Baddeleyite, Zirconolite and Calzirtite in Lateritic Rocks from Ryoke and Chichibu Terranes, Japan

42 Journal of Mineralogical andD. NishioPetrological and T. Sciences, Minakawa Volume 99, page 42─53, 2004 Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 43

Baddeleyite, zirconolite and calzirtite in lateritic rocks from Ryoke and Chichibu Terranes, Japan

* * Daisuke NISHIO and Tetsuo MINAKAWA

*Institute of Biology and Earth Science, Petrology and Economic Geology, Graduate school of Science ─ And ─ Engineering, Ehime University, Bunkyo ─ cho 2 ─ 5, Matsuyama, Ehime 790 ─ 8577, Japan

Baddeleyite, zirconolite and calzirtite were found in lateritic rocks from Ryoke and Chichibu Terranes in southwestern Japan. This is a new type of natural occurrence of the minerals. The lateritic rocks are associ- ated with limestone widely distributed into Ryoke metamorphic and Chichibu non ─metamorphic complexes. Baddeleyite, zirconolite and calzirtite are associated with Ti minerals such as anatase, ilmenite, perovskite and titanite. Calzirtite occurs simultaneously with perovskite. Rhabdophane─(Ce) like minerals also occurs in the lateritic rocks such as in emeries from Ko ─Oge Island. Baddeleyite and calzirtite have compositions close to the

ideal compositions, ZrO2 and Ca2Zr5Ti2O16. Zirconolite, CaZrTi2O7, accommodates significant amounts of Fe, Nb, Ta, and small amounts of Al and REE. Minor amounts of ACT are also found in the mineral. The chemi- cal substitution in zirconolite is controlled by the reaction: REE3+ + 2(Al + Fe)3+ + (Nb + Ta)5+ ←→ Ca2+ + 3Ti4+. Baddeleyite is a relict of the lateritization stage, or formed by the decomposition of zircon. Zirconolite formed during the prograde stage of metamorphism by the reaction; calcite + 2anatase + baddeleyite ←→ zirconolite + ─ CO2. The formation of calzirtite in Ca metasomatic emery is independent from the deformation of zirconolite during the prograde stage of metamorphism.

Introduction rane. Zirconolite from the Shinkiura mine was found in the metamorphic laterite as emery, belong to the Chichibu The sedimentary and metamorphic rocks related to Terrane. Calzirtite found in the lateritic metamorphic rock laterite occur in the Ryoke and Chichibu Terranes of from Ko─Oge Island, are part of the Ryoke Terrane. Japan (Iwao, 1978; Nishio and Minakawa, 2003). The Although zirconolite occurs in a wide range of rock major minerals in the host lateritic rock were described types and parageneses, the majority come from carbon- (e.g. Shimazaki et al., 1984; Nishio and Minakawa, 2003; atites (e.g. Williams and Gieré, 1996). Occurrences of Nishio et al., 2003), but the Zr ─bearing mineral was not. this mineral from laterite and related rocks have not yet The Zr minerals generally occur as accessory phases in been reported. Baddeleyite and calzirtite were not found the host rock. These Zr minerals usually contain REE in lateritic rocks, either. (rare earth elements including Y) and ACT (actinide In this paper we intend to report on newly discov- element). Therefore, the behavior of Zr minerals in a ered natural occurrences. We will also describe the crys- rock also controls the behavior of minor elements such tal chemistry of baddeleyite, zirconolite and calzirtite as REE and ACT. We discovered three Zr minerals, from the Ryoke and Chichibu Terranes in southwestern baddeleyite, zirconolite and calzirtite, from the Ryoke Japan. and Chichibu Terranes of Japan. Baddeleyite found in lateritic metamorphic rocks from Yuge, Ko ─ Oge and Mu- Interpretation of zirconolite and calzirtite tsuki Islands, belongs to the Ryoke Terrane. The lateritic sedimentary rocks from Kuwao, where baddeleyite was Zirconolite and calzirtite, together with their polytypes, found, belong to the Chichibu Terrane. Zirconolite found have compositions nearly equivalent to CaZrTi2O7 and ─ in the metamorphic laterite of Yuge, Myojin, Ko Oge and Ca2Zr5Ti2O16, respectively. In this study, the names of Mutsuki Islands, are from the metamorphic Ryoke Ter- zirconolite and calzirtite are used here as group names. D. Nishio, d─[email protected]─u.ac.jp Corresponding author The nomenclatures of zirconolite and calzirtite are de- T. Minakawa, [email protected]─u.ac.jp fined as follows. 42 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 43

only by single ─ crystal X ─ ray diffraction, because the Zirconolite two polytypes change in a continuous manner in small domains. Calzirtite ─ 1O transforms into another polytype Zirconolite is metamict or non ─ metamict mineral with tetragonal symmetry (calzirtite ─ 1Q) after heating to with many polytypes: zirconolite ─ 2M is a two layered 700 ─ 1350°C (Callegari et al., 1997). monoclinic polytype, zirconolite ─3O is a three layered orthorhombic polytype, zirconolite─3T is a three layered Geological setting

trigonal polytype of CaZrTi2O7 (Bayliss et al., 1989).

Zirkelite is a cubic mineral with (Ti, Ca, Zr)O2－x, and Figure 1 shows the location and geological map of polymignite is metamict zirconolite (Bayliss et al., the region studied in this paper. The Geiyo Islands are 1989). Smith and Lumpkin (1993) and Coelho et al. located in the central area of the Seto Inland Sea. From (1997) described synthetic 4M and 6T phases related to east to west, Yuge, Myojin, Ko ─ Oge and Mutsuki Islands zirconolite, which appear to be supercells of the zircono- are included in Ehime Prefecture. Cretaceous plutonic lite ─ 2M and 3T structures, respectively. rocks are widely distributed in the Geiyo Islands, and are considered to be part of the Ryoke Terrane (Suyari Calzirtite et al., 1992). The Islands of Yuge, Myojin, Ko ─ Oge and Mutsuki are mainly composed of schistose and massive Two polytypes of calzirtite have been reported: cal- granite or granodiorite, gneiss, schistose hornfels and zirtite ─ 1Q is a tetragonal polytype, and calzirtite ─1O is plagioclase ─amphibole schists. Limestone is included

an orthorhombic polytype of Ca2Zr5Ti2O16 (e.g., Rossell, in gneisses, crystalline schist or schistose hornfels (e.g. 1982; Sinclair et al., 1986; Callegari et al., 1997). The Miyahisa et al., 1980; Shimazaki et al., 1984; Matsuura, tetragonal and orthorhombic forms are distinguishable 2000; Seno and Matsuura, 2000; Nishio and Minakawa,

Figure 1. Location and geological map of Yuge, Myojin, Ko─Oge and Mutsuki Islands from Ryoke Terrane and Kuwao and the Shinkiura mine from Chichibu Terrane, Japan. 44 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 45

Figure 2. Backscattered electron image of baddeleyite, zirconolite and calzirtite and the rhabdophane ─(Ce) like mineral from the Ryoke Terrane and Chichibu Terrane, Japan. A: from Yuge Island, B: in Ca─added zone from Ko─Oge Island, C: from Kuwao, D: from Shinkiura mine, E: in non─metasomatic zone from Ko─Oge Island. All, allanite─(Ce); An, anatase; Ap, apatite; Bd, baddeleyite; Clz, calzirtite; Ilm, ilmenite; Mgt, magnetite; Rha, rhabdophane─(Ce) like mineral; Sc, scheelite; Zir, zirconolite.

2003; Nishio et al., 2003). Ohita Prefecture (e.g. Iwao, 1978; Suyari et al., 1992). Mesozoic and Paleozoic strata distributed in the south of Shikoku and Kyushu and are grouped in the Chi- Occurrence and paragenesis chibu Terrane (e.g. Karakida et al., 1992). The group in Shikoku and Kyushu are composed mainly of pelitic rock, Zr minerals are found in lateritic rocks included in chert and limestone (e.g. Yoshimura et al., 1962; Suyari limestone from the Ryoke and Chichibu Terranes. The et al., 1992). Limestone from Kuwao, Kochi Prefecture rocks are characterized by high Al, Fe and Ti and low Si is non ─metamorphosed, although it has suffered slight content. Localities where baddeleyite, zirconolite and alteration and skarn formation through contact with the calzirtite were found are summarized in Table 1. The oc- Ohkueyama granite intrusion from the Shinkiura mine, currences and paragenesis of baddeleyite, zirconolite and 44 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 45

Figure 3. Photomicrographs of zirconolite and calzirtite from Yuge Island and Ko─Oge Island from the Ryoke Terrane, Japan. A and B from Yuge Island; C, D, E, and F from Ko─Oge Island. Bars are 30um long. A, C, and E: Plane─polarized light, B, D, and F: Crossed polars. Bd, baddeleyite; Clz, calzirtite; Pv, perovskite; Zir, zirconolite.

Table 1. List of occurrences of baddeleyite, zirconolite and calzirtite in the lateritic rock from Ryoke Terrane and Chichibu Terrane, Japan

+, obserbed; −, not obserbed. 46 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 47

Table 2. Chemical compositions of Zr minerals from the Ryoke Terrane, Japan

* total Fe as Fe2O3. Bd, baddeleyite; Clz, calzirtite; Zir, zirconolite; Zr, zircon. Zir(L) and (H) are Low and High Zir in Figure 2B, respectively. calzirtite are described as follows. on Yuge, Myojin and Mutsuki Islands. The composition of the lateritic rocks from Ko ─Oge Island is consistent Ryoke Terrane with emery (Nishio et al., 2003). Emery in the region is classified in two zones, one as a non ─metasomatic zone, Recrystallized lateritic rocks with dark color are included and another as a metasomatically Ca─added zone (Nishio in limestone from Yuge, Myojin, Ko─Oge and Mutsuki Is- et al., 2003). Calzirtite is only found in the latter. The lands. The lateritic rocks from these islands show a little constituent minerals of the lateritic rock from each island difference in the main constituent minerals from each show a granoblastic texture. other. They are composed of potassic ─magnesiosadana- Baddeleyites from Yuge, Ko ─Oge and Mutsuki Is- gaite, vesuvianite, hercynite and ilmenite on Yuge Island; lands are usually too fine to observe under a microscope, titanian esseneitic diopside, potassic ─magnesiosadana- and are often exclusively accompanied with ilmenite gaite, hercynite and ilmenite are the main constituents and small amounts of scheelite (Fig. 2). However bad- on Myojin Island; and an assemblage of Al ─Fe ─Ti rich deleyite from Yuge Island shows a semi ─euhedral form diopside, potassic ─magnesiosadanagaite, hercynite and about 30 μm in diameter in rare cases (Fig. 3). In Ko ─ ilmenite form the rocks on Mutsuki Island (Shimazaki et Oge Island, zirconolite forms anhedral grains of about al., 1984; Nishio and Minakawa, 2003). The presence 100 μm in maximum length and is associated with il- of a very small amount of perovskite has been confirmed menite, perovskite and anatase. It is often intergrown 46 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 47

with calzirtite in the Ca ─added zone of emery (Fig. 2). Table 3. Chemical compositions of Zr minerals from the Zirconolite on Ko ─Oge Island also shows compositional Chichibu Terrane, Japan zoning accompanied with a mineral composed of Ti, Ca, U, and W as the main constituents (Fig. 2). Zirconolite associated with ilmenite or titanite also occurs on Yuge, Myojin and Mutsuki Islands (Table 1). The fractography of zirconolite from the Ryoke Terrane revealed non─cubic symmetry. Calzirtite often exists as anhedral intergrown crystal with 2 ─10 μ m in length in zirconolite associ- ated with perovskite and anatase (Fig. 2). Baddeleyite, zirconolite and calzirtite appear with colorless, orange ─ brown and light ─yellow under an openpolar mode under a microscope, and high order interference color under crossed polars (Fig. 3). A small amount of zircon is also found in the lateritic rocks of these islands. From Ko ─ Oge Island, the presence of a small amount of a cerium phosphate mineral was recognized without any relation to metasomatism. It is closely associated with apatite and allanite─(Ce) (Fig. 2).

Chichibu Terrane

From Kuwao, Kochi Prefecture, and the Shinkiura mine, Oita Prefecture, Zr minerals occur in lateritic rocks as well. The rocks, emery, from the latter region where re- ported for the first time in Japan (Yoshimura et al., 1962). The lateritic rock from Kuwao is sedimentary, and formed during the diagenesis. It shows a pisolitic texture. In the Shinkiura mine, the pisolitic texture was also observed in rocks (Iwao, 1972). Limestone from Kuwao includes a dark colored lat- eritic rock composed of diaspore, berthierine and anatase as main constituent minerals. We confirmed the pres- ence of baddeleyite and zircon associated with anatase in this rock (Fig. 2). These Zr minerals are only a few μm

in size, and therefore it is difficult to observe under a * total Fe as Fe2O3. microscope. The lateritic rock in the Shinkiura mine, cor- Bd, baddeleyite; Zir, zirconolite; Zr, zircon. Zir(L) and (H) responding to emery, is composed of corundum, hercynite are Low and High Zir in Figure 2D, respectively. and magnetite as main constituents, with ilmenite, mar- garite and diaspore as accessory minerals. The Zr mineral in emery from the Shinkiura mine is a 10 μm anhedral chemical composition of the cerium phosphate mineral zirconolite associated with ilmenite, showing variety and related minerals from Ko─Oge Island are given in Ta- compositional zoning (Fig. 3). ble 4. ACT such as Th and U are generally not included in Zr minerals. Although zirconolite is known to occur Crystal chemistry in the metamict state (e.g. Williams and Gieré, 1996), the lower ACT in zirconolite from the lateritic rock suggests The chemical compositions of the minerals were deter- it to be non─metamict. mined using a JOEL JSM─5400 (EDS). The ZAF method was used for the conversion and correction of observed Ryoke Terrane data to real composition. The chemical composition of baddeleyite, zirconolite and calzirtite from the Ryoke Baddeleyites from Yuge, Ko─Oge and Mutsuki Islands ac- and Chichibu Terranes, are shown in Tables 2 and 3. The commodate small amounts of Ti, Fe, and Hf. Zirconolite 48 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 49

Table 4. Chemical compositions of rhabdophane─(Ce) like mineral and related minerals from Ko─Oge Island

* total Fe as FeO. ** calculation. All, allanite─(Ce); Ap, apatite; Rha, rhabdophane─(Ce) like mineral.

from Ko─Oge Island generally accommodates significant The chemical composition of the cerium phosphate amounts of Fe, Nb, and Ta. The variation of these con- mineral corresponds to the ideal composition of rhabdo- ─ stituents causes a zoning. Zirconolites from Yuge and phane (Ce), if the deficit total wt.% considered to be 2H O Mutsuki Islands contain a small amount of Y. Calzirtite (Table 4). Although the rhabdopane ─(Ce) like mineral has an almost ideal composition, Ca2Zr5Ti2O16. In spite shows little compositional variation, Ce is always superior of their wide variation of compositions, zircons from to La, Nd and any other REE. individual islands contain very small amounts of REE and ACT. In Ko─Oge Island, a mineral composed of Ti, Chichibu Terrane Ca, U, and W was found in association with zirconolite. It has not yet been identified because of its minuteness Baddeleyite from Kuwao generally contains significant and small amounts. The details of this mineral will be amount of Ti and small amounts of Ca and Hf. Zircono- reported in the future. lite from the Shinkiura mine generally contains significant 48 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 49

Figure 4. Chemical variation in zirconolite from Yuge Island, Myojin Island, Ko ─Oge Island, Mutsuki Island and Shinkiura mine from the Ryoke Terrane and Chichibu Terrane of southwest Japan. 50 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 51 amounts of Fe, Nb and Ta. Especially “High ─Zr” in Calzirtite shows significantly less compositional Figure 2D accommodates large amounts Y and small variation than zirconolite, in spite of these two minerals amounts of other REE. possessing identical major elements (Ca, Zr and Ti) and having been subjected to similar paragenetic conditions. Discussion Calzirtites intergrown in zirconolite have been reported from Jacupiranga, Brazil (Bellatreccia et al., 1999) and Chemical substitutions in zirconolite and calzirtite Schryburt, Canada (Williams and Platte, 1993). Minor substitutions of Nb and Ta for Ti are observed in carbon- Zirconolite has five cation sites that can accommodate atite. Calzirtite from Ko ─Oge Island, however, shows elements with varieties in valency and size of ion (e.g. only minor substitution of Fe3+ for Ti. The substitutions Ringwood, 1985; Williams and Gieré, 1996): Ca in 8 ─ of Hf for Zr and Nb for Ta are hardly observed in compar- coordination (M8 site), Zr in 7 ─coordination (M7 site), ison to some other occurrences. The occupancy of Fe3+ and Ti in three distinct sites, 6 ─coordination (M6 site), in the Ti sites in calzirtite from Ko ─Oge Island is about and a pair of 5─coordination (M5 sites) (e.g. Gieré et al., 1─3% in atomic ratio. 1998). In natural zirconolites and synthetic equivalents, the chemical variation is extensive and thirty or more ele- Origin of Zr minerals ments may be accommodated at the concentration level ranging from 0.1 to 1.0 wt.% (e.g. Williams and Gieré, Baddeleyite, zirconolite and calzirtite from the Ryoke and 1996; Gieré et al., 1998). Therefore, the study of zircono- Chichibu Terranes, occur in the lateritic rock, which has lite has been important in the field of radioactive waste undergone contact metamorphism, but without metasoma- management (e.g. Malmström, 2000). The predominant tism caused by the granitic or related plutonic intrusions. substitutions are REE and ACT for Ca; Hf for Zr; and Nb, These occurrences have been classified as a recrystallized Ta, W, Fe, and Mg for Ti (Gieré et al., 1998). A classifi- skarn. The emery lateritic rock from Ko ─Oge Island cation was proposed for five hypothetical end─members shows two modes of occurrence; a recrystallized zone and deduced from the observations on natural and synthetic a Ca─metasomatic zone. The lateritic rock from Kuwao is 5+ 3+ 2+ samples; CaZrTi2O7, CaZrM M O7, ACTZrTiM O7, a non─metamorphic rock. These lateritic rocks are char- 3+ 5+ 2+ REEZrTiM O7, REEZrM M O7. An analysis of the zir- acterized by high Al, Ti and Fe and very low Si content, conolite from the lateritic rock of the Ryoke and Chichibu and show pisolitic texture composed of corundum, her- Terranes revealed that Ca2+ + Ti4+ have a negative correla- cynite or diaspore (e.g. Iwao, 1972; Nishio et al., 2003). tion with (REE + ACT) + Fe3+, and that the Ti4+ content These rocks correspond to metamorphic rock or sedi- also has a negative correlation with Fe3+ + (Nb + Ta)5+ as ment of laterite (e.g. Iwao, 1972; Nishio and Minakawa, shown in Figure 4. The substitution of ACT, however, is 2003; Nishio et al., 2003). Therefore, Zr is considered very little or negligible. No correlation was observed be- to be derived from the laterite as well. The existence of tween Al and Fe3+ as M3+ (Fig. 4). Therefore, the incorpo- baddeleyite from Kuwao indicates that the mineral is a ration of relatively large amounts of Fe into zirconolite is relict of the lateritization stage because it is compara- 3+ 3+ 2+ 4+ 3+ expressed by reactions REE + M ←→ Ca + Ti and M tively stable under general diagenesis conditions (e.g. 5+ 4+ + (Nb + Ta) ←→ 2Ti with corresponding end members, Malmström, 2000). Moreover, the occurrence of rhabdo- 3+ 5+ 3+ REEZrTiM O7 and CaZrM M O7, respectively. Thus, phane─(Ce) like mineral in the emery from Ko─Oge Island 3+ it is concluded that the main substitution scheme of REE may indicate the reaction between allanite─(Ce) and relicts 3+ 5+ 2+ 4+ + 2(Al + Fe) + (Nb + Ta) ←→ Ca + 3Ti . of lateritization and apatite. Therefore, the ratio of REE The M7 site of zirconolite from the present region in both the rhabdophane ─(Ce) like mineral and allanite ─ of study is fully occupied by Zr together with a minor (Ce) is similar. amount of Hf. The present analytical results show a small excess of Zr + Hf in the M7 site (Fig. 4). In zirconolite, Formation of Zr minerals the elements in the M8 or Ti sites also show some deficits (Fig. 4). These observations suggest that the excess Zr Baddeleyite, zirconolite and calzirtite can plot in a simple ─ ─ ─ occupies the M8 site or one or more of the Ti sites, as quaternary system CaO TiO2 ZrO2 CO2 (Fig. 5), however previously mentioned (e.g. Williams and Gieré, 1996; the reaction between these minerals is limited (Gieré et Gieré et al., 1998). Zirconolites show no correlation be- al., 1998). The zirconolite and calzirtite forming reactions ─ ─ ─ tween Zr, Ca and Ti (Fig. 4). Consequently, the excessive in the CaO TiO2 ZrO2 CO2 system are shown in Table 5. elements in M7 site are probably evenly distributed in the The reaction between each Zr minerals applies to one of M8 and Ti sites. the reactions indicated in Table 5 as well. 50 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 51

a small amount of perovskite (Bd─Ca─An phase in Fig. 5). In Myojin Island and the Shinkiura mine, calcite, ilmenite and zirconolite with a small amount of perovskite or a large amount of titanite are found in the lateritic rocks (Ca ─An─Zir phase in Fig. 5). Ilmenite and titanite can plot the position of anatase and perovskite, respectively in Figure 5. In Kuwao, the lateritic non─metamorphic rock has an assemblage of baddeleyite, anatase and calcite (Bd─Ca ─ An phase in Fig. 5). The lateritic rock from Kuwao was considered to be source rock of the metamorphic later- itic rock from the region of the present study (Nishio and Minakawa, 2003). Therefore, the first reaction produced during the progressive metamorphism is considered by the reaction of baddeleyite + calcite + 2anatase ←→ zir- conolite + CO2 (the equation 3 in Table 5). ─ ─ ─ Figure 5. Chemographic diagram for the system CaO ZrO2 TiO2 From Ko ─Oge Island, emery is divided as non ─ CO2. An, anatase; Bd, baddeleyite; Ca, calcite; Clz, calzirtite; Pv, perovskite; Zir, zirconolite. metasomatic zone by prograde metamorphism and meta- somatosed in the Ca─added zone by retrograde metamor- phism (Nishio et al., 2003). The Ca─added zone has the Kato and Matsubara (1991) considered that the ap- assemblage calcite, anatase, perovskite (Pv), zirconolite pearance of baddeleyite depends on the thermal reactions and calzirtite (Clz) (Ca ─An ─Clz phase in Fig. 5). From in dolomite at about 700°C in which a small amount of the observation of the disappearance of baddeleyite and zircon is resolved. Although the metamorphic tempera- perovskite with the appearance of calzirtite, we consid- ture is assumed to be less than 700°C on the Yuge, Ko ─ ered that the calzirtite forming reaction is as follows. Oge and Mutsuki Islands (e.g. Miyahisa et al., 1980; 5baddeleyite + 2perovskite (2calcite + 2anatase) ←→ cal- Shimazaki et al., 1984; Nishio and Minakawa, 2003), zirtite (+ 2CO2) (in the equation 9 or 10 in Table 5).

zircon is decomposed into baddeleyite and SiO2 at about From the observation of calzirtite intergrowths in ─ ─ ─ 500°C and 50MPa under a SiO2 poor condition with ex- zirconolite in the Ca metasomatic zone of Ko Oge Island,

istence of H2O (e.g. Malmström, 2000). These were the the order of deposition was estimated as calzirtite first and average conditions for metamorphism in the Ryoke Ter- zirconolite second. The forming reactions of secondary rane (e.g. Suyari et al., 1992). A direct relation between zirconolite are as follows: baddeleyite and zircon has not been observed, but the 3perovskite + 5anatase + calzirtite ←→ 5zirconolite possibility of the formation of baddeleyite by the reaction (in the equation 2 in Table 5) → remains. 3calcite + 8anatase + calzirtite ← 5zirconolite + 3CO2 ─ ─ In the non metasomatic zone of Ko Oge Island, (the equation 4 in Table 5) → where emery is present, we can observe an assemblage of calzirtite + 8perovskite + 5CO2 ← 5zirconolite + 5calcite baddeleyite (Bd), anatase (An) and zirconolite (Zir) (Bd─ (the equation 6 in Table 5) An─Zir phase in Fig. 5). In addition, on Yuge and Mutsu- Zirconolite that does not accompany calzirtite in the Ca ─ ki Islands, we can observe the presence of an assemblage metasomatic zone is a relict mineral formed by prograde of baddeleyite, calcite (Ca), ilmenite and zirconolite with metamorphism.

─ ─ ─ Table 5. List of zirconolite and calzirtite forming reactions in the system CaO ZrO2 TiO2 CO2 52 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 53

Although calzirtite was not observed in Yuge and References Mutsuki Islands, the examined mineral assemblages sug- gests the possibility that calzirtite may still be able to be Bayliss, P., Mazzi, F., Munno, R. and White, T.J. (1989) Mineral found in the future. nomenclature: zirconolite. Mineralogical Magazine, 53, 565 ─ 569. Bellatreccia, F., Della Ventura, G., Caprilli, E., Williams, C.T. and Conclusion Parodi, G.C. (1999) Crystal ─chemistry of zirconolite and calzirtite from Jacupiranga, São Paulo (Brazil). Mineral- (1) Baddeleyite, zirconolite and calzirtite are newly found ogical Magazine, 63, 649─660. as the first occurrences in the lateritic rocks from Ryoke Callegari, A., Mazzi, F. and Ungaretti, L. (1997) The crystal and Chichibu Terranes in Japan. These Zr minerals are structure of orthorhombic calzirtite of Val Malenco (Italy). Neues Jahrbuch für Mineralogie Monatshefte, 10, 467─480. associated with Ti minerals such as anatase, ilmenite, Coelho, A.A., Cheary, R.W. and Smith K.L. (1997) Analysis and perovskite and titanite in each region. Structural Determination of Nd ─substituted zirconolite ─4M. (2) Zirconolites from Ko ─Oge Island and the Shinkiura Journal of Solid State Chemistry, 129, 346─359. mine showed concentration zoning due to the composi- Gieré, R., Williams, C.T. and Lumpkin, G.R. (1998) Chemi- tional heterogeneity in Fe, Nb, Ta and a small amount cal characteristics of natural zirconolite. Schweizerische ─ of Y. Zirconolites from Ryoke and Chichibu Terranes Mineralogische und Petrographische Mitteilungun, 78, 433 459. ─ have a non metamict structure except cubic symmetry as Iwao, S. (1972) The remained laterite texture of emery from the zirkelite from the feature of chemistry and fractography. Shinkiura mine. Mining Geology, 22, 359─369 (in Japanese). (3) The solid solutions in zirconolite from the Ryoke Iwao, S. (1978) Re─interpretation of the chloritoid ─, staurolite ─, and Chichibu Terranes are expressed by the substitu- and emery─like rocks in Japan – chemical composition, oc- 3+ 3+ 2+ 4+ 3+ currence and genesis. Journal of the Geological Society of tions: REE + Fe ←→ Ca + Ti and Fe + (Nb + Japan, 84, 49─67. Ta)5+ → 2Ti4+. The overall main substitution is REE3+ ← Karakida, Y., Hayasaka, S. and Hase, Y. (1992) Regional Geology 3+ 5+ → 2+ 4+ + 2(Al + Fe) + (Nb + Ta) ← Ca + 3Ti . Calzirtite of Japan Part 9 KUSHU. pp. 371, Kyoritsu Shuppan CO., from Ko ─Oge Island has lower acceptability to incorpo- LTD. (in Japanese). rate Fe3+ than zirconolite. Kato, A. and Matsubara, S. (1991) Geikielite, baddeleyite and zir- (4) Baddeleyite is probably derived from laterite or conolite in dolomitic marble from the Neichi mine, Miyako formed by the resolution of zircon. We consider that City, Iwate Prefecture, Japan. Bulletin of the National Sci- ence Museum, Tokyo, Series. C, 17, 11─20. zirconolite was formed first during the prograde stage of Malmström, J.C. (2000) Zirconolite: Experiments on the Stability metamorphism by the reaction; calcite + 2anatase + in Hydrothermal Fluids. pp. 130, Beiträge zur Geologie der → baddeleyite ← zirconolite + CO2. The appearance of Schweiz, Geotechnische Serie Materiaux pour la Géologie de calzirtite in the Ca─metasomatic emery is not controlled by la Suisse, Série Géotechnique. the breaking down of zirconolite formed in the prograde Matsuura, H. (2000) Geology of the Mitsu district. With Geo- logical Sheet Map at 1:50,000, pp. 58, Geological Survey of stage of metamorphism. Japan (in Japanese with English abstract). (5) Zirconolite and calzirtite have individual polytypes. Miyahisa, M., Momoi, S., Minakawa, T., Noto, S. and Matsueda, Therefore, in the future, it is impossible to determine H. (1980) Fassaite from the Ryoke Metamorphic Rocks whether chemical composition and paragenesis influence of Shisaka ─jima, the Seto Inland Sea, Japan. Journal of its structural polytype in natural samples. Mineralogy Petrology and Economic Geology, 75, 25─29 (in Japanese with English abstract). Nishio, D. and Minakawa, T. (2003) The titanian esseneitic di- Acknowledgments opside in Al─skarn from Myojin and Mutsuki islands in Seto Inland Sea, Japan. Japanese Magazine of Mineralogical and The authors wish to thank Mr. T. Adachi (Nobeoka city) Petrological Sciences, 32, 68 ─79 (in Japanese with English abstract). and Mr. Y. Tamura (Ino ─cho) for acting as guides at the Nishio, D., Minakawa, T., and Noto, T. (2003) Emery from Shinkiura mine and Kuwao, respectively. We are deeply Ko ─Oge Island in Ryoke Terrane, Seto Inland Sea, Japan. indebted to Dr. T. Inoue and Dr. R. Hori of Ehime Uni- Japanese Magazine of Mineralogical and Petrological Sci- versity for the use of the analytical devices. We would ences, 32, 165─174 (in Japanese with English abstract). like to thank Dr. M. Bunno of Geological Museum in Ringwood, A.G. (1985) Disposal of high─level nuclear wastes: a ─ The Geological Survey of Japan for his help in analyzing geological perspective. Mineralogical Magazine, 49, 159 167. the data. The first author is grateful to Prof. T. Kawasaki Rossell, H.J. (1982) Calzirtite ─a fluorite ─related superstructure. and Dr. M. Sakakibara of Ehime University and Prof. K. Acta Crystallographica, B38, 593─595. Fujino of Hokkaido University for their discussion and Seno, M. and Matsuura, H. (2000) Late Miocene volcanic rocks encouragement. (Geiyo volcanic rock) and early ─middle Miocene volcanic rocks (Setouchi volcanic rocks) from the Geiyo Islands in the 52 D. Nishio and T. Minakawa Baddeleyite, zirconolite and calzirtite in lateritic rock from Ryoke and Chichibu Terranes 53

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