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Loveringite from the Last-Yavr Mafic-Ultramafic Intrusion, Kola Peninsula; a Second Occurrence in Russia

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Loveringite from the Last-Yavr Mafic-Ultramafic Intrusion, Kola Peninsula; a Second Occurrence in Russia Loveringite from the Last-Yavr mafic-ultramafic intrusion, Kola Peninsula; a second occurrence in Russia AND REW Yu. BA RKOV, YEVGENY E. SAVCHENKO, YURII P. MEN'SHIKOV & LARISSA P. BARKOVA Barkov, A. Yu., Savchenko, Ye. E., Men'shikov, Yu, P. & Barkova, L. P. : Loveringite from the Last-Yavr mafic-ultramafic intrusion, Kola Peninsula; a second occurrence in Russia. Norsk Geologisk Tidsskrift, Vol. 76, pp. 115-120. Oslo 1996. ISSN 0029- 196X. Loveringite, (Ca, REE)(Ti, Fe, Cr),1038 (a member of the crichtonite group) occurs in orthocumulates (plagioclase-bearing orthopyroxenites) of the Last-Yavr intrusion, which obviously represents a fragment of the Proterozoic Fedorova Tundra-Pana Tundra layered intrusion. The occurrence is situated immediately adjacent to the Archaean wall rocks at a lower structural leve! of the intrusion. The loveringite is closely associated with a typical intercumulus assemblage (phlogopite, quartz, albite-rich plagioclase, ilmenite, rutile and Ca-amphibole). Its composition is characterized by a relatively low con tent of REE and high concentrations of Cr and Mg. The rellectance values are in good agreement with published data; VHN 100= 912-1085. The unit-cell dimensions are a= 10.40 (3), c= 20.83 (6) Å. A. Yu. Barkov•, Ye. E. Savchenko, Yu. P. Men'sh ikov & L. P. Barkova, Geological In stitute, Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184200 Apatity, Russia. • Present address: Department of Geosciences and Astronomy, Un iversity of Oulu, FTN-90570 Oulu, Finland. Introduction between the hetter known Fedorova Tundra and Pana Tundra intrusions (Fig. l). The intrusions are located Loveringite, (Ca, REE)(Ti, Fe, Crb 038, a rare member between Archaean granitoids and the Palaeoproterozoic of the crichtonite group, was first described by Seidorechensky volcanogenic-sedimentary sequence. Fea- Gatehouse et al. ( 1978) from the Early Proterozoic Jim­ berlana layered intrusion, Australia. The mineral has also been discovered in the Bushveld layered complex, South Africa (Cameron 1978; 1979), and later in several Early Proterozoic mafic-ultramafic layered intrusions in Finland: Narankavaara, Penikat (A lapieti 1982; Alapieti & Lahtinen 1986) and Koitelainen (Tarkian & Mutanen 1987). Another Fennoscandian occurrence of members of the loveringite-davidite series was reported by Olerud ( 1988) from an Early Proterozoic albite felsite, Norway. Segalstad ( 1984) described an unusual Ti-rich oxide min­ cs;:]1 eral, the chemistry of which resembles that of the crich­ tonite group. Lorand et al. (19 87) reported an occurrence �2 of loveringite from the Early Palaeozoic Laouni complex, r::::::;]3 AJgeria. More recently, loveringite was identified in the �4 Burakovsky layered intrusion, Russian Karelia (Barkov t et al. 1994). Minerals of the loveringite-crichtonite series !S]s N have also been found in the Khibina alkaline complex, o 2 �6 '--L......J Kola Peninsula, Russia (Barkov et al., in prep.). KM In this paper we report a second Russian occurrence �7 of loveringite, from the Last-Yavr intrusion, Kola Peninsula. Fig . l. Simplified geological sketch-map of the contact area between the Fe­ dorova Tundra and Pana Tundra layered intrusions, showing location of the Last-Yavr intrusive body. Modified from Radchenko et al. (1980) l. Geological contacts; 2. Schists and mylonites after mafic and ultramafic rocks; 3. Archaean granitoids; 4. Palaeoproterozoic Seidorechensky complex of volcanic and sedi­ Brief geological description mentary rocks; 5. Faults; 6. Position of drill hole No. 72; 7. Mafic-ultramafic igneous rocks. Abbreviations used: Ff= Fedorova Tundra, PT= Pana Tundra, The Last-Yavr mafic-ultramafic intrusion is situated in LY = Last-Yavr intrusions. The inset shows the approximate location of the area the central part of the Kola Peninsula, at the contact on the Kola Peninsula. 116 A. Yu. Barkov et al. NORSK GEOLOGISK TIDSSKRIFT 76 (1996) Table I. Representative electron microprobe analyses (in wt.%) of minerals in loveringite-bearing pyroxenite fr om Last-Yavr. En Aug Pl Phi Am Ap Chr co re rim Si02 55. 17 52.99 59.06 60.30 40.41 48. 10 n.a. n.a. n.d. Ti02 0. 15 0.62 n.d. n.d. 2.63 0.40 n.a. n.a. 0.30 Al203 1.17 2.27 25.57 25.85 14.55 11.38 n.a. n.a. 9. 82 Cr203 0.33 0.64 n.d. n.d. 0.7 1 0. 10 n.a. n.a. 43. 18 V20, n.d. 0.04 n.d. n.d. 0.05 n.d. n.a. n.a. 0.74 Fe203 11.75 FeO 10.81 6. 18 0. 12 0. 10 5.89 7.7 1 0. 19 0.24 29.61 Mn O 0.27 0. 17 n.d. n.d. 0.04 0. 13 n.a. n.a. 0.45 MgO 30.70 18.65 n.d. n.d. 22.65 17.05 n.a. n.a. 1.32 CaO 1.14 17.32 7.10 7. 13 0.04 10.79 54.64 54.39 n.d. SrO n.a. n.a. n.a. n.a. n.a. n.a. 0. 11 n.d. n.a. Na20 0. 16 0.46 7.21 8.07 0.47 2. 10 n.a. n.a. n.a. K20 n.d. n.d. 0.03 O.o3 8.61 0. 10 n.a. n.a. n.a. Ce203 n.a. n.a. n.a. n.a. n.a. n.a. 0.21 0. 12 n.a. Ni O 0.09 0.05 n.a. n.a. 0. 13 0.06 n.a. n.a. n.d. ZnO n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 0.84 P20s n.a. n.a. n.a. n.a. n.a. n.a. 42.08 42.30 n.a. Cl n.a. n.a. n.a. n.a. n.d. 0.06 1.45 1.56 n.a. Cl-O 0.0 1 0.33 0.36 Total 99.99 99.39 99.09 101.48 96. 18 97.97 98.35 98.25 98.01 Number of cations 0= 8 0= 11 0= 23 0= 12.5 Si 1.94 1.94 2.65 2.65 2.85 6.80 Ti <0.01 0.02 0. 14 0.04 <0.01 Al 0.05 0. 10 1.35 1.34 1.21 1.90 0.42 Cr <0.0 1 0.02 0.04 0.0 1 1.24 V <0.01 <0.01 0.02 3+ Fe 0.06 <0.01 0.32 2 Fe + 0.26 0. 19 <0.01 <0.01 0.35 0.9 1 0.0 1 0.02 0.90 Mn <0.0 1 <0.01 <0.01 0.02 0.0 1 .. Mg 1.61 1.02 2.38 3.59 0.07 Ca 0.04 0.68 0.34 0.34 <0.01 1.63 4.95 4.92 Sr <0.01 Ce <0.01 <0.01 Na 0.0 1 0.03 0.63 0.69 O .o? 0.58 K <0.0 1 <0.01 0.77 Ni <0.01 <0.01 <0.01 <0.01 Zn 0.02 p 3.01 3.02 Cl 0.21 0.22 Abbreviatio ns: En= enstatite, Aug= augite, Pl= plagioclase, Phi= phlogopite, Am= amphibole, Ap= apatite, Chr= chromite (a euhedral grain enclosed within 3 enstatite). Total Fe as FeO; Fel+ in chromite was calculated assuming stoichiometry; Fe + in pyroxenes is from a program by Cebriå G6mez ( 1990). n.d. = not detected; n.a.= not analysed. tures of the regional geology shown in Fig. l strongly lished age determinations for the Last-Yavr body, but it suggest that the Last-Yavr intrusion represents a block may be considered to have a Proterozoic age, in common of the Fedorova Tundra-Pana Tundra intrusion, rather with the Fedorova Tundra, Pana Tundra and other than an individual layered intrusion. There are no pub- comparable layered intrusions in the Kola Peninsula, Russian Karelia and Finland. Table 2. Electron microprobe analyses (in wt.%) of ilmenite and rutile from Descriptions of the Last-Yavr geology were given by LastcYavr. Radchenko et al. ( 1980) and Bartenev et al. ( 1980, 1981). The geological information is based on drilling and limen ite Rutile geophysical work as the intrusion is wholly covered by l* 2* 3* 4** 5* 6* Quatemary deposits. The intrusion is a small body (ap­ 10 2 Ti02 53.77 52.81 53.72 52.61 97.86 98. 14 proximately km in surface area) that has undergone FeO 42.53 44.23 42.44 42.46 0. 16 0. 10 intensive regional deformation and was broken up by Cr203 n.d. n.d. n.d. n.d. 0.72 0.62 tectonic movements to form several blocks (Fig. 1). In Al203 n.d. n.d. n.d. n.d. 0.06 0.05 MgO 2.05 1.85 2. 18 2. 14 0.27 0. 16 general, the thickness of the intrusion increases towards Mn O 0.62 0.58 0.65 1.72 n.d. n.d. the Pana Tundra intrusion. The original cumulates are Total 98.97 99.47 98.99 98.93 99.07 99.07 either only locally preserved or completely altered, due to • Individual grains, •• a rim around loveringite. strong deformation and metamorphism, and relatively Total Fe as FeO. fresh rocks are present in subordinate amounts. The NORSK GEOLOGISK TIDSSKRIFT 76 (1996) Loveringite from the Kola Peninsula 117 A 8 er L.......J 10 pm Mn Ill ILO Ill l CH l Fig. 3. A: Sketch of a part of the loveringite grain shown in Fig. 2B ( drawn from a polished section). Note that loveringite (LO) is mantled by Mn-bearing ilmenite (IL), that is rimmed by chromite (CH).
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