Occurrence of rare borate minerals: Veatchite-A, tunellite, teruggite and cahnite in the Emet borate deposits, Turkey

Abstract

Abstract. The Emet borate deposits were formed in two separate basins, possibly part of an interconnected lacustrine playa lake, in areas of volcanic activity, fed partly by thermal springs and partly by surface streams. The borates are interlayered with tuff, clay and marl. Limestone occurs above and below the borate lenses. Sediments in both basins are similar but borate minerals show different mineralogical and geochemical features in the two basins.The Emet borate deposits are the only deposits known to contain any of the minerals veatchite-A, tunellite, teruggite and cahnite. Principal minerals are colemanite, with minor ulexite, hydroboracite and meyerhofferite.Thermal springs associated with local volcanic activity are thought to be the source of the borates. The initial brines from which the borates crystallized are deduced to have been high in sulphite and sulphate, low in chloride, and hence it is assumed that the initial brines were fed at all times by abundant calcium and boron with minor amounts of arsenic, strontium and sulphur. Realgar, celestite and native sulphur are almost ubiquitous in borates and sediments, and appear to have formed at all stages during deposition and diagenesis.The early colemanite, meyerhofferite, ulexite and teruggite nodules were probably formed directly from brines penecontemporaneously within the unconsolidated sediments below the sediment/water interface, and continued to grow as the sediments were compacted. Later generations of colemanite occur in vugs, veins and as fibrous margins to colemanite nodules. Tunellite appears to have formed during diagenesis with enrichment of Sr in some places. Diagenetic alterations include the partial replacement of colemanite by veatchite-A, cahnite, hydroboracite and calcite.

Bor Yataklarini İçeren Neojen Havzalarinin Jeoloji̇k Özelli̇kleri̇: Yataklarin Genel Değerlendi̇rmesi̇ Ve Gelecek Öngörüsü, Türki̇ye

“…Emet havzas› (Akdeniz ve Konak, 1979;Helvac›, 1984Helvac›, , 1986; flekil 3), bat›da Menderes Masifi metamorfik kayaçlar›na sokulum yapm›fl E¤rigöz granitoyidi ile do¤uda Afyon zonu metamorfik kayaçlar›n›n aras›nda yer al›r (fiekil 1 ve 2). Emet havzas›n›n stratigrafisi, bölgesel bir uyumsuzluk ile birbirinden ayr›-labilen iki Neojen volkanosedimanter birim içerir (fiekil 3).…”

“…Bu birimler, di¤er havzalardaki benzer kayaçlar ile yafl, litoloji ve deformasyon özellikleri aç›-s›ndan korele edilebilir ve Hac›bekir ve ‹nay Grubu olarak da adland›r›l›rlar. Dünya'n›n en büyük kolemanit ve probetit borat yata¤›, bu havzadaki ‹nay Grubunda bulunmaktad›r (Gawlik, 1956;Helvac›, 1984Helvac›, , 1986Helvac› ve Orti, 1998;Helvac› ve Alonso, 2000;Garcia vd., 2010).…”

“…Havza sedimanlar›-n›n B, S, Sr, As ve Li elementleri bak›m›ndan beslenmesini sa¤layan volkanizma, volkanik kayaçlar›n s›-cak meteorik sularla y›kanmas›, külün göl sedimanlar›n›n içine do¤rudan çökelimi veya magmadan gaz boflal›m› (degassing) süreçlerini kapsar. Yerel volkanik aktiviteye ba¤l› termal kaynaklar, borun muhtemel kayna¤› olarak düflünülmektedir (Helvac›, 1977;Helvac›, 1984;Helvac› ve Alonso, 2000).…”

“…Bafll›ca bor mineralleri kolemanit ve probertittir, bunun yan› s›ra az oranda üleksit, hidroborasit ve meyerhofferit bulunmaktad›r (fiekil 18). Emet borat yata¤›, viçit-A, tünellit, terrujit ve kahnit gibi nadir gözlenen baz› bor mineralleri içermektedir (Helvac› ve Firman, 1976;Helvac›, 1977;Helvac›, 1984;Helvac›, 1986;Helvac› ve Orti, 1998;Veigas vd., 2011). Do¤anlar sektöründeki arama kuyular›ndan al›nan örnekler üzerinde gerçeklefltirilen optik ve elektron mikroskop çal›flmalar›, karmafl›k bir mineral toplulu¤unun varl›¤›n› ortaya koymufltur.…”

The geochemistry of Boron-rich groundwater of the Karlovassi Basin, Samos Island, Greece

“…Celestite forms massive fine-grained aggregates, with numerous vugs filled with late stage formed euhedral prismatic celestite crystals. Spongy calcareous earthy material replaces the early formed borates near the surface [27] The presence of carbonate minerals as a weathering product developed on surface-exposed bodies of colemanite is a quite common phenomenon in borate deposits [38,39]. This conversion of colemanite to carbonate minerals is caused by intense weathering due to groundwater flow and carbonates often show pseudomorphism after colemanite [38].…”