Mineralogical-Petrographic characteristics of garnet porphyroblasts (Ekinözü-Kahramanmaraş), determination of metamorphism conditions and gemstone potential

Abstract

The studied garnet porphyroblasts occur within metamorphic rocks consisting of schists with variable mineralogical compositions in the Ekinözü (Kahramanmaraş) region. The porphyroblasts crystallized in pentagonal dodecahedron forms, ranging in size from 0.5 to 4 cm and exhibit dark red to reddish-black colors with vitreous luster. Microscopic observations reveal that the garnet porphyroblasts display a highly fractured and cracked texture, containing inclusions of quartz, chlorite and opaque minerals such as ilmenite-magnetite. Confocal Raman spectroscopy analyses indicate that the garnet porphyroblasts are of almandine composition. Their chemical structural formulas were determined as Alm0.80-0.88Prp0.07-0.13Grs0.01-0.07Sps0.00-0.05. Garnet-biotite geothermometry calculations suggest that the garnets crystallized under average pressure conditions of ~4.5 kbar at temperatures of 465.4±41.6 °C. Multi-element variation diagrams normalized to the lower and upper continental crust indicate depletion in LIL elements (Sr, K, Rb and Ba), whereas enrichment is observed in HFS elements (Ta, P, Zr, Hf and Y). Chondrite-normalized multi-element diagrams show up to 100-fold enrichment in Rare Earth Elements (REE) (∑REE: 162.1-284.9; (La/Sm)N = 1.65-3.62; (Sm/Yb)N = 0.43-0.67). Enrichment Factor (EF) calculations from chemical analyses highlight the role of Co, Fe, U and Mn elements in color development. These findings are further supported by EPMA data and optical absorption spectroscopy, both of which confirm the predominant presence of Fe+2 ions. Mineralogical, geochemical and gemological investigations indicate that the Ekinözü garnet porphyroblasts formed under greenschist facies metamorphic conditions. Their euhedral crystal morphology, together with their dark red coloration and vitreous luster, suggests that these garnets have potential for use as gemstones in jewelry.

Keywords

• Garnet porphyroblasts
• Raman spectroscopy
• Mineral chemistry
• Gemology
• Gemstone

Granat porfiroblastlarının (Ekinözü-Kahramanmaraş) mineralojik-petrografik özellikleri, metamorfizma koşullarının belirlenmesi ve süs taşı potansiyeli

Öz

Çalışma konusu olan granat porfiroblastları Ekinözü (Kahramanmaraş) bölgesinde farklı mineralojik bileşime sahip şistlerden oluşan metamorfik kayaçlar içerisinde bulunmaktadır. Pentagonal dodekahedron formda kristallenmiş olan granat porfiroblastlarının boyutları 0.5 - 4 cm arasında değişmekte olup koyu kırmızı, kırmızımsı siyah renkte camsı parlaklığa sahiptirler. Mikroskop incelemelerinde oldukça kırıklı-çatlaklı bir yapıda olan granat porfiroblastları kuvars, klorit ve ilmenit-manyetit türü opak mineral kapanımları içermektedir. Konfokal Raman spektroskopisi analizlerine göre granat porfiroblastları almandin bileşimindedirler. Granat porfiroblastlarının kimyasal yapı formülleri Alm0.80-0.88Prp0.07-0.13Grs0.01-0.07Sps0.00-0.05 olarak belirlenmiştir. Granat-biyotit jeotermometre sonuçları, granatların yaklaşık 4.5 kbar basınç ve 465.4±41.6 °C sıcaklık koşullarında kristalleştiklerini göstermektedir. Alt ve üst kıta kabuğu değerlerine göre normalleştirilmiş çoklu element diyagramları, Ekinözü granat porfiroblastlarının LIL elementleri (Sr, K, Rb ve Ba) açısından tüketildiğini, buna karşılık HFS elementleri (Ta, P, Zr, Hf ve Y) yönünden zenginleştiğini ortaya koymaktadır. Çoklu elementlerin kondrite normalize edilerek değerlendirildiği diyagramlarda, granat porfiroblastlarının Nadir Toprak Element bakımından yaklaşık 100 kata ulaşan zenginleşmeler gösterdiği saptanmıştır (∑NTE: 162.1-284.9; ((La/Sm)N=1.65-3.62); ((Sm/Yb)N=0,43-0,67). Kimyasal analizlerden elde edilen Zenginleşme Faktörü hesaplamaları, özellikle Co, Fe, U ve Mn elementlerinin renk oluşum sürecinde etkili olduğunu göstermektedir. EPMA analizleri ile optik absorpsiyon spektroskopisi de bu bulguları destekleyerek Fe+2 iyonunun baskın varlığını ortaya koymaktadır. Mineralojik, jeokimyasal ve gemolojik incelemeler sonucunda Ekinözü granat porfiroblastlarının yeşilşist fasiyesine karşılık gelen metamorfizma şartlarında oluştukları, öz şekilli kristal yapısına sahip olması ve koyu kırmızı renkte camsı parlaklık göstermesi nedeniyle mücevheratta kullanılabileceği değerlendirilmektedir.

Anahtar Kelimeler

• Granat porfiroblastları
• Raman spektroskopisi
• Mineral kimyası
• Gemoloji
• Süs taşı

Kaynakça

1. [1] Stockton CM, Manson DV. “A proposed new classification for gem-quality garnets”. Gems & Gemology, 21(4), 205-218, 1985.
2. [2] Deer WA, Howie RA, Zussman J. An Introduction to the Rock Forming Minerals. 2nd ed. London, England, Longman, 1992.
3. [3] King RJ. “Minerals explained 26: The garnets”. Geology Today, 15(1), 34-37, 1999.
4. [4] Wehlus T, Körner T, Leitenmeier S, Heinrich A, Stritzker B. “Magneto‐optical garnets for integrated optoelectronic devices”. Physica Status Solidi (a), 208(2), 252-263, 2011.
5. [5] Baxter EF, Caddick MJ, Ague JJ. “Garnet: common mineral, uncommonly useful”. Elements, 9(6), 415-419, 2013.
6. [6] Baxter EF, Caddick MJ, Dragovic B. “Garnet: a rock-forming mineral petrochronometer”. Reviews in Mineralogy and Geochemistry, 83, 469-533, 2017.
7. [7] Klein C, Philpotts A. Earth Materials: Introduction to Mineralogy and Petrology. 2nd ed. Cambridge, England, Cambridge University Press, 2017.
8. [8] Koralay T, Ören U. “Determination of spectroscopic features and gemstone potential of garnet crystals from the Çamköy region (Aydın - SW Turkey) using XRPD, XRF, Confocal Raman Spectroscopy, EPMA and gemological test methods”. Periodico di Mineralogia, 89, 105-123, 2020.

9. [9] Yavuz F, Yıldırım DK. “WinGrt, a Windows program for garnet supergroup minerals”. Journal of Geosciences, 65, 71-95, 2020.
10. [10] Liang P, Zhang Y, Xie Y. “Chemical composition and genesis implication of garnet from the Laoshankou Fe-Cu-Au deposit, the northern margin of East Junggar, NW China”. Minerals, 11(3), 334, 2021.
11. [11] International Gem Society. “Garnet Symbolism”. https://www.gemsociety.org/article/garnet-symbolism-legends/(04.05.2022).
12. [12] Ören U, Koralay T. “Evaluation of garnet phenocrysts in volcanic rocks (Görece/İzmir - Western Türkiye) for their usability as a semi-precious gemstone by multi-analytical methods”. Spectroscopy Letters, 57(7), 388-411, 2024.
13. [13] Perinçek D, Kozlu H. “Stratigraphy and structural relation of the units in the Afşin-Elbistan-Doğanşehir region”. International Symposium on the Geology of the Taurus Belt, Ankara, Türkiye, 26-29 September 1983.
14. [14] Bedi Y, Usta D, Özkan MK, Beyazpirinç M, Yıldız H, Yusufoğlu H. “Doğu Toroslar’da (Göksun-Sarız-Elbistan) allokton istiflerin tektono-stratigrafik özellikleri”. 58. Türkiye Jeoloji Kurultayı, Ankara, Türkiye, 11-15 April 2005.
15. [15] Yılmaz Y, Gürpınar O, Kozlu H, Gül MA, Yiğitbaş E, Yıldırım M, Genç ŞC, Keskin M. Türkiye Petrolleri Anonim Ortaklığı. “Maraş kuzeyinin jeolojisi (Andırın-Berit-Engizek-Nurhak-Binboğa Dağları)”. Ankara, Türkiye, 2028, 1987 (unpublished).
16. [16] Önalan M. “Kahramanmaraş Tersiyer kenar havzasının jeolojik evrimi”. Türkiye Jeoloji Kurultayı Bülteni, 31, 1-10, 1988.
17. [17] Genç ŞC, Yiğitbaş E, Yılmaz Y. “Berit metaofiyolitinin jeolojisi”. A. Suat Erk Jeoloji Sempozyumu, Ankara, Türkiye, 2-5 September 1991.
18. [18] Baydar O, Yergök AF. “Güneydoğu Anadolu-Kenar Kıvrım Kuşağı-Amanos Dağları Kuzeyi ve Doğu Torosların jeolojisi”. Jeoloji Etütleri Dairesi, Ankara, 90 p., 1996 (unpublished).
19. [19] Yılmaz Y, Yiğitbaş E, Genç ŞC, Şengör AMC. Geology and Tectonic Evolution of the Pontides. Editor: Robinson AG. Regional and petroleum geology of the Black Sea and surrounding region, 183-226, Oklahoma, USA, AAPG Memoir, 1997.
20. [20] Yümün Z, Kiliç A. “Kamandağı ile Camdere köyü arasının stratigrafisi”. Cumhuriyet Üniversitesi Mühendislik Fakültesi Dergisi Seri A - Yerbilimleri, 19(2), 16-24, 2002.
21. [21] Candan O, Çetinkaplan M, Topuz G, Koralay OE, Oberhänslı R, Yiğitbaş E, Li Q. “Berit yöresindeki (Kahramanmaraş) eklojit-granat piroksenitlere ait ön bulgular”. 65. Türkiye Jeoloji Kurultayı, Ankara, Türkiye, 2-6 Nisan 2012.
22. [22] Yalçın C. Çağlayancerit (Kahramanmaraş) Batısının Tektono-Stratigrafisi ve Yapısal Evrimi. MSc Thesis, Kahramanmaraş Sütçü İmam University, Kahramanmaraş, Türkiye, 2012.
23. [23] Hozatlıoğlu D, Bozkaya Ö, Yalçın H, Yılmaz H. “Göksun, Afşin ve Ekinözü (Kahramanmaraş) bölgesinde yüzeylenen metamorfik masiflerin minerolojik karakteristikleri”. MTA Journal, 162, 105-146, 2020.
24. [24] Stockton CM, Manson DV. “Scanning electron microscopy in gemology”. Gems & Gemology, 17(2), 72-79, 1981.
25. [25] McMillan PF. “Raman spectroscopy in mineralogy and geochemistry”. Annual Review of Earth and Planetary Sciences, 17, 225-283, 1989.
26. [26] Frost R, Kloprogge T, Schmidt J. “Non-destructive identification of minerals by Raman microscopy”. Journal of Internet Vibrational Spectroscopy, 3, 1-13, 1999.
27. [27] Hope GA, Woods R, Munce CG. “Raman microprobe mineral identification”. Minerals Engineering, 14, 1565-1577, 2001.
28. [28] Mayo DW, Miller FA, Hannah RW. Course Notes on the Interpretation of Infrared and Raman Spectra. Hoboken, NJ, USA, John Wiley & Sons, 2004.
29. [29] Fritsch E, Rondeau B, Hainschwang T, Karampelas S. Raman Spectroscopy Applied to Gemmology. Editors: Dubessy J, Caumon M-C, Rull F. Raman Spectroscopy Applied to Earth Sciences and Cultural Heritage, 455-489, Middlesex, United Kingdom, Mineralogical Society of Great Britain & Ireland 2012.
30. [30] Güllü B, Kadıoğlu YK. “Use of tourmaline as a potential petrogenetic indicator in the determination of host magma: CRS, XRD and PED-XRF methods”. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 183, 68-74, 2017.
31. [31] Akçe MA, Kadıoğlu YK. “Raman spektroskopisinin ilkeleri ve mineral tanımlamalarında kullanılması”. Nevşehir Bilim ve Teknoloji Dergisi, 9(2), 99-115, 2020.
32. [32] Koralay T, Ören U. “Determination of spectroscopic features and gemstone potential of garnet crystals from the Çamköy region (Aydın - SW Turkey) using XRPD, XRF, Confocal Raman spectroscopy, EPMA and gemological test methods”. Periodico di Mineralogia, 89, 105-123, 2020.
33. [33] Deniz K. “Mica Types as indication of magma nature, Central Anatolia, Turkey” Acta Geologica Sinica, 96(3), 844-857, 2022.
34. [34] Moore RK, White WB, Long TV. “Vibrational spectra of the common silicates: I. the garnets”. American Mineralogist, 56, 54-71, 1971.
35. [35] Hofmeister AM, Chopelas A. “Vibrational spectroscopy of end-member silicate garnets”. Physics and Chemistry of Minerals, 17, 503-526, 1991.
36. [36] Kolesov BA, Geiger CA. “Raman spectra of silicate garnets”. Physics and Chemistry of Minerals, 25, 142-151, 1998.
37. [37] Bersani D, Lottici P.P. “Applications of Raman Spectroscopy to Gemology”. Analytical and Bioanalytical Chemistry, 397, 2631-2646, 2010.
38. [38] Jenkins A.L., Larsen R.A. “Gemstone Identification Using Raman Spectroscopy”. Spectroscopy, 19(4), 20-25, 2004.
39. [39] RRUFF. “Database of Raman spectroscopy”. http://rruff.info/almandine/R060099 (15.07.2022).
40. [40] RRUFF. “Database of X-ray diffraction”. http://rruff.info/repository/sample_child_record_powder/by_minerals/Almandine__R060099-9__Powder__DIF_File__10051.txt (12.12.2019).
41. [41] RRUFF. “Database of X-ray diffraction”. https://rruff.info/repository/sample_child_record_powder/by_minerals/Andradite__R060326-9__Powder__Xray_Data_XY_Processed__4295.txt (12.12.2019).
42. [42] RRUFF. “Database of X-ray diffraction”. http://rruff.info/repository/sample_child_record_powder/by_minerals/Grossular__R040066-1__Powder__DIF_File__3313.txt (12.12.2019).
43. [43] RRUFF. “Database of X-ray diffraction”. http://rruff.info/repository/sample_child_record_powder/by_minerals/Pyrope__R100153-9__Powder__DIF_File__11226.txt (12.12.2019).
44. [44] RRUFF. “Database of X-ray diffraction”. http://rruff.info/repository/sample_child_record_powder/by_minerals/Spessartine__R060177-1__Powder__DIF_File__6682.txt (12.12.2019).
45. [45] Klimpel F, Bau M, Graupner T. “Potential of garnet sand as an unconventional resource of the critical high‐technology metals scandium and rare earth elements”. Scientific Reports, 11, 5306, 2021.
46. [46] Zirakparvar NA. “Industrial garnet as an unconventional heavy rare earth element resource: Preliminary insights from a literature survey of worldwide garnet trace element concentrations”. Ore Geology Reviews, 148, 2022.
47. [47] Rudnick RL, Gao S. Composition of the Continental Crust. Editor: Rudnick RL. Treatise on Geochemistry, 1-64, Devon, United Kingdom, Elsevier, 2004.
48. [48] McDonough WF, Sun S. “The composition of the Earth”. Chemical Geology, 120, 223-253, 1995.
49. [49] Evensen NM, Hamilton PJ, O’Nions RK. “Rare earth abundances in chondritic meteorites”. Geochimica et Cosmochimica Acta, 42, 1199-1212, 1978.
50. [50] Wright WI. “The composition and occurrence of garnets”. American Mineralogist, 23, 436-449, 1938.
51. [51] Grew ES, Locock AJ, Mills SJ, Galuskina IO, Galuskin EV, Hålenius U. “Nomenclature of the garnet supergroup”. American Mineralogist, 98(4), 785-811, 2013.
52. [52] Thompson AB. “Mineral reactions in pelitic rock. II. Calculation of some P-T-X (Fe-Mg) phase reactions”. American Journal of Science, 276, 425-454, 1976.
53. [53] Holdaway MJ, Lee SM. “Fe-Mg cordierite stability in high-grade pelitic rocks based on experimental, theoretical and natural observations”. Contributions to Mineralogy and Petrology, 63(2), 175-198, 1977.
54. [54] Ferry JM, Spear FS. “Experimental calibration of the partitioning of Fe and Mg between biotite and garnet”. Contributions to Mineralogy and Petrology, 66, 113-117, 1978.
55. [55] Hodges KV, Spear FS. “Geothermometry, geobarometry and the Al2SiO5 triple point at Mt. Moosilauke, New Hampshire”. American Mineralogist, 67, 1118-1134, 1982.
56. [56] Perchuk LL, Lavrenteva IV. Experimental Investigation of Exchange Equilibria in the System Cordierite-Garnet-Biotite. Editor: Saxena SK. Kinetics and Equilibrium in Mineral Reactions. Advances in Physical Geochemistry, 199-239, New York, USA, Springer, 1983.
57. [57] Dasgupta S, Sengupta P, Guha D, Fukuoka M. “A refined garnet-biotite Fe-Mg exchange geothermometer and its application in amphibolites and granulites”. Contributions to Mineralogy and Petrology, 109, 130-137, 1991.
58. [58] Bhattacharya A, Mohanty L, Maji A, Sen SK, Raith M. “Non-ideal mixing in the phlogopite-annite binary: Constraints from experimental data on the Mg-Fe partitioning and a reformulation of the biotite-garnet thermometer”. Contributions to Mineralogy and Petrology, 111, 87-93, 1992.
59. [59] O’Donoghue M. Gems: Their Sources, Descriptions and Identification. Oxford, England, Elsevier, 2006.
60. [60] Rossman GR. “The geochemistry of gems and its relevance to gemology: Different traces, different price”. Elements, 5(3), 159-162, 2009.
61. [61] Galoisy L. “Garnets: From stone to star”. Elements, 9, 453-456, 2013.
62. [62] Barbieri M. “The importance of enrichment factor (EF) and geoaccumulation index (IGEO) to evaluate the soil contamination”. Journal of Geology & Geophysics, 5, 237-240, 2016.
63. [63] Schmetzer K, Hainschwang T, Kiefert L, Bernhardt HJ. “Pink to pinkish orange malaya garnets from Bekily, Madagascar”. Gems & Gemology, 37(4), 296-308, 2001.
64. [64] Ören U. Türkiye’de Seçili Granatların Mineralojik, Petrografik, Spektroskopik, Jeokimyasal ve Gemolojik Özelliklerinin Belirlenmesi. PhD Thesis, Pamukkale University, Denizli, Türkiye, 2023.