44 Macs_Tan k 9621.5132 634500 556720 241 979.387130 979.412168 0.16 22.55M acs_Tank 9621.5133 634600 556736 243 979.386840 979.412155 0.16 22.66 M acs_Tank 9621.5134 634700 556753 246 979.386230 979.412142 0.16 22.65M acs_Tank 9621.5135 634800 556769 252 979.385110 979.412130 0.16 22.73Macs_Tank 9621.5136 634900 556785 253 979.384120 979.412117 0.16 21.95Macs_Tank 9621.5137 635000 556801 263 979.381640 979.412105 0.16 21.45Macs_Tank 9621.5138 635100 556818 280 979.377890 979.412091 0.17 21.07Macs_Tank 9621.5139 635200 556834 288 979.376070 979.412079 0.16 20.82Macs_Tank 9621.5140 635300 556850 295 979.374520 979.412067 0.16 20.66Macs_Tank

Cymbric Vale Station # mE mN nuts! G obs Free Air TC BA/Line 9621.5001 632690 535740 360 979.366300 979.427335 0.42 10.23Cymbric 9621.5002 632788 535798 357 979.367080 979.427292 0.51 10.55Cymbric 9621.5003 632886 535857 346 979.369570 979.427249 0.78 11.19Cymbric 9621.5004 632984 535915 326 979.374390 979.427206 0.78 12.11Cymbric 9621.5005 633082 535974 303 979.379960 979.427162 1.59 14.01Cymbric 9621.5006 633179 536032 287 979.383510 979.427120 0.48 13.35Cymb ric 9621.5007 633277 536091 283 979.384620 979.427076 0.98 14.21Cymbric 9621.5008 633375 536149 285 979.384790 979.427033 0.71 14.55Cymbric 9621.5009 633473 536207 304 979.381450 979.426990 0.68 14.96Cymbric 9621.5010 633571 536266 317 979.379480 979.426947 0.32 15.23Cymbric 9621.5011 633669 536324 307 979.382110 979.426904 0.77 16.39Cymbric 9621.5012 633767 536383 282 979.388820 979.426860 0.30 17.75Cymbric 9621.5013 633865 536441 273 979.391210 979.426817 0.30 18.41Cymbric 9621.5014 633963 536499 262 979.393990 979.426774 0.29 19.06Cymbric 9621.5015 634061 536558 256 979.395570 979.426731 0.28 19.49Cymbric 9621.5016 634158 536616 249 979.397450 979.426688 0.27 20.03Cymbric 9621.5017 634256 536675 248 979.398260 979.426644 0.26 20.68Cymbric 9621.5018 634354 536733 247 979.398730 979.426602 0.26 20.99Cymbric 9621.5019 634452 536792 246 979.399780 979.426558 0.25 21.88Cymbric 9621.5020 634550 536850 246 979.400860 979.426515 0.24 22.99Cymbric 9621.5021 634643 536900 247 979.403130 979.426478 0.23 25.49Cymbric 9621.5022 634736 536951 244 979.401530 979.426440 0.23 23.33Cymbric 9621.5023 634828 537001 239 979.404920 979.426403 0.22 25.77Cymbric 9621.5024 634921 537052 237 979.405690 979.426366 0.21 26.17Cymbric 9621.5025 635014 537102 237 979.405900 979.426329 0.20 26.41Cymbric 9621.5026 635107 537153 238 979.405730 979.426291 0.19 26.46Cymbric 9621.5027 635200 537203 237 979.406170 979.426254 0.19 26.74Cymbric 9621.5028 635292 537253 238 979.406440 979.426217 0.18 27.24Cymbric 9621.5029 635385 537304 237 979.406930 979.426179 0.17 27.56Cymbric 9621.5030 635478 537354 237 979.407680 979.426142 0.16 28.33Cymbric 9621.5031 635571 537405 238 979.408180 979.426104 0.16 29.07Cymbric 9621.5032 635664 537455 242 979.407520 979.426067 0.15 29.22Cymbric 9621.5033 635756 537506 243 979.407450 979.426030 0.17 29.41Cymbric 9621.5034 635849 537556 246 979.406610 979.425992 0.16 29.18Cymbric 9621.5035 635942 537606 249 979.405890 979.425955 0.14 29.07Cymbric

Page 4 of 5 Appendix 1

Station # mE mN masl G obs Free Air TC BA/Line 9621.5036 636035 537657 246 979.406620 979.425918 0.15 29.26Cymbric 9621.5037 636128 537707 240 979.408330 979.425881 0.15 29.83Cymbric 9621.5038 636220 537758 238 979.409350 979.425843 0.12 30.46Cymbric 9621.5039 636313 537808 236 979.410150 979.425806 0.12 30.90Cymbric 9621.5040 636406 537859 233 979.410710 979.425768 0.11 30.90Cymbric 9621.5041 636499 537909 232 979.411000 979.425731 0.11 31.03Cymbric 9621.5042 636592 537959 230 979.411240 979.425694 0.10 30.90Cymbric 9621.5043 636685 538010 229 979.411720 979.425656 0.10 31.22Cymbric 9621.5044 636777 538060 229 979.412090 979.425619 0.10 31.63Cymbric 9621.5045 636870 538111 228 979.412410 979.425582 0.09 31.78Cymbric 9621.5046 636963 538161 227 979.412510 979.425545 0.08 31.71Cymbric 9621.5047 637056 538212 229 979.412080 979.425507 0.08 31.71Cymbric 9621.5048 637149 538262 231 979.411920 979.425470 0.09 31.99Cymbric 9621.5049 637241 538312 232 979.411330 979.425433 0.09 31.64Cymbric 9621.5050 637334 538363 235 979.410650 979.425395 0.07 31.57Cymbric 9621.5051 637427 538413 238 979.410030 979.425358 0.06 31.56Cymbric 9621.5052 637520 538464 238 979.410100 979.425320 0.06 31.67Cymbric 9621.5053 637613 538514 241 979.408860 979.425283 0.06 31.06Cymbric 9621.5054 637705 538565 244 979.408740 979.425245 0.06 31.57Cymbric 9621.5055 637798 538615 244 979.408370 979.425208 0.06 31.23Cymbric 9621.5056 637891 538666 239 979.409410 979.425171 0.06 31.33Cymbric 9621.5057 637984 538716 236 979.410250 979.425134 0.06 31.62Cymbric 9621.5058 638077 538766 235 979.410290 979.425097 0.06 31.50Cymbric 9621.5059 638169 538817 240 979.409400 979.425059 0.05 31.62Cymbric 9621.5060 638262 538867 237 979.409870 979.425022 0.05 31.53Cymbric 9621.5061 638355 538918 231 979.411070 979.424984 0.05 31.59Cymbric 9621.5062 638448 538968 229 979.411460 979.424947 0.06 31.63Cymbric 9621.5063 638541 539019 228 979.411740 979.424909 0.06 31.76Cymbric 9621.5064 638633 539069 227 979.411880 979.424872 0.05 31.73Cymbric 9621.5065 638726 539119 226 979.412110 979.424835 0.05 31.80Cymbric 9621.5066 638819 539170 226 979.411990 979.424797 0.05 31.71Cymbric 9621.5068 639005 539271 224 979.411970 979.424723 0.05 31.37Cymbric 9621.5069 639097 539321 224 979.411980 979.424686 0.05 31.42Cymbric 9621.5070 639190 539372 222 979.412170 979.424648 0.05 31.26Cymbric 9621.5071 639283 539422 222 979.412080 979.424611 0.05 31.20Cymbric 9621.5072 639376 539472 222 979.411920 979.424574 0.05 31.08Cymbric 9621.5073 639469 539523 222 979.411850 979.424536 0.05 31.05Cymbric 9621.5074 639561 539573 221 979.411860 979.424499 0.05 30.90Cymbric 9621.5075 639654 539624 221 979.411630 979.424461 0.05 30.71Cymbric 9621.5076 639747 539674 219 979.411670 979.424424 0.05 30.39Cymbric 9621.5077 639840 539725 218 979.411410 979.424386 0.05 29.97Cymbric 9621.5078 639933 539775 218 979.411190 979.424349 0.05 29.79Cymbric 9621.5079 640026 539825 217 979.411310 979.424312 0.05 29.75Cymbric 9621.5080 640118 539876 216 979.411360 979.424275 0.05 29.64Cymbric 9621.5081 640211 539926 216 979.411190 979.424237 0.05 29.51Cymbric 9621.5082 640304 539977 216 979.411100 979.424200 0.04 29.44Cymbric 9621.5083 640397 540027 216 979.410950 979.424163 0.04 29.33Cymbric 9621.5084 640490 540078 216 979.410800 979.424125 0.04 29.22Cymbric 9621.5085 640582 540128 216 979.410730 979.424088 0.04 29.19Cymbric 9621.5086 640675 540178 215 979.410670 979.424051 0.04 28.97Cymbric 9621.5087 640768 540229 215 979.410580 979.424013 0.04 28.91Cymbric 9621.5088 640861 540279 215 979.410530 979.423976 0.04 28.90Cymbric 9621.5089 640954 540330 214 979.410490 979.423938 0.04 28.70Cymbric 9621.5090 641046 540380 214 979.410510 979.423901 0.04 28.76Cymbric 9621.5091 641139 540431 214 979.410550 979.423863 0.04 28.84Cymbric 9621.5092 641232 540481 213 979.410690 979.423826 0.04 28.82Cymbric

Page 5 of 5 aim 1.00•0

Z4000'0 80000 ol co. N: (0 CC .- 0000000000 4000'0 1111111111

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ilwong 9g00•0 90000 Gne 8 8 8 ° c0 0 CO 0 11) 0 111 0 co 0 it) o o § CN .- C.) CO CM CV •-• r- &V CM .- Aouenbe.id AOUenbeJj Aouenbau Appendix 2

Values in SI

MAV Wehrlite on Conns Creek Macs Tank MUMC Thrust 50 25 i 45 40 0.8 >'35 'a' 30 0.6 g1:3• 25 2 20 0.4 U- 15 U- 5 0.2 10 5 0 o tO LII LO N CO fa 0 0 o o o 1 a d 2 ci a a k

Kayrunnera Gp 5 - 4.5 - 4 - 3.5 - Sands U 3 - C Muds a) = 2.5 - C. a) it 2 - 1.5 - 1 - 0.5 -

0 I 0.000002 0.000004 0.000006 0.000008 0.00001 0.00012 k

Gnalta Group Mootwingee Group 25 Cymbric Vale & Coonigan Fms 12 - 20 MWV - 10 -

it 4 - 2 -

0 i I 1 I I 0 § CO 0 (0 CM tl• o 0 N El! In LO N LO CO LO LO U/ CD 0 N 0 0 0 0 o E! 0 CM 0 CO 0 0 0 0 0 0 2 o o .c:7! a o 6 o 0 0 0 o ci o a o a a ci 2 k k

Page 2 of 3 • 0.00025 ,c• 0.00035 0.00015 0.00005 0.0004 0.0003 0.0002 0.0001 0.00008 0.00006 0.00004 0.00002 0.0001 More More o — IV C.34 iv Frequency Frequency CJ 4. cn in tri CD VCO V CO

dnorD sumoa e6i nvg uoneuuoj Aueci nea mAi

IS u! senlEA Appendix 3

Appendix 3 Summary density data

Area key: 1 = Nundora-Wonnaminta-Marrapina-Nuntherungie 2 = Mt Wright-Cymbric Vale; 3 = Grasmere; 4 = Scopes Range-Dolo Hills-DRL 5 = Adelaide Fold Belt; 6 = Glenelg Subzone; 7 = Smithton Trough

Sample Rocktype AREA Wet Mass Volume Density nund2 Nundorite 1 1233.2 498.5 2.474 nund Nundorite 1 723.2 288.5 2.507 Nsyenite syenite 1 1258.8 491.1 2.563 UM wehrlite 1 890.8 333.1 2.674 UM wehrlite 1 654.6 244.0 2.683 UM wehrlite 1 975.3 357.9 2.725 UM wehrlite 1 540.0 198.0 2.727 mavb4 basalt 1 633.1 232.0 2.729 BCDIORITE diorite 1 982.1 354.7 2.769 mavb basalt 1 762.5 274.7 2.776 mavb1 basalt 1 955.6 343.8 2.780 mavb2 basalt 1 1938.9 691.3 2.805 ?mafic wehrlite 1 890.2 317.3 2.806 D1 lamprophyre 1 1705.1 603.2 2.827 D2 lamprophyre 1 1045.5 368.9 2.834 GAB1 gabbro 1 1700.0 566.3 3.002 Rss sandstone 1 777.7 348.0 2.235 Rss sandstone 1 1055.1 471.0 2.240 K MS mudstone 1 285.0 125.3 2.275 R ss sandstone 1 547.9 240.3 2.280 K MS mudstone 1 485.1 211.7 2.291 Rss2 sandstone 1 861.4 375.9 2.292 RSS sandstone 1 758.2 329.2 2.303 Rss4 sandstone 1 1425.3 617.9 2.307 K MS mudstone 1 1033.8 446.5 2.315 Rss3 sandstone 1 406.1 174.2 2.331 K1.1 mudstone 1 1466.0 609.9 2.404 KARA SS sandstone 1 1624.9 656.6 2.475 KARA SS sandstone 1 503.2 201.9 2.492 TWSS sandstone 1 1628.2 621.7 2.619 KG1 sandstone 1 776.2 296.2 2.621 KG3 mudstone 1 915.4 347.6 2.633 KG2 mudstone 1 501.0 189.0 2.651 K ARK sandstone 1 518.5 195.5 2.652 LMS? limestone 1 633.2 233.4 2.713 ms .? mudstone 1 1842.6 748.5 2.462 Ponto ms schist 1 727.5 284.7 2.555 ponto2 schist 1 866.7 338.3 2.562 Ponto schist 1 757.5 293.2 2.584 pqm Qz-Mt rock 1 1250.7 477.8 2.618 pss1 sandstone 1 1389.7 526.6 2.639 Pss2 sandstone 1 1034.7 391.7 2.642 pssw1 sandstone 1 659.6 246.2 2.679 Ps sy syenite 1 552.8 208.9 2.646 MA ajc basalt 1 643.1 230.5 2.790 MA ajc basalt 1 540.4 191.0 2.829 MA ajc basalt 1 533.1 188.2 2.833 Ps sy syenite 1 753.6 282.1 2.671 Gab gabbro 1 1301.9 434.2 2.998 Ps sy syenite 1 1889.7 710.6 2.659 cm2 sandstone 1 853.3 321.2 2.657

Page 1 of 4 Appendix 3 Sample Rocktype AREA Wet Mass Volume Density 3ka2 mudstone 1 912.6 361.8 2.522 3ka1 mudstone 1 259.9 99.4 2.615 3ka3 mudstone 1 794.9 325.6 2.441 cm4 sandstone 1 465.7 180.0 2.587 cm1 sandstone 1 339.3 128.9 2.632 Ev1 basalt 1 479.3 179.0 2.678 ?Ev2 basalt 1 623.8 231.7 2.692 Doll dolerite 1 1262.3 427.2 2.955 MAV Tr trachyte 1 882.5 331.5 2.662 Gn 3 laterite 2 1613.2 619.4 2.604 Mp 2 schist 2 1115.9 424.0 2.632 Ponto? schist 2 1534.2 590.0 2.600 Gn1 laterite 2 1147.1 469.1 2.445 MWV2 basalt 2 792.4 291.4 2.719 OrdR sandstone 2 979.2 399.1 2.454 J?Qtzcgl laterite 2 1689.1 656.2 2.574 Bum 8 serpentinite 2 993.1 399.9 2.483 Mac10 serpentinite 2 1217.4 413.9 2.941 Mac3 serpentinite 2 1922.1 688.0 2.794 mac9 serpentinite 2 1605.7 647.7 2.479 bum7 serpentinite 2 1092.7 361.9 3.019 wum serpentinite 2 360.0 136.7 2.634 Gn2 laterite 2 1422.1 571.9 2.487 MWV1 basalt 2 1214.4 455.8 2.664 bum4 serpentinite 2 1952.0 651.3 2.997 wss1 sandstone 2 1130.2 419.0 2.697 CV2 2 884.5 323.1 2.738 wss2 sandstone 2 803.7 314.1 2.559 MWV2/1 basalt 2 -1304.0 0.000 wms mudstone 2 861.2 325.2 2.648 mac13 serpentinite 2 1779.5 740.8 2.402 mac20 serpentinite 2 974.1 388.0 2.511 mac17 serpentinite 2 1528.9 641.5 2.383 mac14 serpentinite 2 -1323.3 0.000 mac? serpentinite 2 1906.8 705.7 2.702 mac15 serpentinite 2 1240.7 568.9 2.181 mac18 serpentinite 2 1021.8 414.5 2.465 mac18b serpentinite 2 1350.0 542.2 2.490 mac8 serpentinite 2 1133.1 438.0 2.587 mac12(Cr ss) sandstone 2 1652.1 731.6 2.258 mac16 serpentinite 2 1527.8 648.7 2.355 mac2 serpentinite 2 1485.9 502.2 2.959 mac19 serpentinite 2 1658.3 696.4 2.381 mac19b serpentinite 2 1036.9 420.9 2.464 mac11 serpentinite 2 749.3 290.6 2.578 mac2b serpentinite 2 1044.5 395.7 2.640 mac5 serpentinite 2 1197.9 497.5 2.408 bu m5 serpentinite 2 480.0 205.8 2.332 bum8 serpentinite 2 1763.8 732.9 2.407 Pss sandstone 2 1586.2 612.9 2.588 pqm Qz-Mt rock 2 527.5 195.9 2.693 pqm Qz-Mt rock 2 570.6 211.1 2.703 pqm Qz-Mt rock 2 681.5 257.3 2.649 CRSS sandstone 2 1006.1 413.3 2.434 OrdR sandstone 2 1306.0 517.2 2.525 Pdyke lamprophyre 2 1471.5 535.3 2.749 Pss sandstone 2 1107.7 423.1 2.618

Page 2 of 4 Appendix 3

Sample Rocktype AREA Wet Mass Volume Density MWV2/1 basalt 2 1547.4 560.7 2.760 MWV2/1 basalt 2 668.2 243.2 2.748 Ponto(BarCk) schist 2 848.2 309.2 2.743 Ponto(BarCk) schist 2 611.8 223.8 2.734 Pdyke lamp rophyre 2 1625.1 589.9 2.755 Pdyke lamp rophyre 2 422.9 153.1 2.762 Wdio andesite 2 129.4 48.4 2.674 W'ss" andesite 2 558.6 211.3 2.644 mwv2 basalt 2 1045.1 391.0 2.673 wb8 basalt 2 464.3 172.8 2.687 wlms limestone 2 1073.2 400.1 2.682 wI2 limestone 2 1050.3 416.5 2.522 wlm limestone 2 1546.0 571.9 2.703 pcv4.1 amphibolite 2 1252.0 430.4 2.909 pcv2 amphibolite 2 689.4 227.9 3.025 pcv amphibolite 2 487.2 167.6 2.907 pcv3 amphibolite 2 531.1 183.6 2.893 cmwv1 basalt 2 1344.7 468.3 2.871 mwv3 basalt 2 848.5 315.0 2.694 mwv1 basalt 2 830.2 314.2 2.642 cmwv2 basalt 2 1179.0 421.7 2.796 cvt1 volcaniclastic 2 764.1 293.1 2.607 cvt2 volcaniclastic 2 803.2 307.1 2.615 cmwv3 basalt 2 488.8 170.5 2.867 wcv1 volcaniclastic 2 553.9 225.8 2.453 cvt3 volcaniclastic 2 1698.2 679.2 2.500 wcv5 volcaniclastic 2 545.3 213.4 2.555 wcv4 volcaniclastic 2 296.5 125.7 2.359 wm mudstone 2 481.1 180.7 2.662 wss sandstone 2 548.0 213.5 2.567 GR18 basalt 3 1488.5 507.2 2.935 GR34 basalt 3 1600.6 557.4 2.872 F (lapilli tuff?) volcaniclastic 3 933.3 333.8 2.796 Dio1 diorite 3 1001.0 335.1 2.987 H (dolerite) dolerite 3 659.4 221.6 2.976 J (gabbro) gabbro 3 769.3 262.0 2.936 G (basalt) basalt 3 435.3 • 146.6 2.969 I (basalt) basalt 3 417.9 142.0 2.943 INT?(mica ss) sandstone 3 290.2 108.2 2.682 QFP1 dolerite 3 1036.8 354.6 2.924 E (FSP) dolerite 3 1136.6 382.5 2.972 GR7 1.2m schist 3 573.6 217.2 2.641 GR7 203 schist 3 436.0 161.8 2.695 GR7 51 schist 3 290.3 107.3 2.705 GR7 57.5 schist 3 313.3 116.0 2.701 GR7 31.9 schist 3 280.8 104.5 2.687 TWSS crae 117m sandstone 4 358.1 133.3 2.686 TWSS crae 92m sandstone 4 462.1 172.3 2.682 Porphyry crae 103m rhyolite 4 206.7 78.9 2.620 Porphyry crae 70m rtiyolite 4 162.8 61.8 2.634 EHK3 181.6 monzogabbro 4 561.1 209.5 2.678 EHK3 207.1 monzogabbro 4 796.5 300.9 2.647 EHK3 184.3 monzogabbro 4 959.7 355.5 2.700 EHK2 194 monzogabbro 4 782.0 292.1 2.677 EHK2 180.6 monzogabbro 4 365.0 130.9 2.788 EHK3 131.6 monzogabbro 4 634.8 221.6 2.865 EHK3 173.7 monzogabbro 4 1015.5 380.3 2.670

Page 3 of 4 Appendix 3

Sample Rocktype AREA Wet Mass Volume Density EHK3 140.7 monzogabbro 4 808.8 279.2 2.897 EHK3 165.5 monzogabbro 4 433.3 162.0 2.675 EHK3 153.8 monzogabbro 4 716.2 249.7 2.868 EHK3 259.6 monzogabbro 4 1028.6 349.4 2.944 EHK1 129.0 monzogabbro 4 867.6 310.5 2.794 EHK3 137.1 monzogabbro 4 397.5 147.5 2.695 EHK3 305.3 monzogabbro 4 1158.9 403.0 2.876 EHK3 177.7 monzogabbro 4 1033.8 351.5 2.941 EHK3 125.8 monzogabbro 4 171.6 68.1 2.520 EHK1 109.5 monzogabbro 4 303.2 107.5 2.820 DL20 127.5 mudstone 4 856.5 314.7 2.722 DL20 116 mudstone 4 512.8 187.6 2.733 DL7 81 mudstone 4 338.3 122.2 2.768 DL19 119 mudstone 4 508.7 189.4 2.686 0L7 103 mudstone 4 398.4 143.1 2.784 DL20 133.1 mudstone 4 384.0 139.5 2.753 tr2a basalt 5 1526.3 527.6 2.893 tr2b basalt 5 1100.4 384.2 2.864 tr4a basalt 5 892.0 328.4 2.716 tr4b basalt 5 515.2 191.1 2.696 tr4c basalt 5 584.4 216.6 2.698 tr3 basalt 5 870.1 325.5 2.673 tr1 basalt 5 1325.1 464.3 2.854 Ja12 diorite 6 1538.4 544.5 2.825 Ja11 a diorite 6 244.8 93.2 2.627 Jail b diorite 6 314.4 120.2 2.616 MD4and b andesite 6 690.1 250.8 2.752 MD4and andesite 6 906.6 324.4 2.795 EL2 and andesite 6 1034.6 381.8 2.710 EL1 dacite 6 1178.5 430.9 2.735 MD3and andesite 6 1165.5 417.5 2.792 MD1and andesite 6 783.6 273.9 2.861 Be112 diorite 6 1005.5 360.0 2.793 Bell3a diorite 6 428.5 153.4 2.793 Bell3b diorite 6 293.2 104.4 2.808 MD2rhy rhyolite 6 580.0 218.5 2.654 MD2dac dacite 6 422.9 157.6 2.683 PLccb1 basalt 7 1644.3 541.7 3.035

35 - - 100.00% Histogram of all data - 90.00% 30 - - 80.00% EMS Frequency 25 - -a-Cumulative % - 70.00% - 60.00% - 50.00% - 40.00%

10 - - 30.00% - 20.00% - 10.00%

0 .00% 4:1 111 to IL) 03 Ci3 CM CM CM 0 CM CM CM CM 2 Bin

Page 4 of 4 Appendix 4 University of Tasmania School of Earth Sciences Rock Catalogue AMG coordinates are Zone 54 Cat. # Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139206 Ndt1 nundorite 6608499 600499 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS TS9600 139207 NUN2 nundorite 6608500 600500 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS 139208 TWSS sandstone 6600500 600800 Early-Middle Cambrian Teltawongee Gp R,TS TS9601 139209 LMS limestone 6619700 627700 Late Cambrian-Early Ordovician Kayrunnera Gp R,TS,CR,PD,P T59603 139210 PSSW1 sandstone 6613900 626500 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9604 139211 KG2 mudstone 6619007 628525 Mindyallan Kayrunnera Gp R,TS TS9605 139212 CRSS sandstone 6573030 628474 Tournaisian Ravendale Sandstone R,TS TS9606 139213 PSS2 sandstone 6610400 634300 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9607 139214 KG3 mudstone 6619007 628525 -Mindyallan Kayrunnera Gp R,TS TS9608 139215 TS9609;Kark sandstone 6608825 621154 Cambrian Nundora Fm R,TS zrc date 139216 NSY syenite 6605800 605385 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS TS9611 139217 KG1 sandstone 6613281 636150 Mindyallan Kayrunnera Gp R,TS TS9610 139218 PQM1 Qz-Mt rock 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9612 139219 BCDiorite diorite 6583500 659800 Late Cambrian-Early Ordovician Gneilwonga Intrusive suite R,TS,PD TS9613 139220 GAB1 gabbro 6613316 625364 Late Cambrian-Early Ordovician Gneilwonga Intrusive suite R,TS,PD TS9615 139221 ?P Dyke B lamprophyre 6609861 634637 Permian R,TS,PD TS9616 139222 P Dyke A lamprophyre 6609861 634637 Permian R,TS,PD 139223 D1 lamprophyre 6613815 626825 Permian R,TS,PD TS9617 139224 MAVb basalt 6605220 607017 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS TS9618 139225 D2 lamprophyre 6613815 626825 Permian R,TS,PD TS9619 139226 PSSY syenite 6616417 593514 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS TS9620 139227 BUM dolerite 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC R,TS TS9621 139228 W MS mudstone 6543900 641400 Early-Middle Cambrian Gnalta Gp R,TS TS9622 139229 BUM 2 basalt 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC R,TS TS9623 139230 MW LMS limestone 6538500 634300 Early-Middle Cambrian Gnalta Gp R,TS TS9624 139231 BUM 4 basalt 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC R,TS TS9625 139232 WSS1 sandstone 6543900 641400 Early-Middle Cambrian Gnalta Gp R,TS,PD TS9626 139233 WD diorite 6543900 641400 Early- Middle Cambrian Gnalta Gp R,TS TS9627 139234 GN2 silcrete 6563591 626954 Recent R,TS TS9630 139235 WSS sandstone 6543900 641400 Early-Middle Cambrian Gnalta Gp R,TS TS9632 139236 MWV 2/1 basalt 6538500 634300 Early-Middle Cambrian Gnalta Gp R,TS TS9634

Page 1 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139237 Mac 10 basalt 6557200 634000 Late Cambrian-Early Ordovician Macs Tank MUMC R,TS TS9635 139238 MWV 2 dolerite 6538500 634300 Early-Middle Cambrian Mt Wright Volcanics R,TS TS9636 139239 BUM 1 basalt 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC R,TS TS9637 139240 Mac 6 basalt 6556500 633500 Late Cambrian-Early Ordovician Macs Tank MUMC R,PS TS9638 139241 Bum 7 basalt 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC R,TS TS9639 139242 Mac 18 serpentinite 6555000 632700 Late Cambrian-Early Ordovician Macs Tank MUMC R,PS TS9640 139243 AJC126 basalt 6556500 633500 Late Cambrian-Early Ordovician Macs Tank MUMC PS TS9637 139244 AJC124A basalt 6556500 633500 Late Cambrian-Early Ordovician Macs Tank MUMC PS TS9638 139245 Ponto cc schist 6539877 634916 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9641 139246 DL19 117.7m sandstone 6471250 654980 Cambrian Teltawongee Gp R,TS TS9643 139247 DL20 92.5m sandstone 6471250 655200 Cambrian Teltawongee Gp R,TS TS9644 139248 DL19 103.5 m rhyolite 6471250 654980 Late Cambrian-Early Ordovician Dolo rhyolite R,TS TS9645 139249 DL20 70m rhyolite 6471250 655200 Late Cambrian-Early Ordovician Dolo rhyolite R,TS TS9646 139250 Wb2 dole rite 6546108 638550 Early-Middle Cambrian Gnalta Gp R,TS,PD TS9701 139251 Wb3 basalt 6546108 638550 Early-Middle Cambrian Gnalta Gp R,TS,PD TS9702 139252 Wb4 basalt 6546205 638613 Early-Middle Cambrian Gnalta Gp R,TS TS9703 139253 Wb5 basalt 6546282 638508 Early-Middle Cambrian Gnalta Gp R,TS TS9704 139254 Wb6 dolerite 6546245 638468 Early-Middle Cambrian Gnalta Gp R,TS TS9705 139255 Wb7 dolerite 6546245 638468 Early-Middle Cambrian Gnalta Gp R,TS,P D TS9706 139256 Wb8 basalt 6546489 638540 Early-Middle Cambrian Gnalta Gp R,TS TS9707 139257 Wm2 dolerite 6546108 638550 Early-Middle Cambrian Gnalta Gp R,TS,P D TS9708 139258 Pd1 dole rite 6546160 638365 Late Cambrian-Early Ordovician Ponto Complex R,TS,P D TS9709 139259 PCV2 basalt 6545945 635755 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9710 139260 PCV3 basalt 6546067 635940 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9711 139261 PCV4 basalt 6546067 635940 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9712 139262 PCV5 basalt 6546399 635924 Late Cambrian-Early Ordovician Ponto Complex R,TS,PD TS9713 139263 PCV6 basalt 6546399 635924 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9714 139264 PCV1 basalt 6545933 635712 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9715 139265 MVVV1 basalt 6549358 632963 Early-Middle Cambrian Mt Wright Volcanics R,TS TS9716 R,TS TS9717 139266 MWV2 basalt 6549300 632922 Early- Middle Cambrian Mt Wright Volcanics 139267 MWV3 basalt 6549179 632794 Early-Middle Cambrian Mt Wright Volcanics R,TS TS9718 139268 "WLMS" dolerite 6546065 638671 Early-Middle Cambrian Gnalta Gp R,TS,PD TS9719 139269 Fl a dolerite 6614974 625648 Late Cambrian-Early Ordovician Teltawongee Gp R,TS,P D TS9724

Page 2 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139270 Fib siltstone 6614974 625648 Cambrian Teltawongee Gp R,TS TS9725 139271 F2 siltstone 6614597 625824 Cambrian Teltawongee Gp R,TS TS9726 139272 F3 siltstone 6614655 625960 Cambrian Teltawongee Gp R,TS TS9727 139273 F4 siltstone 6614648 626172 Cambrian Teltawongee Gp R,TS TS9728 139274 F4b siltstone 6614648 626172 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9729 139275 F5 siltstone 6614848 626262 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9730 139276 F6 siltstone 6614933 626521 Late Cambrian-Early Ordovician Ponto Complex R,TS TS9731 139277 F7 siltstone 6614967 626749 Late Cambrian-Early Ordovician Ponto Complex FLTS TS9732 139278 wq quartzite 6545675 639096 Late Neoproterozoic Gnalta Gp R,TS TS9733 139279 wss3 sandstone 6545675 639096 Early-Middle Cambrian Gnalta Gp R,TS TS9734 139280 WLM limestone 6546065 638671 Early-Middle Cambrian Gnalta Gp R,TS,CR,PD,P TS9735 139281 WL2 limestone 6546226 638623 Early-Middle Cambrian Gnalta Gp R,TS,PD,P TS9736 139282 ONSS1 sandstone 6548147 627401 Late Cambrian-Early Ordovician Nootumbulla Sandstone R,TS TS9737 139283 MM 1 L-S tectonite 6542522 635398 Early-Middle Cambrian Gnalta Gp R,TS TS9738 139284 MM5 L-S tectonite 6542522 635398 Early-Middle Cambrian Gnalta Gp R,TS TS9739 139285 A L-S tectonite 6537216 636087 Early-Middle Cambrian Gnalta Gp R,TS TS9740 139286 B1 L-S tectonite 6537216 636087 Early-Middle Cambrian Gnalta Gp R,TS TS9741 139287 L-S tectonite 6537216 636087 Early-Middle Cambrian Gnalta Gp R,TS TS9742 139288 L-S tectonite 6537216 636087 Early-Middle Cambrian Gnalta Gp R,TS TS9743 139289 CVT1 sandstone 6550301 633464 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9744 139290 CVT2 siltstone 6549167 632762 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9745 139291 CVT3 sandstone 6548916 632244 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9746 139292 CVN1 v'clastic sst 6550900 633800 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9747 139293 CVN2 v'clastic sst 6550900 633800 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9748 139294 CVN3 v'clastic sst 6550900 633800 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9749 139295 CVN4 v'clastic sst 6550900 633800 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9750 139296 CVN5 siltstone 6550900 633800 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9751 139297 WCV1 sandstone 6547754 626948 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9752 139298 WCV2 sandstone 6547754 626948 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9753

139299 WCV3 sandstone 6547754 626948 Early- Middle Cambrian Cymbric Vale Fm R,TS TS9754 139300 WCV4 sandstone 6547754 626948 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9755 139301 WCV5 sandstone 6547754 626948 Early-Middle Cambrian Cymbric Vale Fm R,TS TS9756 139302 9801 sandstone 6581638 629209 Late Silurian-Early Devonian Mt Daubeny Fm R,TS

Page 3 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139303 9802 shale 6528123 658208 Late Neoproterozoic Kara beds R,TS 139304 9803 sandstone 6528108 658367 Cambrian Teltawongee Gp R,TS 139305 9804 sandstone 6528270 658431 Cambrian Teltawongee Gp R,TS 139306 9806 sandstone 6528676 659164 Cambrian Teltawongee Gp R,TS 139307 9807 shale 6529210 660230 Late Neoproterozoic Kara beds R,TS 139308 9808 phyllite 6529268 660282 Late Cambrian-Early Ordovician Ponto Complex R,TS 139309 9809 diorite 6606261 630741 Late Cambrian-Early Ordovician Gneilwonga Intrusive Suite R,TS,PD 139310 9810 sandstone 6603017 637082 Late Cambrian-Early Ordovician Teltawongee Gp R,TS 139311 9812 sandstone 6603282 637797 Late Cambrian-Early Ordovician Ponto Complex R,TS 139312 9813 sandstone 6614360 624818 Late Cambrian-Early Ordovician Teltawongee Gp R,TS 139313 9814 dolerite 6614880 625493 Late Cambrian-Early Ordovician Gneilwonga Intrusive Suite R,TS,P D 139314 9830 siltstone 6712000 549900 Cambrian Teltawongee Gp R,TS 139315 9831 siltstone 6712000 549900 Cambrian Teltawongee Gp R,TS 139316 9832 sandstone 6712000 551800 Cambrian Teltawongee Gp R,TS 139317 9833 siltstone 6728300 557950 Cambrian Teltawongee Gp R,TS 139318 9834 siltstone 6728300 557950 Cambrian Teltawongee Gp R,TS 139319 9835 dolerite 6538631 660778 Late Cambrian-Early Ordovician Ponto Complex R,TS,PD 139320 9836 basalt 6536583 661625 Late Cambrian-Early Ordovician Ponto Complex R,TS 139321 9837 basalt 6536583 661625 Late Cambrian-Early Ordovician Ponto Complex R,TS 139322 9838 basalt 6535000 664726 Late Cambrian-Early Ordovician Ponto Complex R,TS 139323 9839 basalt 6535000 664726 Late Cambrian-Early Ordovician Ponto Complex R,TS 139324 9840 dolerite 6535206 664700 Late Cambrian-Early Ordovician Ponto Complex R,TS,PD 139325 9841 v'clastic sst 6535206 664700 Late Cambrian-Early Ordovician Ponto Complex R,TS 139326 9842 basalt 6535206 664700 Late Cambrian-Early Ordovician Ponto Complex R,TS 139327 9843 dolerite 6536715 664505 Late Cambrian-Early Ordovician Ponto Complex R,TS 139328 9844 basalt 6537136 663563 Late Cambrian-Early Ordovician Ponto Complex R,TS 139329 9845 gabbro 6537702 662276 Late Cambrian-Early Ordovician Ponto Complex R,TS,PD 139330 9846 basalt 6542327 635180 Late Cambrian-Early Ordovician Ponto Complex R,TS 139331 9847 schist 6542403 635324 Late Cambrian-Early Ordovician Ponto Complex R,TS 139332 9849 basalt 6542432 635548 Late Cambrian - Early Ordovician Ponto Complex R,TS 139333 9850 L-S tectonite 6542236 635299 Late Cambrian-Early Ordovician Gnalta Gp R,TS 139334 9851 sandstone 6545814 643685 Cambrian Teltawongee Gp R,TS 139335 9852 sandstone 6545825 643735 Cambrian Teltawongee Gp R,TS

Page 4 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139336 9853 shale 6545541 641352 Late Neoproterozoic Kara beds R,TS 139337 9854 tuff 6632758 619907 Late Cambrian-Early Ordovician Ponto Complex R,TS 139338 9855 tuff 6632379 619740 Late Cambrian-Early Ordovician Ponto Complex R,TS 139339 9856 basalt 6632293 619433 Late Cambrian-Early Ordovician Ponto Complex R,TS 139340 9857 Qz-Mt rock 6632196 619352 Late Cambrian-Early Ordovician Ponto Complex R,TS 139341 9858 sandstone 6631357 618696 Late Cambrian-Early Ordovician Ponto Complex R,TS 139342 9859 tuff 6631684 617950 Late Cambrian-Early Ordovician Ponto Complex R,TS 139343 9860 sandstone 6631693 617160 Late Cambrian-Early Ordovician Ponto Complex R,TS 139344 9861 tuff 6631622 617074 Late Cambrian-Early Ordovician Ponto Complex R,TS 139345 9862 basalt 6631486 616803 Late Cambrian-Early Ordovician Ponto Complex R,TS,PD 139346 9863 sandstone 6661588 557344 Late Cambrian-Early Ordovician Pincally Fm R,TS 139347 9864 sandstone 6661588 557344 Late Cambrian-Early Ordovician Pincally Fm R,TS,P D 139348 9865 sandstone 6661573 557330 Late Cambrian-Early Ordovician Pincally Fm R,TS,P D 139349 9866 basalt 6669200 555956 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS,PD 139350 9867 basalt 6669200 555956 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS,P D 139351 9868 trachyandesite 6669081 562010 Late Neoproterozoic Mt Arrowsmith Volcanics R,TS 139352 9869 wood 6674948 558280 Cretaceous Rolling Downs Gp R,TS 139353 9870 shale ?? ?? Ordovician Dullingari Gp R,TS 139354 9815 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139355 9816 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139356 9817 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139357 9818 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139358 9819 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139359 9820 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139360 9821 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139361 9822 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139362 9823 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139363 9824 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139364 9825 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139365 9826 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139366 9827 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139367 9828 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS 139368 9829 phyllite 6535425 663035 Late Cambrian-Early Ordovician Ponto Complex R,TS

Page 5 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139369 9871 andesite 5896963 640380 Late Cambrian Dryden Suite R,TS 139370 9872 rhyolite 5896687 640267 Late Cambrian Dryden Suite R,TS 139371 9873 dacite 5896687 640267 Late Cambrian Dryden Suite R,TS 139372 9874 andesite 5897399 640660 Late Cambrian Dryden Suite R,TS,PD 139373 9875 dacite 5897480 640847 Late Cambrian Dryden Suite R,TS 139374 9876 andesite 5897480 640847 Late Cambrian Dryden Suite R,TS 139375 9877 diorite 5880803 649913 Late Cambrian Dryden Suite R,TS 139376 9878 diorite 5880803 649913 Late Cambrian Dryden Suite R,TS,PD 139377 9879 diorite 5880803 649913 Late Cambrian Dryden Suite R,TS 139378 9880 diorite 5880767 649827 Late Cambrian Dryden Suite R,TS 139379 9881 diorite 5880777 649827 Late Cambrian Dryden Suite R,TS,PD 139380 9883 andesite lava 5849274 647134 Late Cambrian Dryden Suite R,TS 139381 9884 andesite 5849517 647021 Late Cambrian Dryden Suite R,TS 139382 FP1 boninite 5883643 650841 Middle-Late Cambrian Frying Pan Suite R,TS,PD 139383 FP2 boninite 5883643 650841 Middle-Late Cambrian Frying Pan Suite R,TS,PD 139384 FP3 boninite 5883643 650841 Middle-Late Cambrian Frying Pan Suite R,TS,PD 139385 FP4 boninite 5884029 650716 Middle-Late Cambrian Frying Pan Suite 139386 FP5 boninite 5884029 650716 Middle-Late Cambrian Frying Pan Suite 139387 FP6 boninite 5884029 650716 Middle-Late Cambrian Frying Pan Suite 139388 YANS1 256m picrite 5990627 538195 Late Neoproterozoic Yanac South Suite R,PD,TS 139389 YANS1 279m picrite 5990627 538195 Late Neoproterozoic Yanac South Suite R,CR,PD,TS,PB 139390 YANS1 299m picrite 5990627 538195 Late Neoproterozoic Yanac South Suite R,PD,TS 139391 VIMP6 221.7 serpentinite 5980000 596500 Middle-Late Cambrian Kalkee Domain R,CR,PD 139392 VIMP6 216.0 serpentinite 5980000 596500 Middle-Late Cambrian Kalkee Domain R,CR,PD 139393 VIMP6 212.3 serpentinite 5980000 596500 Middle-Late Cambrian Kalkee Domain R,CR,PD 139394 VIMP6 232.5 serpentinite 5980000 596500 Middle-Late Cambrian Kalkee Domain R,PD 139395 VIMP6 229.8 serpentinite 5980000 596500 Middle-Late Cambrian Kalkee Domain R,PD 139396 YANS2 224.4 serpentinite 5987920 540900 Late Neoproterozoic Yanac South Suite R,CR,PD,TS 139397 YANS2 243.2 serpentinite 5987920 540900 Late Neoproterozoic Yanac South Suite R,CR,PD,TS 139398 JAL1A dacite 5875280 649853 Late Cambrian Dryden Suite 139399 JAL1B dacite 5875280 649853 Late Cambrian Dryden Suite 139400 JAL2 dacite 5875390 650178 Late Cambrian Dryden Suite 139401 9885 basalt 6532800 662600 Late Cambrian-Early Ordovician Ponto Complex R,TS

Page 6 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139402 9886 basalt 6532000 664300 Late Cambrian-Early Ordovician Ponto Complex R,TS 139403 9887 schist 6537340 637600 Late Cambrian-Early Ordovician Ponto Complex R,TS 139404 9888 schist 6538024 637190 Late Cambrian-Early Ordovician Ponto Complex R,TS 139405 EHK1 109.5 monzogabbro 6411720 556640 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS,PD 139406 EHK1 129 monzogabbro 6411720 556640 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139407 EHK2 180.6 monzogabbro 6398390 543400 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS,PD 139408 EHK2 194 monzodiorite 6398390 543400 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS,PD 139409 DL20 70 rhyolite 6712000 551800 Late Cambrian-Early Ordovician Dolo rhyolite R,TS,PD 139410 DL19 104.5 rhyolite 6712000 549900 Late Cambrian-Early Ordovician Dolo rhyolite R,TS 139411 DL19 126.8 rhyolite 6712000 549900 Late Cambrian-Early Ordovician Dolo rhyolite R,TS,PD 139412 DL19 52.6 rhyolite 6712000 549900 Late Cambrian-Early Ordovician Dolo rhyolite R,TS 139413 DL19 59 rhyolite 6712000 549900 Late Cambrian-Early Ordovician Dolo rhyolite R,TS 139414 EHK3 131.6 hbl andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139415 EHK3 137.1 hbl andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS,PD 139416 EHK3 140.7 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139417 EHK3 153.8 dolerite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk tholeiitic suite R,TS,PD 139418 EHK3 165.5 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139419 EHK3 173.7 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139420 EHK3 177.7 dolerite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk tholeiitic suite R,TS,PD 139421 EHK3 181.6 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139422 EHK3 184.3 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139423 EHK3 207.1 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS,PD 139424 EHK3 259.6 andesite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk calc-alkaline suite R,TS 139425 EHK3 305.3 dolerite 6419400 565150 Late Cambrian-Early Ordovician Eaglehawk tholeiitic suite R,TS,PD 139426 WAH 827.4 basalt 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS,PD 139427 WAH 838.5 basalt 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS,PD 139428 WAH 848 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139429 WAH 873 monzodiorite 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS,PD 139430 WAH 919 syenite 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139431 WAH 924 syenite 6463500 584500 Late Cambrian - Early Ordovician Wahratta calc - alkaline suite R,TS 139432 WAH 973.9 syenite 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139433 WAH 986.5 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS,PD 139434 WAH 995 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS,PD

Page 7 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139435 WAH 1000 dolerite 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS 139436 WAH 1031 dolerite 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS 139437 WAH 1034 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139438 WAH 1037 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139439 WAH 1043 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139440 WAH 1050 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139441 WAH 1053 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS,P D 139442 WAH 1055 dolerite 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS,PD 139443 WAH 1058 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139444 WAH 1060 monzogabbro 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139445 WAH 1066 dolerite 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS 139446 WAH 1081 dolerite 6463500 584500 Late Cambrian-Early Ordovician Wahratta tholeiitic suite R,TS,PD 139447 WAH 956 syenite 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139448 WAH SY syenite 6463500 584500 Late Cambrian-Early Ordovician Wahratta calc-alkaline suite R,TS 139449 MAVB1 basalt 605220.5 607018 Late Neoproterozoic Mt Arrowsmith Volcanics 139450 MAVB2 basalt 605220.5 607018 Late Neoproterozoic Mt Arrowsmith Volcanics 139451 MAVB4 basalt 605220.5 607018 Late Neoproterozoic Mt Arrowsmith Volcanics 139452 MAV UM wehrlite 605220.5 607018 Late Neoproterozoic Mt Arrowsmith Volcanics 139453 K1.1 siltstone 6606966 613726 Late Neoproterozoic Kara beds 139454 KASS sandstone 6608825 621154 Late Neoproterozoic Kara beds 139455 DL19 119 sandstone 6712000 549900 Cambrian Teltawongee Gp 139456 DL20 127.5 sandstone 6712000 551800 Cambrian Teltawongee Gp 139457 KMS mudstone 6613221 619705 Late Neoproterozoic Kara beds 139458 PontoSS sandstone 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex 139459 PontoSS2 sandstone 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex 139460 PontoSS3 sandstone 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex 139461 Silcrete silcrete 6544000 638000 ?Cretaceous Rolling Downs Gp 139462 Rowena1 sandstone 6537000 634000 Late Cambrian-Early Ordovician Rowena Fm 139463 Rowena2 sandstone 6537000 634000 Late Cambrian-Early Ordovician Rowena Fm 139464 Bynguano1 sandstone 6536000 632000 Late Cambrian - Early Ordovician Bynguano Sandstone Mbr 139465 Bynguano2 sandstone 6536000 632000 Late Cambrian-Early Ordovician Bynguano Sandstone Mbr 139466 Ravendale1 sandstone 6573264 628772 Tournaisian Ravendale Sandstone 139467 MAC11 sandstone 6557200 634000 Late Cambrian-Early Ordovician Ravendale Sandstone

Page 8 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139468 TR1 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R,TS,PD 139469 TR2 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R,TS,CR,PD 139470 TR3 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R,TS 139471 TR4 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R,TS 139472 TR5 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R 139473 TR6 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R 139474 TR7 basalt 6203514 380195 Late Neoproterozoic Truro Volcanics R 139475 N-alpha shale 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139476 beta siltstone 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139477 epsilon(N) siltstone 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139478 N-xi siltstone 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139479 N-eta siltstone 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139480 Ni shale 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139481 N2 shale 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139482 N3 siltstone 6078687 257724 Late Neoproterozoic Heatherdale Shale R 139483 3Ka1 siltstone 6600250 600832 Late Neoproterozoic Kara beds R 139484 3Ka2 sandstone 6600250 600832 Late Neoproterozoic Kara beds R 139485 3Ka3 sandstone 6600250 600832 Late Neoproterozoic Kara beds R 139486 2F sandstone 6600270 600993 Cambrian Nundora Fm R 139487 3B sandstone 6600250 600832 Cambrian Nundora Fm R,TS,PD,H 139488 3C sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139489 3D sandstone 6600250 600832 Cambrian Nundora Fm R,TS,PD,H 139490 3E sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139491 3F sandstone 6600250 600832 Cambrian Nundora Fm R,TS,PD,H 139492 3G sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139493 3H sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139494 31 sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139495 3J sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139496 3K sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139497 3L sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139498 3N sandstone 6600250 600832 Cambrian Nundora Fm R,TS

139499 3N1 sandstone 6600250 600832 . Cambrian Nundora Fm R,TS 139500 3N2 sandstone 6600250 600832 Cambrian Nundora Fm R,TS

Page 9 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139501 30 sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139502 3P sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139503 3P1 sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139504 3Q2 sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139505 3Q3 sandstone 6600250 600832 Cambrian Nundora Fm R,TS 139506 1A shale 6600266 600977 Cambrian Nundora Fm R 139507 1C sandstone 6600266 600977 Cambrian Nundora Fm R 139508 10 sandstone 6600266 600977 Cambrian Nundora Fm R 139509 1F sandstone 6600266 600977 Cambrian Nundora Fm R 139510 1L sandstone 6600266 600977 Cambrian Nundora Fm R 139511 CM1 sandstone 6581449 657627 Cambrian Copper Mine Range Fm R,TS 139512 CM2 sandstone 6581391 657681 Cambrian Copper Mine Range Fm R,TS 139513 CM3 sandstone 6581388 657813 Cambrian Copper Mine Range Fm R,TS 139514 CM4 sandstone 6581285 657797 Cambrian Copper Mine Range Fm R,TS 139515 CM5 sandstone 6581329 657771 Cambrian Copper Mine Range Fm R,TS 139516 CM6 sandstone 6581356 657757 Cambrian Copper Mine Range Fm R,TS 139517 CM7 sandstone 6581356 657757 Cambrian Copper Mine Range Fm R,TS 139518 KA1 sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139519 KA2 sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139520 KB sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139521 KC sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139522 KD sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139523 KD2 sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139524 KE sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139525 KF2/1 sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139526 KF2/2 sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139527 KF sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr PD,TS 139528 KI sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139529 KK sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139530 KL sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139531 KN sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139532 KO sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139533 KP sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr H,TS mz date

Page 10 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139534 KR sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139535 KT sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139536 KU sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139537 KV sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139538 KW sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139539 KX sandstone 6078687 257724 Early Cambrian Madigan Inlet Mbr R,TS 139540 001 142-144 diorite 6441945 603180 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139541 001 156-158 diorite 6441945 603180 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139542 002 136-137 andesite 6443000 603320 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139543 002 137-138 andesite 6443000 603320 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139544 002 144-145 andesite 6443000 603320 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139545 004 158-160 diorite 6444880 603510 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139546 005 174-176 andesite 6451400 607080 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139547 005 178-180 andesite 6451400 607080 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139548 005 188-190 diorite 6451400 607080 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139549 005 198-200 diorite 6451400 607080 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139550 006 162-164 phyllite 6446205 603705 Late Cambrian-Early Ordovician Ponto Complex CH,TS,PD 139551 006 172-174 dolerite 6446205 603705 Late Cambrian-Early Ordovician Inkerman tholeiitic suite CH,TS,PD 139552 006 188-190 phyllite 6446205 603705 Late Cambrian-Early Ordovician Ponto Complex CH,TS,PD 139553 007 132-134 andesite 6468980 627705 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139554 007 150-152 andesite 6468980 627705 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139555 007 178-180 diorite 6468980 627705 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139556 008 42-44 dacite 6463700 633380 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139557 008 48-50 andesite 6463700 633380 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139558 008 50-52 andesite 6463700 633380 Late Cambrian-Early Ordovician Inkerman calc-alkaline suite CH,TS,PD 139559 008 58-60 andesite 6463700 633380 Late Cambrian-Early Ordovician lnkerman calc-alkaline suite CH,TS,PD 139560 PCV L-S tectonite 6545933 635715 Late Cambrian-Early Ordovician Ponto Complex 139561 Ponto X-Loc phyllite 6537350 636900 Late Cambrian-Early Ordovician Ponto Complex 139562 Ponto phyllite 6537350 636900 Late Cambrian-Early Ordovician Ponto Complex 139563 M P2 phyllite 6537350 636900 Late Cambrian-Early Ordovician Ponto Complex 139564 BUM9 serpentinite 6537350 636900 Late Cambrian-Early Ordovician Baroorangee Creek MUMC 139565 Ponto2 tuff 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex 139566 Ponto2A tuff 6610434 633716 Late Cambrian-Early Ordovician Ponto Complex

Page 11 of 12 Cat.# Field# rock name mN mE Biostratigraphy Lithostratigraphy Preps Comments 139567 M1 phyllite 6537350 636900 Late Cambrian-Early Ordovician Ponto Complex 139568 MAC serpentinite 6556500 633500 Late Cambrian-Early Ordovician Macs Tank MUMC 139569 MWV2 basalt 6549200 632800 Early-Middle Cambrian Mt Wright Volcanics 139570 MWV3 basalt 6549200 632800 Early-Middle Cambrian Mt Wright Volcanics 139571 TT2 L-S tectonite 6542236 635299 Early-Middle Cambrian Gnalta Gp 139572 MWVPk basalt 6549200 632800 Early-Middle Cambrian Mt Wright Volcanics 139573 MW-MWV basalt 6549200 632800 Early-Middle Cambrian Mt Wright Volcanics 139574 CMWV1 basalt 6546801 632509 Early-Middle Cambrian Mt Wright Volcanics 139575 CMWV2 basalt 6546925 632551 Early-Middle Cambrian Mt Wright Volcanics 139576 CMWV3 basalt 6546975 632550 Early-Middle Cambrian Mt Wright Volcanics 139577 CMWV4 basalt 6547166 632617 Early-Middle Cambrian Mt Wright Volcanics

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Direen N. G. 1998. The Palaeozoic Koonenberry Fold and Thrust Belt, far western New South Wales: a case study in applied gravity and magnetic modelling. Exploration Geophysics 29, 330-339.