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Fig. 3. Photomicrographs of microstructures in eclogite from the Collingwood River (Tasmania). Mineral symbols after Kretz (1983) and Phe for phengite. (A) Euhedral porphyroblastic garnet with abundant inclusions in a partly retrogressed matrix. Crossed nicols, sample RCOG11. (B) Fine-grained layer showing textural equilibrium among Grt, Omp. Cam, and Ep. Crossed nicols, sample RO380. (C) Backscattered scanning electron microscope (BSE-SEM) image showing the good textural equilibrium among the mineral phases defining the eclogite facies stage III. Sample RO380. (D) Porphyroblastic garnet and the Di+Pl symplectite after omphacite. Crossed nicols, sample RCO611. (E) BSE-SEM image of a phengite relic surrounded by its destabilization products (Bt +P symplectite). Sample RO380. (F) Anhedral garnet relics, together with abundant porphyroblastic amphiboles. Crossed nicols, sample RO289. (G) BSE image of a porphyroblastic amphibole with a garnet relic as inclusion. Sample RO380. (H) BSE image of a late vein cross-cutting a porphyroblastic amphibole. The vein consists of an association of chlorite, tremolite, and calcite. Sample RO380.

Figure 3 Photomicrographs of microstructures in eclogite from the Collingwood River (Tasmania). Mineral symbols after Kretz (1983) and Phe for phengite. (A) Euhedral porphyroblastic garnet with abundant inclusions in a partly retrogressed matrix. Crossed nicols, sample RCOG11. (B) Fine-grained layer showing textural equilibrium among Grt, Omp. Cam, and Ep. Crossed nicols, sample RO380. (C) Backscattered scanning electron microscope (BSE-SEM) image showing the good textural equilibrium among the mineral phases defining the eclogite facies stage III. Sample RO380. (D) Porphyroblastic garnet and the Di+Pl symplectite after omphacite. Crossed nicols, sample RCO611. (E) BSE-SEM image of a phengite relic surrounded by its destabilization products (Bt +P symplectite). Sample RO380. (F) Anhedral garnet relics, together with abundant porphyroblastic amphiboles. Crossed nicols, sample RO289. (G) BSE image of a porphyroblastic amphibole with a garnet relic as inclusion. Sample RO380. (H) BSE image of a late vein cross-cutting a porphyroblastic amphibole. The vein consists of an association of chlorite, tremolite, and calcite. Sample RO380.

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ana In Tasmania, the Neoproterozoic-Cambrian metamorphic rocks involved in the Tyennan Orogeny are confined to the western and northern areas (Fig. 1C). In western Tasmania, the Neoproterozoic-early Tasmania is a key region located between the Cambro-Ordovician rocks of the Ross Orogen in Northern Victoria Land and the Lachlan Fold Belt in southern mainland Australia (Fig. 1A, B, C). In addition, these three Fig. 1. (A) Configuration of Antarctica, Australia, and Tasmania during Cambro-Ordovician times (modified after Foden et al., 2006); (B) tectonic sketch map showing the different structural zones of Northern Victoria Land (Antarctica), Tasmania, and southeast Australia (after Fl6ttmann et al., 1993, Foden et al., 2006); (C) geological map of western Tasmania (modified after Meffre et al., 2000).
ana In Tasmania, the Neoproterozoic-Cambrian metamorphic rocks involved in the Tyennan Orogeny are confined to the western and northern areas (Fig. 1C). In western Tasmania, the Neoproterozoic-early Tasmania is a key region located between the Cambro-Ordovician rocks of the Ross Orogen in Northern Victoria Land and the Lachlan Fold Belt in southern mainland Australia (Fig. 1A, B, C). In addition, these three Fig. 1. (A) Configuration of Antarctica, Australia, and Tasmania during Cambro-Ordovician times (modified after Foden et al., 2006); (B) tectonic sketch map showing the different structural zones of Northern Victoria Land (Antarctica), Tasmania, and southeast Australia (after Fl6ttmann et al., 1993, Foden et al., 2006); (C) geological map of western Tasmania (modified after Meffre et al., 2000).
Fig. 2. Geological sketch map of the Collingwood River-Lyell Highway area of the Franklin Metamorphic Complex showing sample locations. A-B: Location of the geological sectio Map adapted from (Brown et al., 2005). (Crawford & Berry, 1992; Foster et al., 2005; Foden et al., 2006). The collision generated a Tethyan-style ophiolite complex containing abundant mafic-ultramafic rocks including boninities. High-pressure metamorphic rocks in this complex formed from fragments of the continental margin (Berry and Crawford, 1988; Crawford and Berry, 1992; Turner et al., 1998; Meffre et al., 2000; Foster et al., 2005). This Cambrian passive margin consists of continental-derived turbidite intercalated with basalt and intruded by dolerite dykes and sills, and it overlies early Neoproterozoic shallow-water sedimentary rocks (Fig. 2C; Meffre et al., 2000). The passive margin of Tasmania was involved in a collision with an island arc system at the beginning of the convergent stage of the Delamerian-Tyennan-Ross Orogeny (520 to 505 Ma)
Fig. 2. Geological sketch map of the Collingwood River-Lyell Highway area of the Franklin Metamorphic Complex showing sample locations. A-B: Location of the geological sectio Map adapted from (Brown et al., 2005). (Crawford & Berry, 1992; Foster et al., 2005; Foden et al., 2006). The collision generated a Tethyan-style ophiolite complex containing abundant mafic-ultramafic rocks including boninities. High-pressure metamorphic rocks in this complex formed from fragments of the continental margin (Berry and Crawford, 1988; Crawford and Berry, 1992; Turner et al., 1998; Meffre et al., 2000; Foster et al., 2005). This Cambrian passive margin consists of continental-derived turbidite intercalated with basalt and intruded by dolerite dykes and sills, and it overlies early Neoproterozoic shallow-water sedimentary rocks (Fig. 2C; Meffre et al., 2000). The passive margin of Tasmania was involved in a collision with an island arc system at the beginning of the convergent stage of the Delamerian-Tyennan-Ross Orogeny (520 to 505 Ma)
Representative garnet analyses for eclogite r: rim; m: mantle; c: core; Fe** calculated after Ryburn et al. (1976).
Representative garnet analyses for eclogite r: rim; m: mantle; c: core; Fe** calculated after Ryburn et al. (1976).
r: rim; c: core; sy: symplectite; Fe** calculated after Ryburn et al. (1976). Representative pyroxene analyses for eclogite
r: rim; c: core; sy: symplectite; Fe** calculated after Ryburn et al. (1976). Representative pyroxene analyses for eclogite
sy: symplectite; kel: kelyphite; porphyr: porphyroblastic; cleav: cleavage; Fe>* calculated after Holland and Blundy (1994). Representative amphibole analyses for eclogite Table 3
sy: symplectite; kel: kelyphite; porphyr: porphyroblastic; cleav: cleavage; Fe>* calculated after Holland and Blundy (1994). Representative amphibole analyses for eclogite Table 3
Representative garnet, white mica, biotite, plagioclase and tourmaline analyses for host pelitic schist Table 5
Representative garnet, white mica, biotite, plagioclase and tourmaline analyses for host pelitic schist Table 5
sy: symplectite. Representative white mica, biotite, plagioclase and epidote analyses for eclogite
sy: symplectite. Representative white mica, biotite, plagioclase and epidote analyses for eclogite
Fig. 4. Garnet ternary diagram after Coleman et al. (1965). Plotted data refer to garnets from the Collingwood River eclogite samples. Garnet compositions from Northern Victoria Land (Antarctica) (Di Vincenzo et al., 1997) are shown for comparison (grey area). End members are almandine + spessartine (Alm+Sps), grossular (Grs), and pyrope (Prp). Fields A, B, and C represent the compositional variations of garnets in eclogites associated with kimberlites and peridotites (A), gneiss (B), and blueschist (C). Garnets from Antarctica partly overlap with those of Tasmania. However, the core compositions of garnet from Tasmania lie in the C field, whereas the rims are mainly in the B field. The opposite is reported for garnets from Antarctica.
Fig. 4. Garnet ternary diagram after Coleman et al. (1965). Plotted data refer to garnets from the Collingwood River eclogite samples. Garnet compositions from Northern Victoria Land (Antarctica) (Di Vincenzo et al., 1997) are shown for comparison (grey area). End members are almandine + spessartine (Alm+Sps), grossular (Grs), and pyrope (Prp). Fields A, B, and C represent the compositional variations of garnets in eclogites associated with kimberlites and peridotites (A), gneiss (B), and blueschist (C). Garnets from Antarctica partly overlap with those of Tasmania. However, the core compositions of garnet from Tasmania lie in the C field, whereas the rims are mainly in the B field. The opposite is reported for garnets from Antarctica.
Fig. 5. Chemical zonation of different types of garnet in terms of the almandine (100*Xre), pyrope (100*Xyg), grossular (100*Xc,), and spessartine (100Xn) end members. Note the different profiles for pyrope, grossular, and spessartine in the different microtextural occurrences of garnet. Profile (A) refers to large porphyroblastic garnet, profile (B) refers to small recrystallized garnet, and profile (C) refers to relics in mylonitized portions of the rock. For comparison, in Figs. 4, 6, and 7 the mineral composition of arnet, omphacite, and amphibole of eclogites from the Lanterman
Fig. 5. Chemical zonation of different types of garnet in terms of the almandine (100*Xre), pyrope (100*Xyg), grossular (100*Xc,), and spessartine (100Xn) end members. Note the different profiles for pyrope, grossular, and spessartine in the different microtextural occurrences of garnet. Profile (A) refers to large porphyroblastic garnet, profile (B) refers to small recrystallized garnet, and profile (C) refers to relics in mylonitized portions of the rock. For comparison, in Figs. 4, 6, and 7 the mineral composition of arnet, omphacite, and amphibole of eclogites from the Lanterman
Fig. 6. Pyroxene composition diagram (Essene and Fyfe, 1967). Plotted data are pyroxene from the Collingwood River eclogite samples and from Northern Victoria Land (Antarctica) (Di Vincenzo et al., 1997). Omphacites from Antarctica are more jadeite rich than those from Tasmania. Representative points in the sodic augite field refer to clinopyroxene in the symplectite after omphacite.
Fig. 6. Pyroxene composition diagram (Essene and Fyfe, 1967). Plotted data are pyroxene from the Collingwood River eclogite samples and from Northern Victoria Land (Antarctica) (Di Vincenzo et al., 1997). Omphacites from Antarctica are more jadeite rich than those from Tasmania. Representative points in the sodic augite field refer to clinopyroxene in the symplectite after omphacite.
Fig. 7. Variation in composition of amphibole in terms of 100xNa/(Na+Ca) versus 100 Al/(A+Si). Plotted data are amphiboles from the Collingwood River eclogite samples (squares) and grey areas refer to Northern Victoria Land (Antartica) (Di Vincenzo and Palmeri, 2001). Compositional fields of amphiboles from different metamorphic series are from (Laird and Albee, 1981).
Fig. 7. Variation in composition of amphibole in terms of 100xNa/(Na+Ca) versus 100 Al/(A+Si). Plotted data are amphiboles from the Collingwood River eclogite samples (squares) and grey areas refer to Northern Victoria Land (Antartica) (Di Vincenzo and Palmeri, 2001). Compositional fields of amphiboles from different metamorphic series are from (Laird and Albee, 1981).
Fig. 8. Photomicrographs of microstructures from hosting schists, Collingwood River (Tasmania). Mineral symbols after Kretz (1983). (A) Porphyroblastic garnet with inclusion: wrapped around by the dominant foliation defined by muscovite and biotite. One nicol, sample RC0620. (B) Small garnets together with biotite and muscovite along the dominan foliation. One nicol, sample RO227. (C) Kyanite relics within large flakes of secondary muscovite. One nicol, sample RO227. (D) Fibrolitic sillimanite at the contact between plagioclas¢ and quartz. Muscovite and garnet are also present. One nicol, sample RO227.
Fig. 8. Photomicrographs of microstructures from hosting schists, Collingwood River (Tasmania). Mineral symbols after Kretz (1983). (A) Porphyroblastic garnet with inclusion: wrapped around by the dominant foliation defined by muscovite and biotite. One nicol, sample RC0620. (B) Small garnets together with biotite and muscovite along the dominan foliation. One nicol, sample RO227. (C) Kyanite relics within large flakes of secondary muscovite. One nicol, sample RO227. (D) Fibrolitic sillimanite at the contact between plagioclas¢ and quartz. Muscovite and garnet are also present. One nicol, sample RO227.
Fig. 9. Chemical zonation of garnets from pelitic schist hosting the eclogite from the Collingwood River in terms of the almandine (100 X;-) pyrope (100* Xm), grossular (100* Xca) and spessartine (100 Xmn) end members.
Fig. 9. Chemical zonation of garnets from pelitic schist hosting the eclogite from the Collingwood River in terms of the almandine (100 X;-) pyrope (100* Xm), grossular (100* Xca) and spessartine (100 Xmn) end members.
Fig. 10. Prograde (dashed grey arrow) and retrograde P-T path (thick black arrow) for the eclogite from the Collingwood River (Tasmania). Question mark (?) refers to th unconstrained stage I. Coesite-quartz curve after Bohlen and Boettcher (1982); Ab=Jd+Qtz and jadeite isopleth (Jd39) are after Holland (1983). Dit Ms=Grs+Prp+Cel is after Water and Martin (1993); Chl+Pl+Qtz=Hbl+Zo+CO2+V and Al tot content of hornblende are after Plyusnina (1982); aluminium silicate triple-point is according to Holdaway (1971) isopleths of Si** content are after Massonne and Schreyer (1987); and barroisite and actinolite stability field are after Ernst (1979). Greenschist-facies (GS) and amphibolite-facie (AM) fields are after Spear (1993). P-T boxes are based on thermobarometric estimates, and mineral symbols are according to Kretz (1983); Phe is phengite, Cel is celadonite, and Ba i barroisite.
Fig. 10. Prograde (dashed grey arrow) and retrograde P-T path (thick black arrow) for the eclogite from the Collingwood River (Tasmania). Question mark (?) refers to th unconstrained stage I. Coesite-quartz curve after Bohlen and Boettcher (1982); Ab=Jd+Qtz and jadeite isopleth (Jd39) are after Holland (1983). Dit Ms=Grs+Prp+Cel is after Water and Martin (1993); Chl+Pl+Qtz=Hbl+Zo+CO2+V and Al tot content of hornblende are after Plyusnina (1982); aluminium silicate triple-point is according to Holdaway (1971) isopleths of Si** content are after Massonne and Schreyer (1987); and barroisite and actinolite stability field are after Ernst (1979). Greenschist-facies (GS) and amphibolite-facie (AM) fields are after Spear (1993). P-T boxes are based on thermobarometric estimates, and mineral symbols are according to Kretz (1983); Phe is phengite, Cel is celadonite, and Ba i barroisite.
Reported estimates represent the average + standard deviation (20) of values (n> 1) using different couples. Values for n=1 refer to a single couple. n: number of couples used for calculation. Calibrations: EG: Ellis and Green (1979); K: Krogh (1988); Ai: Ai (1994); P: Powell (1985); R: Ravna (2000); GP: Graham and Powell (1984); Pe: Perchuck et al. (1985); Ply: Plyusnina (1982); HB: Holland and Blundy (1994); CF: Colopietro and Friberg (1987); GS: Ganguly and Saxena (1984); PL: Perchuck and Lavrent'eva (1983); KR: Kleemann and Reinhardt (1994). T and P estimates for the eclogites (RO380 and RC0611) and host pelitic schist (227) Table 6
Reported estimates represent the average + standard deviation (20) of values (n> 1) using different couples. Values for n=1 refer to a single couple. n: number of couples used for calculation. Calibrations: EG: Ellis and Green (1979); K: Krogh (1988); Ai: Ai (1994); P: Powell (1985); R: Ravna (2000); GP: Graham and Powell (1984); Pe: Perchuck et al. (1985); Ply: Plyusnina (1982); HB: Holland and Blundy (1994); CF: Colopietro and Friberg (1987); GS: Ganguly and Saxena (1984); PL: Perchuck and Lavrent'eva (1983); KR: Kleemann and Reinhardt (1994). T and P estimates for the eclogites (RO380 and RC0611) and host pelitic schist (227) Table 6
Fig. 11. Comparison of the prograde and retrograde paths of eclogites from Tasmania (grey arrows) and Northern Victoria Land (Antarctica) (black arrows). Reaction curves and grey P-T boxes as in Fig. 10. P-T boxes and the P-T-t path from Antarctica are from Palmeri et al. (2003; 2007).
Fig. 11. Comparison of the prograde and retrograde paths of eclogites from Tasmania (grey arrows) and Northern Victoria Land (Antarctica) (black arrows). Reaction curves and grey P-T boxes as in Fig. 10. P-T boxes and the P-T-t path from Antarctica are from Palmeri et al. (2003; 2007).
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Metamorphic PetrologyPetrology and GeochemistryGondwana Research
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