Approaches to the low grade metamorphic history of the karakaya complex by chlorite mineralogy and geochemistry

In this study, chlorite is used to investigate the diagenetic-metamorphic evolution and accurate geological history of the different units belonging to the Karakaya complex, Turkey. Primary and secondary chlorite minerals in the very low-grade metamorphic rocks display interference colors of blue and brown and an appearance of optical isotropy. Chlorites are present in the matrix, pores, and/or rocks units as platy/flaky and partly radial forms. X-ray diffraction (XRD) data indicate that Mg-Fe chlorites with entirely IIb polytype (trioctahedral) exhibit a variety of compositions, such as brunsvigite-diabantite-chamosite. The major element contents and structural formulas of chlorite also suggest these were derived from both felsic and metabasic source rocks. Trace and rare earth element (REE) concentrations of chlorites increase with increasing grade of metamorphism, and these geochemical changes can be related to the tectonic structures, formational mechanics, and environments present during their generation. © 2015 by the authors; licensee MDPI, Basel, Switzerland

Clay mineralogy, chemistry, and diagenesis of late devonian K-bentonite occurrences in northwestern Turkey

Thin beds of tephra (K-bentonites) formed by the diagenesis of volcanic ash are exposed within the limestone-dolomitic limestone successions of the Yilanli formation at Zonguldak and Bartin in northwestern Turkey. They were deposited on the Middle Devonian-Lower Carboniferous shallow carbonate platform of the Zonguldak terrane. In this study, K-bentonite samples collected from Gavurpinari and Yilanli Burnu limestone quarries are investigated in order to reveal their mineralogical and geochemical characteristics and diagenetic evolution. Illite is the major clay mineral in the studied K-bentonites. Additionally, kaolinite and mixed-layer illite-smectite are identified in some samples. The nonclay minerals calcite, dolomite, quartz, gypsum, feldspar, pyrite, and zircon are also found. Crystal-chemical characteristics (Kiibler index, d060 values, and polytypes of illites) from two different sampling locations do not show significant variations. Kiibler index values for the Yilanli Burnu and Gavurpinari sampling locations, 0.47-0.93 (average: 0.71 A°29) and 0.69-0.77 (average: 0.72 A°29), respectively, indicate that illites were affected by high-grade diagenetic conditions. The swelling (or smectite) component (~5%), crystallite size (N = 10-20 nm), and polytype (2M1 > 1Md) data of illites support the same conditions. Illite d060 values of 1.491-1.503 A correspond to a range of octahedral Mg+Fe values of 0.27-0.51 atoms per formula, indicating a composition between end-member muscovite and phengite unit. Trace and rare earth element-based chemical classification of the K-bentonite samples revealed that composition of original volcanic ash is basaltic. Illitization took place by fixation of K from volcanic minerals and ash, and diffusion of elements (Mg+Fe) into and out of the beds during diagenesis. Mineralogical-chemical data point out that these K-bentonites evolved in high-grade diagenetic conditions (approximately 100-150 °C) from the products of volcanic eruptions of disputed sources and distances during the Late Devonian time. © 2015 TÜBİTAK

Diagenetic history of the rock units of bozkir unit controlled by the triassic rifting, Bozkır-Konya

The Bozkir Unit representing the northern edge of the Taurus Belt. It comprises from bottom to top, three distinct structural entities: the Upper Triassic pre-rift (Korualan Group), the Upper Triassic-Upper Cretaceous syn-rift (Huglu Group) and the Jurassic-Cretaceous Boyali Tepe Group as to their structural settings. The Korualan Group is represented by the alternations of carbonate (limestone, dolomitic limestone, dolomite) with radiolarite and chert intercalations and clastic rocks (sandstone, siltstone, mudstone, shale). The Huglu Group is made up of volcanic (basalt, andesite) and pyroclastic (tuffaceous sandstone) rocks including radyolarite, limestone and clastic rock (sandstone, siltstone, shale) intercalations. The Boyali Tepe Group is completely made of carbonate rocks. The carbonate-silisiclastic-volcanogenic rocks of the Bozkir Unit contain carbonate (calcite, dolomite), quartz, feldspar (plagioclase, anortoclase), phyllosilicate (illite, chlorite, mixed-layered illite-chlorite/I-C, chlorite-vermiculite/C-V, chlorite-smectite/C-S, rarely smectite), augite, hematite, analcime and heulandite in order of abundance. On the basis of illite Kübler Index data; Korualan Group and Huglu Group re?ect low grade diagenetic, high grade diagenetic and high grade diagenetic-anchizonal characteristics, respectively. The illite/micas of the pre-rift units and units related to the rifting have muscovitic, and phengitic and seladonitic compositions, respectively. The distributions of chondrite-normalized trace and rare earth element (REE) contents in the illites present similar trends for Korulan ve Huglu groups, but the quantities of these elements slightly increase in the Huglu Group. δ18O-dD isotopic compositions of water forming the illite minerals are different than that of sea water and found to be between Eastern Mediterranean Meteoric Water (EMMW) and magmatic water compositions. It also shows that temperature of the water forming the illite minerals varies from low to high values. The fndings from the rocks of Bozkir Unit suggest that pre-and syn-rift units have different mineralogical-petrographical and geochemical properties. The younger units within the rift due to extension and crustal thinning related to rifting must have exposed in higher diagenetic conditions by more burial and heat with respect to older units at the edges

The pioneer work of Bernard Kübler and Martin Frey in very low-grade metamorphic terranes: paleo-geothermal potential of variation in Kübler-Index/organic matter reflectance correlations. A review

Low-temperature metamorphic petrology occupies the P-T field between sedimentary and metamorphic petrology. Two important pillars of low-temperature metamorphism are coal petrology and clay mineralogy. When low temperature petrology was established bridging a hiatus between the two classical geological disciplines of sedimentary geology and metamorphic petrology, geologists faced a need for the usage of different terminology tenets. Martin Frey and Bernard Kübler were two pioneers in low-grade metamorphic petrology. They focused their research on clarifying the relationships of clay mineralogy and organic petrology to metamorphic pressure (P) and temperature (T) conditions. The ultimate aim of M. Frey and B. Kübler was to establish a correlation between clay indices and organic parameters for different geodynamic setting and therefore for various pressure-temperature (P-T) conditions occurring in low grade metamorphic terranes. For this purpose, a special attention was addressed to the correlation between the Kübler-Index (KI) and vitrinite reflectance (VR). All these efforts are dedicated to estimate the P-T conditions and thus to gain insight into the geodynamic evolution of low-grade metamorphic terranes. B. Kübler and M. Frey honored here concentrated their studies to the Helvetic Central Alps area. The very low-grade Helvetic domain is therefore of basic interest of this paper. Ensuing the extensive compilation of data from the Helvetic domain, a reinterpretation of Kübler and Frey's research is presented in the light of last decade's scientific progress. A comprehensive dataset available enables to discriminate many factors influencing the Kübler-Index and organic-matter reflectance alongside to time, temperature and pressure. The correlation is restricted to the KI and organic matter reflectance (mostly VR) because most of the studies used both methods. Organic matter reflectance (OMR) includes data from vitrinite reflectance and bituminite reflectance measurements. Geodynamics has important control on the KI/VR (OMR) correlation. Tectonic units having a similar geodynamic evolution are featured by the comparable KI/OMR trends, related to the particular paleo-geothermal conditions. Obviously the KI/OMR correlations provide a mean to characterise geothermal gradients and metamorphic very-low-grade pressure-temperature conditions. In terranes where high deformations rates are reported, exceeding the high anchizone conditions, strain promotes the kinetic effects of temperature and pressure on the KI versus OMR rati

Illite occurrences related to volcanic-hosted hydrothermal mineralization in the biga peninsula, NW Turkey: Implications for the age and origin of fluids

A different approach to investigate the origin of fluids, temperature conditions, age of hydrothermal activity of mineralization in the Biga Peninsula, (Koru, Tesbihdere and Kumarlar) employed mineralogical (illite Kübler index, b cell dimension, polytype) and geochemical (major, trace/REE, O-H stable isotope and Rb/Sr dating) methods. The Kübler Index (KI) values of illites indicate different temperature conditions, such as low temperature (high-grade diagenesis) for Koru deposit, and high temperature (anchizone) for the Tesbihdere and Kumarlar deposits. The textural, mineralogical and geochemical data from illites show that these have potential for estimating the age of hydrothermal activity and fluid characteristics. Both mineralogical (high grade diagenetic to anchizonal KI, 1 M polytype, low d060 values) and geochemical (similar major and trace element composition to host-rocks, low octahedral Mg + Fe contents, oxygen and hydrogen isotope composition) data are compatible with commonly known hydrothermal illites. Stable isotope data of illites are well matched to similar data from fluid inclusions, which indicate mainly magmatic fluids. The Rb/Sr age (22.4 ± 2.3 Ma: latest Oligocene and lowest Miocene) of the illites coincides with plutonic intrusions that are the main instigators of hydrothermal activities related to the extensional tectonic regime in the Biga Peninsula. The mineralogical and geochemical data of illites have some important advantages with respect to the use of fluid inclusions in determining δD of hydrothermal fluids thereby leading to better understanding ore-forming hydrothermal condition

Mineral Chemistry of Low-Temperature Phyllosilicates in Early Paleozoic Metaclastic Rocks, Eastern Tauride Belt, Türkiye

The mineral chemistry of illite/mica and chlorites, together with the evaluation of textural data of low-temperature metaclastic rocks, plays an important role in determining their origin and metamorphic grade. This study aimed to investigate the chemical properties of phyllosilicates in early Paleozoic metaclastic rocks in the Eastern Tauride Belt, Türkiye. The textural (electron microscopy) and chemical (mineral chemistry analysis) analyses were performed on the samples representing different grades of metamorphism. The illites/micas and chlorites are observed as detrital (chlorite–mica stacks) and neoformation origin. Trioctahedral chlorites (chamosite) exhibit different chemistry for detrital and neoformed origin as well as the metamorphic grade. Tetrahedral Al and octahedral Fe + Mg increase, whereas octahedral Al decreases together with the increasing grade of metamorphism. The detrital chlorites have higher tetrahedral Al and Fe contents than their neoformed counterparts. Chlorite geothermometry data (detrital: 241–≥350 °C; neoformed: 201–268 °C) are compatible with the texture and illite Kübler index data. Illite/white-mica compositions display muscovite and Na-K mica. Tetrahedral Al and interlayer K + Na contents of illites/micas increase with metamorphic grade. Na-K mica and paragonite are observed as replacement-type developments within the detrital CMS. The obtained data indicate that phyllosilicate chemistry can be used effectively for determining the geological evolution of low-grade metamorphic sequences

Direct observation and measurement of Au and Ag in epithermal mineralizing fluids

Colloidal gold particles have been observed in c. 300 °C low salinity fluids from the Arapucandere intermediate sulphidation epithermal base-metal-Au deposit in NW Turkey. This is the first time colloidal gold has been recorded in an ancient mineralizing fluid. Growth, in veins, of large euhedral quartz crystals, after the deposition of sulphides, occurred in a number of stages from the introduction of fresh pulses of fluid. The quartz overgrowths have a fibrous texture which facilitated trapping of large elongate fluid inclusions between the quartz fibres which grew perpendicular to the crystal faces of the pre-existing quartz. Episodic periods of intense trapping of fluid inclusions occurred throughout the growth of quartz. Trapped within primary fluid inclusions are numerous particles of gold, the largest observed is c. 1 µm but most are smaller. BSE element mapping shows these to contain Au, Ag, Cu ± Hg. LA-ICP-MS profiles of the fluid inclusions confirm Au and Ag is not present in solution, being present as numerous particles. We have quantified the concentration of gold in fluid inclusions which are orders of magnitude greater than has been previously measured or thought likely in crustal fluids. The average Ag concentration is c. 32 ppm and Au is c. 41 ppm but the maximum concentrations of both may reach several 100’s to 1000 ppm. Calcite forms a coating on the inner surface of the inclusions and barite, pyrite, galena, sphalerite and unidentified minerals are also present with the Au-Ag particles. It is clear that the Au-Ag particles could not have precipitated in the fluid inclusions, therefore they must have precipitated elsewhere and been carried with the hydrothermal fluid. The high concentrations and their colloidal nature have implications for the enrichment of gold in mineral deposits. © 2019 Elsevier B.V

The presence of colloidal gold in epithermal mineralizing fluids

C1 [Bozkaya, GUlcan; Bozkaya, Omer] Pamukkale Univ, Dept Geol Engn, Pamukkale, Turkey.Transport of gold and silver as colloidal particles has been observed in c. 300 degrees C low salinity fluids from the Arapucandere intermediate sulphidation epithermal base-metal-Au deposit in NW Turkey. Large euhedral quartz crystals, grew after the deposition of sulfides. Overgrowths have a fibrous texture which grew perpendicular to the existing crystal faces and facilitated trapping of large elongate fluid inclusions between the quartz fibres. Episodic trapping of fluid inclusions occurred throughout the growth of quartz. Trapped within primary fluid inclusions are numerous particles of gold, the largest observed is c. 1 mu m but most are smaller. BSE element mapping show these to contain Au, Ag, Cu + Hg. LA-ICP-MS ablation of fluid inclusions confirms Au and Ag is not present in solution, occurring as numerous particles. The concentration of gold in fluid inclusions is orders of magnitude greater than has been previously measured or thought likely in crustal fluids. The average Ag concentration is c. 32 ppm and Au is c. 41 ppm, but the maximum concentrations may reach several 100's to 1000 ppm. Au-Ag particles could not have precipitated in the fluid inclusions, therefore have precipitated elsewhere and transported by the hydrothermal fluid.[Banks, David A.] Univ Leeds, Sch Earth ; Environm, Leeds, W Yorkshire, England

Gözaydın (Bizmişen, Erzincan) Demir Yatağının Kökeninin Belirlenmesinde Sıvı Kapanım, LA-ICP-MS, Raman Spektrometresi ve İzotop Jeokimyası İncelemeleri

Projede, Gözaydın (Bizmisen, Erzincan) bölgesi demir yatagında cevherlesmeyi olusturan sıvıların sıcaklık, kimyasal bilesim (tuzluluk) ve kökeninin (magmatik su, meteorik su) belirlenmesi amaçlanmıstır. Bu kapsamda, cevher mineralleri ve bunlara eslik eden gang mineralleri üzerinde farklı ve gelismis yöntemler uygulanmıstır. Alterasyon ürünleri optik ve taramalı elektron mikroskop (SEM) ve X-ısınları kırınımı (XRD) yöntemleriyle incelenmistir. Ana cevher minerallerine (hematit, manyetit) eslik eden sülfür minerallerinde (pirit ve kalkopirit) kükürt izotopları jeokimyası (?34S), gang ve alterasyon minerallerinde (kalsit, smektit, kaolinit, I- S) ana, iz ve izotop jeokimyası (?18O, ?D, ?13C, 40Ar/39Ar) ve kalsit, kuvars, barit, epidot ve granat minerallerinde sıvı kapanım çalısmaları ve ayrıca ilk kez LAICP- MS ve Raman spektrometresi yöntemleri uygulanmıstır. Diyoritik bilesimli plütonik kayaçlar kireçtası ve ofiyolitlere sokulum yaparak demir cevherlesmesi (skarn, damar/mercek, ornatma ve plaser tipi), killi alterasyon zonu (arjilik alterasyon) ve plütonik kütle içerisinde skarn minerallerinin (granat, diyopsit, epidot, skapolit, tremolit, klorit) olusumuna neden olmustur. Cevher minerallerini manyetit, hematit ve tali miktarda pirit, kalkopirit, kovellin, kalkosin, götit ve limonit, gang minerallerini ise kalsit, kuvars ve barit olustumaktadır. XRD ve SEM incelemelerine göre; diyorit-kireçtası sınırlarında arjilik alterasyonu isaret eden neoforme smektit (Na- ve Ca-smektit), kaolinit, I-S ve illit, diyoritofiyolit sınırlarında flogopit/vermikülit, serpantin (krizotil), talk ve klorit gelismistir. Kalsit, kuvars, barit, epidot ve granatlarda gerçeklestirilen sıvı kapanım incelemeleri; plütonik sokulumla iliskili gang minerallerinin olusumunun düsük-orta tuzluluga sahip çözeltilerce 200- 300 oC arasında, ikincil kapanımlarla temsil edilen cevher minerallerinin orta-yüksek tuzluluga sahip çözeltilerce 350-400 oC arasında olustugunu göstermistir. Kil minerallerinin ana ve iz element bilesimleri diyorit ve ofiyolit bilesimi arasında, diyoritlere daha yakın olup, duraylı izotop jeokimyası verileri kil minerallerini olusturan suların baslıca magmatik sudan türedigini göstermistir. Kil minerallerinin ?18OV-SMOW ve ?DV-SMOW verileri smektitler için süperjen veya düsük dereceli arjilik zonu (100-200 oC); I-S ve kaolinit için hipojen veya yüksek dereceli arjilik zonu (200 oC) isaret etmektedir. Kalsitlerin ?13CVPDB ve ?18OV-SMOW ile pirit ve kalkopiritlerin ?34SV-CDT verileri magmatik kökeni yansıtmaktadır. Kalsit, kuvars, barit ve epidot minerallerindeki sıvı kapanımların LA-ICP-MS analiz verileri (özellikle genis aralık sunan K/Na degerleri, K/Na - Ba/Na ve Zn/Na - Pb/Na dagılımları) uzun süreli hidrotermal aktiviteyi, K-feldispatların ileri düzeyde bozundugunu (yıkıldıgını), indirgen ve yükseltgen kosulları temsil eden sıvı karısımları isaret etmektedir

Sivas-Divriği Demir Yatağı Kireçtaşı-Ofiyolit-Granitoyid Üçlü Dokanağında Flogopit Oluşumları

Güneş Ofiyoliti'ne ait ultramafik kayaçlarda belirlenen bozuşma mineralleri serpantinleşme-öncesi, -sırası ve -sonrası olmak üzere üç ana gruba ayrılmıştır. Bunlardan serpantinleşme-öncesi minerallerden flogopit; ofiyolitik dizilimin oluşumu ile eşzamanlı mika-peridoditlerin ana bileşenlerinden birisidir. Sonraki bozuşmalardan lisfenitleşme ve pirometasomatizma, flogopitlerin tane boyunun artmasına ve belirli zonlarda birikmesine; yer yer karışık tabakalı flogopit-vermikülit (P-V) ve vermikülit dönüşümlerine neden olmuştur. Serpantinleşme-sırasında gelişen bozuşmalar koyu ve açık renkli minerallerin farklı kil ve/veya fillosilikat minerallerine dönüşümüdür. Serpantinleşme-sonrası bozuşma lisfenitleşme olup; başlıca ofikarbonat (yaygın kalsit ve dolomit; ender siderit ve hidrotalsit), ofioksit-hidroksit (hematit, götit, pirit, markasit, brusit) ve yer yer ofisilikat (kuvars) minerallerinin oluşumunu kapsamaktadır. Pirometasomatik kayaçlarda metasomatizma ürünlerini flogopit, aktinolit, epidot, yohansenit, skapolit, şörl ve Fe-mineralleri (manyetit, hematit, pirit, markasit); kalıntı birincil magmatik fazları ise piroksen ve feldispatlar oluşturmaktadır. Divriği flogopitleri; teorik flogopit-biyotit serisi uç üyelerinin oksit bileşimlerinden kısmen farklılık göstermektedir. Flogopitlerin biyotit bileşeni düşük olup, ortalama birim hücre bileşimine göre; Fe-Al flogopit olarak adlandırılmıştır. Ultramafik-ana kayaçlı P-V'in ana bileşeni Mg olup; kısmen Fe'ce zengin ve Al'ca fakirdir. Tetrahedral ve oktahedral Fe sübstitüsyonlara sahip serpantinler Fe-lizarditi işaret etmektedir. Divriği yöresindeki fillosilikat minerallerinin toplam eser element derişimi serpantin-flogopit-P-V yönünde azalmakta, buna karşın nadir toprak element içerikleri artmaktadır. ?18O ve ?D değerleri (SMOW) flogopitler için ? +10.6-11.8 ve ? -64 - -102, P-V için ? +14.2 ve ? -121, serpantin için ? +14.4 ve ? -129 olarak belirlenmiştir. ?18O ve ?D değerlerine göre; flogopitler hipojen ve süperjen alanda; buna karşın P-V ve serpantin ise kaolinit yüzeysel bozunma çizgisinin altında yer almaktadır. Granitik su minimum izotopik değerine göre flogopit için ~ 130-150 °C ve P-V için ~ 100 °C oluşum sıcaklıkları elde edilmiştir. Ayrıca, duraylı izotop verileri, serpantinleşme, flogopitleşme ve vermikülitleşmenin birbirini izleyen farklı süreçler ile oluştuğuna işaret etmektedir