Detrital Blue Sodic Amphibole in Recent Sediments, Southern Coast, Turkey
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J. geol. Soc. London, Vol. 138, 1981, pp. 83-92, 4 figs, 3 tables. Printed in Northern Ireland. Detrital blue sodic amphibole in Recent sediments, southern coast, Turkey M. A. Mange-Rajetzky SUMMARY:Detrital blue sodic amphibole, sporadiclawsonite and pumpellyiteoccur in beach and river sediments between Gazipasa and Manavgaton the southern Turkish coast. This area lies S of the metamorphic Alanya massif, which contributes to the detritus, but blueschists havenot previously been recorded in the region.The blue amphiboles have a provincial variation related to differing conditions during their formation. In the eastern region, in the vicinity of Gazipasaand Demirtas, homogeneous glaucophanes, sometimes with remnant Ca-amphiboles,are characteristic. In thewestern region the grainsexhibit a considerable variation of optical and physical properties and are crossitic-glaucophane, crossite and occasion- ally magnesio-riebeckite. Theefficacy of sedimentary mineralogy in reconstructing a hinterland is demonstrated. The geology of southern Turkey has attracted resear- Studies of the composite nappe system of the nearby chers for a number of years. Of particular interest is Antalya region by agroup of Frenchresearchers the region bordered by the towns Anamur, Beysehir, focussed particularly on the mode of origin and em- Isparta and Finike (Fig. l), where various nappe com- placement of the nappes of the‘Taurus occidental’ plexesindicate acomplicated geological structure. (Brunn1974; van derKaaden 1971; Monod et al. During the last 15 years several groups of geologists. 1974;Juteau 1975; Marcoux 1976;Dumont et al. applying the plate tectonic theory, have attempted to 1972; Delaune-Mayere et al. 1977 and Ricou et al. unravel its evolution in terms of a collision process. 1974, 1975, 1979). Detrital blue sodic amphibole, lawsonite and pum- Investigation of the modern sedimentsof the south- pellyite occur in river and coastal sediments between ern Turkish coast began in 1969, when a team from Gazipasa and Manavgat, supplied by riversdraining the Department of Geology,Imperial College, Lon- the metamorphic Alanya massif and its northern bor- don, in co-operation with M.T.A. (Turkish Geological derland.Blueschists indicate collision tectonics with Survey) started a comprehensive reconnaissance sur- conditions of high-pressuremetamorphism, and evi- vey of the area between Karatas and Antalya (Evans dence of their existence in the Alanya massif, where 1971).I joined the team in 1976 to investigate the they have not been recorded, has significant tectonic mineralogyand provenance of the river and coastal implications. sediments.During the course of thisanalysis blue The Alanya massif occupies the coastal range from sodic amphibole was encountered in beach and river theeastern side of Anamurto Alanya and extends sediments from around Gazipasa and as faras westward behindTertiary formations as far as the Manavgat. Manavgatriver. Thearea has not beenstudied in detail, but it is known that metamorphic rocks of the Mineralogy greenschist facies constructing the schistose group are overlain by marbles and dolomites (Blumenthal 1951; Ageneral study of beach and river sediments was Peyronnet 1971; Brunn et al. 1971; Brinkmann 1976). based on material separated from the 53 to 350 pm Locally metamorphosedbauxite alsooccurs in the sandrange. The coarser fractions are dominated by massif. Papersdescribing regional and stratigraphic lithic fragments, composite and ferruginous grain, and details include Arni (1939), Altini (1944), Blumenthal the best mineral assemblages were obtained from the (1951),Erentoz (1956), Peyronnet (1967, 1971), 53 to 212 pm range. The followingminerals were Brunn et al. (1971,1975), Argyriadis (1974) and identified: Ricou et al. (1974). Amphiboles: Blue sodic amphibole, blue-green hornblende; The northern flank of the Alanya massif as far as smallamounts of brownhornblende, tremolite-actinolite Kopriilii is in contact with the Palaeozoic-Mesozoic and grunerite. formations of the Hadim nappe which contain radio- F‘yroxenes:Augite which includesdiopsidic, acmitic and titaniferous varieties; diopside, diallage, enstatite, hypers- larites and ophiolites. From Kopriilii to the Manavgat thene. The pyroxenes usually occur in small amounts but valley units of the Antalya nappe outcropin a narrow, becomedominant, together with someolivine, W of complex zone between the Mesozoic formations of the Avsallar. Taurus Mountains and the limestones and marbles of Garnet and various micas show important local concentra- the Alanya massif. tions. 0016-7649/81/0100-0083$02.00 @ 1981 The Geological Society Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/138/1/83/4886977/gsjgs.138.1.0083.pdf by guest on 29 September 2021 84 M. A. Mange-Rajetzky LEGEND 0 25 %ll5 “km N Scak n t Metamorphic rocks of the Alanya massif Formations of Antalya nappe Mesozoic -Tertiary comprehensive series, main/y calcareous Massive peridotites Miocene Wasse Terfiary/Ouaternary “~ectonicwindow” with units of the Antalya and Hadirn nappe Lake lNnFX MAP BLACK SEA RC. 1. Schematic geological map showingthe structural units in the vicinity of the Alanya massif. After Brunn et al. (1973), Argyriadis (1974) and M.T.A. 1: 500,000 geological map of Turkey. Characteristic metamorphic minerals include kyanite, andalu- petrologicalprovince, characterized dominantly by site and chloritoid. metamorphic minerals. The epidote group is represented by clinozoisite; epidote is The minerals indicating high-pressurelrelatively low not common. temperature metamorphism include glaucophane and Accessories are abundantin the 53-63 @m fractionand other members of theglaucophane-riebeckite series, include tourmaline, zircon, apatite, rutile, sphene, lawso- nite and pumpellyite. together with sporadic lawsonite and pumpellyite. The Light fraction: Lithic fragments, micas and quartz make up abundance of blueamphiboles wasestimated by the mass of the sediments. The grains are often stained counts of 400-500 transparent minerals per sample, withiron-hydroxide. Radiolarian chert and fragments of but no attempt was madeto calculate the absolute volcanic matrix are common around Gazipasa and Manav- weight percentages of the individual mineral species, gat. Feldspars occur in minor quantities in all samples and since theabundant opaque minerals and composite are usually represented by sodic and intermediate plagio- grainswould have obscured theimportant ‘exotic’ clase. These grainsare poorly preserved. The sediments are mineral assemblages. Thepercentage data therefore rich in calcareous fragments, but during the preparation of indicate relative percentages (Table 1, Fig. 2). the samples for heavy mineral analysis these were removed by acid treatment. In a study of the mineralogy of the sediments of the Properties of the blue amphibole southernTurkish coast (Mange-Rajetzky 1979) the heavy mineraltechnique wasused and inferences Opticalanalyses weremade on the blueamphibole madeabout the petrography of thesource areas. from 4 samples containing large amounts of this min- Characteristicheavy mineral assemblages were dis- eral (Table 1). No attempt was made to determine the tinguished and their area1 distribution, in combination refractive indices because most of the coarser grains with light mineral data, enabled them to be mapped as showedslight encrustation or disintegration on the provinces, reflecting the petrographical nature of the surface. In the case of the finerclear and well pre- hinterland. servedgrains the small size made hand-picking and The present area constitutes part of a sedimentary observation difficult. Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/138/1/83/4886977/gsjgs.138.1.0083.pdf by guest on 29 September 2021 Detrital blue sodic amphibole, southern coast, Turkey 85 LEGEND I. , , , I ,, , . 2in 264 2l8212 k0 River samples 249 252278 257 258 265 271 239234214,204 221224 228 Coastal samples 240 226 FIG. 2. Generalizedgeological map showing sample locations and mineral units. After Argyriadis (1974) and M.T.A. 1:500,000 geological map of Turkey. Diagram below illustrates the distribution of blue sodic amphibole and associated minerals in the sediments. The grains in sample 224 from the vicinity of De- All grains have a very low birefringence displaying mirtasare generally (110) cleavageflakes andare pale-grey, blue or pale greyish-yellow interference characterizedby short prismatic habit. The pleo- colours. Most exhibit zoned or mottled extinction and chroism is well expressed: 8 brightlavender-blue, y this, as well asthe (110) orientation, limited the sky-blue. On a few thin specimens a,almost colourless measuring of themain extinctionangle; grains on to pale yellow, was observed by rolling the grains on (110) show almost parallel extinction.The interference the slide. figure is usually clear and visual inspection (using the Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/138/1/83/4886977/gsjgs.138.1.0083.pdf by guest on 29 September 2021 86 M. A. Mange-Rajetzky TABLE1: Percentages of blue sodic amphibole in some beach and river sediments Mouth of Mouth of Mouth of Manaugat Ir. Locality Sedre Cay Afara Cay Karpuz Irmagi Riuer sand Sample No, 224 257 252 281 Size grade (pm) 53-63 25.1 17.0 13.3 12.5 63-125 15.3 3.0 12.2 7.9 125-210 14.7 6.1 10.2 3.4 210-300 2.3 11.1 12.3 1.7 0 0 0 1.0 0 0 300-350 0 Percentage of total grains counted in 53-300 15.9 12.3 10.7 5.9 data in Phillips 1971, p. 145) showed a range of the 2V varying within a