Fuat Yavuz

Petrology and geochemistry of calc-alkaline volcanic and subvolcanic rocks, Dalli porphyry copper–gold deposit, Markazi Province, Iran

Early Miocene igneous rocks associated with the Dalli porphyry ore body are exposed within the Urumieh-Dokhtar Magmatic Arc (UDMA). The Dalli porphyry Cu–Au deposit is hosted by subduction-related subvolcanic plutons with chemical composition from diorite to granodiorite, which intruded andesitic and dacitic volcanic rocks and a variety of sedimentary sequences. 40Ar/39Ar age data indicate a minimum emplacement age of ∼21 million years for a potasically altered porphyritic diorite that hosts the porphyry system. The deposit has a proven reserve of 8 million tonnes of rock containing 0.75 g/t Au and 0.5% Cu. Chondrite-normalized rare earth element (REE) patterns for the subvolcanic rocks are characterized by light REE enrichments [(La/Sm) n  = 2.57–6.40] and flat to gently upward-sloping profiles from middle to heavy REEs [(Dy/Yb) n  = 0.99–2.78; (Gd/Yb) n  = 1.37–3.54], with no significant Eu anomalies. These characteristics are generated by the fractionation of amphibole and the suppression of plagioclase crystallization from hydrous calc-alkaline magmas. In normalized multi-element diagrams, all analysed rocks are characterized by enrichments in large ion lithophile elements and depletions in high field strength elements, and display typical features of subduction-related calc-alkaline magmas. We used igneous mineral compositions to constrain the conditions of crystallization and emplacement. Biotite compositions plot above the nickel–nickel oxide (NNO) buffer and close to oxygen fugacity values defined by the hematite–magnetite (HM) buffer, indicating oxidizing conditions during crystallization. Assuming a minimum crystallization temperature of 775°C, the oxygen (fO2) and water (fH2O) fugacities are estimated to be 10−10.3 bars (∼ΔNNO+4) and ≤748 bars, respectively, during the crystallization of biotite phenocrysts. The temperature and pressure conditions, estimated from temperature–corrected Al-in-hornblende barometry and amphibole-plagioclase thermometry, suggest that the hornblende phenocrysts in Dalli rocks crystallized at around 780 ± 20°C and 3.8 ± 0.4 kbar. An alternative method using the calcic amphibole thermobarometer indicates that the Dalli magmas were, on average, characterized by an H2O content of 4.3 wt.%, a relatively high oxygen fugacity of 10−11.0 bars (ΔNNO+1.3), and a hornblende phenocryst crystallization temperature of 880 ± 68°C and pressure of 2.6 ± 1.7 kbar.

WinAmphcal: A Windows program for the IMA-04 amphibole classification

A Microsoft© Visual Basic (6.0) program, called WinAmphcal, has been developed to calculate structural formulae of both wet-chemical and microprobe-derived amphibole analyses. On the basis of the standard International Mineralogical Association (IMA-04) classification procedure, WinAmphcal classifies amphibole analyses into five groups and then determines a specific amphibole name with prefixes and modifiers. This software is developed to predict cation site allocations at the different structural positions as well as to estimate stoichiometric Fe3+ and H2O contents from microprobe analyses. If Fe2O3 content is unknown, the program calculates ferric iron content on the basis of the minimum Fe3+ (15eNK) and maximum (13eCNK) criteria considering the site assignments and stoichiometric constraints. Other user-defined calculation and normalization factors can also be carried out by current software for the process of amphibole chemical analyses. Using the charge-balance method, WinAmphcal permits the user to determine the Mn2+ and Mn3+ states from Mn3+-rich microprobe-derived sodic amphiboles. WinAmphcal stores all the calculated results in an Excel file. Hence output of the program can also be displayed and processed by any other software for general data manipulation and graphing purposes.

A revised program for microprobe-derived amphibole analyses using the IMA rules

Abstract A Microsoft QUICKBASIC program with the code name NEWAMPHCAL has been written to calculate the structural formulae of amphibole analyses taken from electron-microprobe, and to determine the classification parameters with the prefixes and modifiers according to the procedures proposed by the International Mineralogical Association (IMA) 1997 amphibole nomenclature scheme. The program, which came up with four Al-in hornblende geobarometers, is applicable to plutonic and its associated volcanic rocks including amphibole–biotite–quartz–plagioclase–ortochlase–sphene–FeTi oxides. An amphibole–plagioclase geothermometer for particular calcic amphiboles also is incorporated into the program structure. NEWAMPHCAL has been tested for determination and classification of numerous amphibole analyses compiled from literature. Depending on the evaluations of selected amphibole analyses by using NEWAMPHCAL program, it was determined that approximately 15% amphibole names were changed compared to the author’s IMA 1978 findings. The most important variation in amphibole names has been observed in the calcic amphibole group. This program permits the user data entry, their storage, and calculation and plotting of microprobe amphibole analyses. NEWAMPHCAL plots the calculated chemical parameters on one ternary and seventeen different binary diagrams for amphibole classification. This software, with well-designed screen forms, stores all the calculated results in comma delimited ASCII file format and thus permits the user to process the program outputs for further spreadsheet applications. A menu-driven and easy to use program runs on IBM-compatible microcomputers under DOS and Windows systems with the minimum hardware requirements. The compiled form of NEWAMPHCAL takes approximately 398 kilobytes together with the test data.

Evaluating micas in petrologic and metallogenic aspect: I-definitions and structure of the computer program MICA

Micas are significant ferromagnesian minerals in felsic to mafic igneous, metamorphic, and hydrothermal rocks. Because of their considerable potential to reveal the physicochemical conditions of magmas in terms of petrologic and metallogenic aspects, mica chemistry is used extensively in the earth sciences. For example, the composition of phlogopite and biotite can be used to evaluate the intensive thermodynamic parameters of temperature (T, °C), oxygen fugacity (fO2), and water fugacity (fH2O) of magmatic rocks. The halogen contents of micas permit the estimation of the fluorine and chlorine fugacities that may be used in understanding the metal transportation and deposition processes in hydrothermal ore deposits. The Mica+ computer program has been written to edit and store electron-microprobe or wet-chemical mica analyses. This software calculates structural formulae and shares out the calculated anions into the I, M, T, and A sites. Mica+ classifies micas in terms of composition and octahedral site-occupancy. It also calculates the intensive parameters such as fO2, T, and fH2O from the composition of biotite in equilibrium with K-feldspar and magnetite. Using the calculated F–OH and Cl–OH exchange systematics and various log ratios (fH2O/fHF, fH2O/fHCl, fHCl/fHF, XCl/XOH, XF/XOH, XF/XCl) of mica analyses. Mica+ gives valuable determinations about the characteristics of hydrothermal fluids associated with alteration and mineralization processes. The program output is generally in the form of screen outputs. However, by using the “Grf” files that come up with this program they can be visualized under the Grapher software both as binary and ternary diagrams. Mica analyses subjected to the Mica+ program were calculated on the basis of 22+z positive charges taking into account the procedure by the Commission on New Mineral Names Mica Subcommittee of 1998.

CLASTOUR: a computer program for classification of the minerals of the tourmaline group

Tourmaline is the most important borosilicate mineral and a dominant carrier of boron, occurring in different geologic environments. Recently, many investigators have focused on the enhanced understanding of crystal chemistry of this complex mineral group. CLASTOUR is a program package for IBM-compatible personal computers that can be used for classification of the tourmaline group. The program classifies most of the currently valid tourmaline end-members together with other hypothetical end-members. Because it is difficult to establish OH- and O2- contents at the V- and W-sites without carrying out bond valance sum (BVS) calculations, CLASTOUR gives alternative names for some tourmalines including dominant O2- anion at their V- and W-sites. The program is developed to edit, to store and to calculate the tourmaline analyses obtained both from electron-microprobe and wet-chemical studies. It is designed to calculate entered tourmaline analyses into cation and molecular percentages, to share cation site-allocations at the different structural positions and to give mole percent of the end-members of alkali-, calcic-, and X-site vacant-group tourmalines. Thus, CLASTOUR makes it possible to plot various types of binary and ternary diagrams under the Grapher software. This program is a user-friendly software with pull-down menus, base-function keys, help menus, extensive error codes and mouse options. The compiled program together with the test data files and graphic files is approximately 1160 kB.

BIOTERM—a program for evaluating and plotting microprobe analyses of biotite from barren and mineralized magmatic suites

Abstract BIOTERM is a DOS-environment software package designed for calculating and interpreting microprobe analyses of biotite from mineralized and barren magmatic rocks. The program permits the user to enter and store data, recalculate chemical analyses, produce a wide variety of binary and ternary compositional plots, determine intensive parameters such as temperature of crystallization, pressure of solidification, and oxygen fugacity where biotite coexists with K-feldspar and magnetite, and estimate the temperature of hydrothermal alteration in porphyry copper mineralization systems. The program is written in QUICKBASIC and runs on PC-compatible computers with a minimum of hardware requirements and a VGA graphics card. The compiled form of BIOTERM takes up approximately 635 kilobytes.

TOURMAL: software package for tourmaline, tourmaline-rich rocks and related ore deposits

Abstract TOURMAL is a user-friendly software package developed for editing, storing, calculating and plotting microprobe tourmaline analyses from different geologic environments such as granites and their related aplites and pegmatites, metasomatic and vein type ore deposits, stratabound base metal deposits, gold deposits, and sedimentary and metamorphic rocks. Calculated results, saved in comma delimited ASCII file format, permit the user to search for other applications related to tourmaline compositions. The program prepares 28 binary and seven ternary diagrams. It is written in Quickbasic for IBM PC and compatibles, and runs under DOS and Windows operating systems with a VGA graphic card. This program permits the user to convert standard binary graphs and ternary diagrams into PCX file format for high quality printouts.

Evaluating micas in petrologic and metallogenic aspect: Part II-Applications using the computer program Mica+

Abstract The significance of micas for metallogenic and petrologic studies results from their widespread occurrence in magmatic, metamorphic, and hydrothermal ore-related rocks. For example, the mineral chemistry of biotites, and especially their halogen content, may provide an important guide in understanding the composition and circulation of fluids during or later emplacement of magmatic rocks and associated with hydrothermal mineralization. The Mica + program has been developed to evaluate mica composition both from magmatic rocks and associated with porphyry copper and Mo–Au–Sn–W–Be systems. The validity of the Mica + program has been tested for variety mica data sets selected from literature. The concept of computer program can be grouped into three major topics, respectively: (i) mica classification and discrimination; (ii); estimation of intensive parameters; and (iii) halogen contents as an indication of hydrothermal ore deposits. Halogen systematics and intensive thermodynamic parameters (i.e., T , f O 2 , f H 2 O) of micas both from porphyry Cu–Au–Mo mineralization system and magmatic rocks were estimated using the Mica + program. Program output was compared with the original published results. Evaluation suggests that the Mica + can be used efficiently in studying the mica composition in respect to petrologic and metallogenic aspects.

WinPyrox: A Windows program for pyroxene calculation classification and thermobarometry

Abstract A Microsoft Visual Basic program, called WinPyrox, has been developed to calculate structural formulas of both wet-chemical and microprobe-derived pyroxene analyses. Based on the standard International Mineralogical Association (IMA-88) nomenclature scheme, WinPyrox primarily calculates and classifies pyroxene groups and then determines a specific pyroxene name with its possible modifiers. It is developed to predict cation site-allocations at the different structural positions, including T, M1, and M2 sites, as well as to estimate end-members, molar fractions, end-member activities, components and activities, and single-clinopyroxene and two-pyroxene thermobarometers. The program allows the user to edit and load Microsoft Excel files to calculate electron-microprobe pyroxene analyses for different ferric iron estimation methods and normalization schemes. This software generates and stores all the calculated results in the output of a Microsoft Excel file, which can be displayed and processed by any other software for verification, general data manipulation, and graphing purposes. The compiled program code is distributed as a self-extracting setup file, including a help file, test data files, and related graphic files, which are designed to produce a high-quality printout from the Golden Software’s Grapher software. The self-extracting setup file, which is approximately 12 Mb, may be downloaded from http://code.google.com/p/winpyrox/ or can be obtained from author on request

Trace-element, rare-earth element and boron isotopic compositions of tourmaline from a vein-type Pb–Zn–Cu ± U deposit, NE Turkey

This paper reports trace-element, rare-earth element (REE) and boron isotopic compositions of tourmaline in the Asarcık granitoid and quartz veins at Şebinkarahisar. Abundant tourmaline occurs in the vein-type Pb–Zn–Cu ± U deposit, within the northeastern Pontide Metallogenic Belt, both within the Late Cretaceous Asarcık granitoid and in associated quartz–tourmaline veins. Tourmaline in the granitoid forms as rosettes up to 1.5 cm in diameter, whereas in quartz–tourmaline veins a few centimetres to a few metres wide, it occurs as black needles and masses that cut the pluton. We present a systematic geochemical study of these tourmalines – all of the schorl-dravite series. Tourmalines from the quartz veins contain high concentrations of ore metals such as Ag, Bi and Zn and have higher Sr, Cr and Sn contents than tourmalines in the Asarcık granitoid. Tourmalines from intensively altered parts of the pluton are characterized by higher concentrations of trace elements such as Ba, Rb, V, Sc, Th and Zr compared with occurrences in the quartz veins and in the fresh and less-altered granitoid. Chondrite-normalized patterns of REEs in tourmalines from the Asarcık granitoid are generally similar to those of tourmalines in the quartz veins. All vein tourmalines, however, are characterized by heavy REE enrichments, in sharp contrast to those in the granitoid. Boron isotopic compositions of tourmalines range from − 14.0 to − 2.2‰ and fall within the δ11B range of this mineral in granite-related settings. Tourmaline rosettes from the Asarcık granitoid show relatively lighter δ11B values ( − 14.0 to − 12.2‰) in comparison with those in the quartz veins ( − 10.4 to − 2.2‰).