Characterisation of Tourmalines from Different Environments
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DISSERTATION Characterisation of tourmalines from different environments and correlations between structural and chemical data Verfasser Mag. Bakk. rer. nat. Andreas Ertl angestrebter akademischer Grad Doktor der Naturwissenschaften (Dr. rer. nat.) Wien, am 2. März 2009 Studienkennzahl lt. Studienblatt: A 091 426 Dissertationsgebiet lt. Studienblatt: 426 – Erdwissenschaften Betreuer: O. Prof. Dr. E. Tillmanns 2 Table of contents PART 1…………………………………………………………………………………………………6 1 Introduction…………………………………………………………..………………………….6 1.1 General introduction………………………..…………………………………………………….6 1.2 Previous work on the crystal chemistry of tourmaline………………………….……………..…7 1.3 Aim of the present work………………………………………………………………….………9 2 Tourmaline from the elbaite-schorl series from the Himalaya Mine, Mesa Grande, California, U.S.A.: A detailed investigation……………………………………………….….11 2.1 Abstract……………………………………………………………………………………….…11 2.2 Introduction………………………………………………………………………………….….12 2.3 Experimental details…………………………………………………………………………….13 2.3.1 Sample selection………………………………………………………………………..13 2.3.2 Crystal-structure refinement……………………………………………………………14 2.3.3 Chemical analysis………………………………………………………………………15 2.3.4 Spectroscopic investigations…………………………………………………………...17 2.3.5 OH determinations……………………………………………………………………..18 2.3.6 Li NMR spectroscopy………………………………………………………………….18 2.4 Results and discussion……………………………………………………………………...…..19 2.5 Conditions of formation for tourmaline-bearing cavities in the Himalaya dike………………..23 2.6 Acknowledgements……………………………………………………………………………..27 2.7 References……………………………………………………………………………………....28 3 Substitution mechanism in tourmalines of the “fluor-elbaite”-rossmanite series from Wolkenburg, Saxony, Germany………………………………………………………..61 3.1 Abstract…………………………………………………………………………………………61 3.2 Introduction……………………………………………………………………………….…….61 3.3 Methods…………………………………………………………………………………….…...63 3 3.3.1 Sample selection……………………………………………………………………………….63 3.3.2 Crystal structures………………………………………………………………………………63 3.3.3 Chemical analysis……………………………………………………………………………...64 3.4 Results and discussion…………………………………………………………………………66 3.5 Acknowledgements……………………………………………………………………………69 3.6 References……………………………………………………………………………………..69 4 Investigations on Fe2+- and Mn2+-rich tourmaline…………………………………………85 4.1 Abstract………………………………………………………………………………………..85 4.2 Introduction and previous work……………………………………………………………….86 4.3 Experimental details…………………………………………………………………………...87 4.3.1 Crystal-structure refinement…………………………………………………………..87 4.3.2 Chemical analyses…………………………………………………………………….87 4.3.3 Mössbauer analysis……………………………………………………….………......89 4.3.4 Optical sprectra………………………………………………………………….….....89 4.4 Results and discussion…………………………………………………………….…………...89 4.4.1 Mössbauer Results……………………………………………………………….……89 4.4.2 Optical spectra………………………………………………………………………...91 4.4.3 Crystal chemistry and structural analysis……………………………………………..92 4.4.3.1 Fe-rich tourmaline…………………………………………………………....92 4.4.3.2 Mn-rich tourmaline…………………………………………………………..93 4.4.3.3 Oxidation experiments……………………………………………………….97 4.5 Acknowledgements…………………………………………………………………...……….98 4.6 References…………………………………………………………………………...………...98 5 Li-bearing, disordered Mg-rich tourmalines from the pegmatite-marble contact from the Austroalpine basement units (Styria, Austria)……………………………………….120 5.1 Summary……………………………………………………………………………………..120 4 5.2 Introduction………………………………………………………………………………….120 5.3 Geology……………………………………………………………………………………...121 5.4 Experimental………………………………………………………………………………...123 5.4.1 Sample selection…………………………………………………………………….123 5.4.2 Chemical composition………………………………………………………………123 5.4.3 Crystal Structure…………………………………………………………………….123 5.5 Results……………………………………………………………………………………….124 5.5.1 Discussion of the tourmaline structure……………………………………………...124 5.5.2 REEs and trace elements in the tourmalines……………………………………......126 5.5.3 Discussion of the Eu and Yb anomaly in the tourmalines………………………….126 5.5.4 Discussion of the origin of the tourmalines and their pegmatitic host rocks……….126 5.5.5 Discussion of formation temperatures……………………………………………...128 5.5.6 Geochemistry of the micaschists…………………………………………………....128 5.6 Acknowledgements……………………………………………………………………….…129 5.7 References…………………………………………………………………………………...130 6 Metamorphic ultra-high-pressure tourmalines: Structure, chemistry, and correlations to PT conditions………………….…………………………………………..150 6.1 Abstract……………………………………………………………………………………..150 6.2 Introduction and previous work…………………………………………………………….150 6.3 Tourmaline stability and regional geology of the ultra-high-pressure massifs…………......151 6.4 Experimental details………………………………………………………………………...153 6.4.1 Sample selection…………………………………………………………………………….153 6.4.2 Crystal structure refinements………………………………………………………………..153 6.4.3 Chemical analysis…………………………………………………………………………...154 6.5 Results……………………………………………………………………………………....154 6.6 Discussion…………………………………………………………………………………..156 5 6.7 Acknowledgements………………………………………………………………………..157 6.8 References…………………………………………………………………………………158 7 Summary………………………………………………………………………………….177 Zusammenfassung………………………………………………………………………..180 References…………………………………………………………………………………………184 Acknowledgements………………………………………………………………………….........189 Curriculum Vitae……………………………………………………………………………........190 PART 2 – Publications…………………………………………………………………….202 6 PART 1 1 Introduction 1.1 General introduction Tourmaline is an extremely important mineral because of its relevance in the geosciences, for its technical applications and its use as gemstone. The tourmaline group consists of more than a dozen end members, which occur in many different geological environments (e.g., Hawthorne and Henry, 1999). Tourmaline composition gives information on the thermal and fluid history of rocks in which it develops, is intimately associated with some of the world's premier metallic ore deposits, retains chemical signatures of the sources of tourmaline detritus in clastic rocks, yields isotopic evidence for the environmental sources of the boron that makes up tourmaline, is an extremely critical link in the boron cycle on the Earth and has many other useful petrogenetic features (e.g., Dutrow and Henry, 2000; Gaweda et al., 2002; Goerne, 1998; Henry, 2003). Varying chemical compositions of tourmaline reflect the chemical conditions of rocks where tourmaline forms and have been used as an important petrologic indicator of different geologic environments in previous investigations (e.g., Henry and Guidotti, 1985; Jolliff et al., 1986; Dyar et al., 1999; Novák et al., 1999; Selway, 1999; Roda-Robles et al., 2004). Tourmaline belongs to the most common piezo- and pyroelectric materials that are technically used (e.g., Prasad et al., 2005). Natural tourmaline is used for piezoelectric pressure transducers for dynamic pressure measurements (e.g., Wilson, 2003). Tourmaline has a high mechanical stability and is resistant to many acids and alkaline solutions. Tourmalines can be used up to 900 °C, the actual technical limit is 750-780 °C. Additionally, tourmaline displays significant pyroelectricity (e.g., Hawkins et al., 1995; Lally and Cummiskey, 2003). Tourmaline is also used as electronic components, e.g., as transducers, mainly because of the anisotropy of its properties (Adeoye and Adewoye, 2004). More recent applications of tourmaline are in functional fibers (Zhenggang et al., 2005). Tourmaline is also very well known as gemstone which occurs in more colors and combinations of colors than any other gemstone variety; it also shows a remarkable dichroism (e.g., Dietrich, 1985; Dirlam et al., 2002). Tourmaline compositions can also be used as indicator of emerald mineralization (Galbraith, 2007). Tourmalines are complex aluminium-borosilicates with strongly varying compositions because of isomorphous replacements (solid solutions). The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals, with the general formula X Y3 Z6 [T6O18] (BO3)3 V3 W. The structure of tourmaline is characterized by six-membered tetrahedral rings (T sites), whose apical oxygens point toward the (-) c-pole, producing the acentric nature of the structure. 7 In this section the possible occupants of the different sites in the tourmaline structure and the relation between these sites will be discussed. The tetrahedral sites in tourmaline are primarily occupied by Si, and sometimes also (usually) by small amounts of Al and B (e.g., Hawthorne et al., 1993; Ertl et al., 1997, 2003b, 2005, 2006a, 2006c; Hughes et al., 2000, 2004). Above the tetrahedra are triangular BO3 groups that lie parallel to the (0001) plane. Planar rings of tetrahedra are linked by two types of octahedra, Z and Y, which share edges to form brucite-like fragments. The Z octahedron is relatively small, somewhat distorted, and occupied predominantly by trivalent cations such as Al3+, Fe3+, Cr3+ and V3+, but can contain significant amounts of the divalent cations Mg2+ (e.g., Ertl et al., 2002, 2003a). Z-site cations serve as linkages among structural fragments along a three-fold screw axis. The Y site is a relatively regular octahedron occupied by a wide array of multivalent cations, most commonly Li1+, Mg2+, Fe2+, Mn2+, Cu2+, Al3+, Cr3+, V3+, Fe3+, Mn3+ and Ti4+. Most structural refinements indicate that there is minor Y-site vacancy (e.g., Hawthorne et al., 1993; Taylor et al., 1995; Ertl et al., 1997, 2006a). When Fe2+ occurs at the Y site, Mg could not occupy both neighbouring Z sites (Bloodaxe