J 2021

Magnesio-lucchesiite, CaMg3Al6(Si6O18)(BO3)3(OH)3O, a new species of the tourmaline supergroup

SCRIBNER, Emily D., Jan CEMPÍREK, Lee A. GROAT, R. James EVANS, Cristian BIAGIONI et. al.

Základní údaje

Originální název

Magnesio-lucchesiite, CaMg3Al6(Si6O18)(BO3)3(OH)3O, a new species of the tourmaline supergroup

Autoři

SCRIBNER, Emily D., Jan CEMPÍREK (203 Česká republika, garant, domácí), Lee A. GROAT, R. James EVANS, Cristian BIAGIONI, Ferdinando BOSI, Andrea DINI, Ulf HÅLENIUS, Paolo ORLANDI a Marco PASERO

Vydání

American Mineralogist, Mineralogical Society of America, 2021, 0003-004X

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10504 Mineralogy

Stát vydavatele

Spojené státy

Utajení

není předmětem státního či obchodního tajemství

Odkazy

Impakt faktor

Impact factor: 3.066

Kód RIV

RIV/00216224:14310/21:00119211

Organizační jednotka

Přírodovědecká fakulta

UT WoS

000673958300002

Klíčová slova anglicky

Magnesio-lucchesiite; new mineral species; lamprophyre dike; O'Grady Batholith; San Piero in Campo; Elba Island; Lithium; beryllium and boron: Quintessentially crustal

Štítky

Příznaky

Mezinárodní význam, Recenzováno
Změněno: 17. 9. 2021 15:42, doc. Mgr. Jan Cempírek, Ph.D.

Anotace

V originále

Magnesio-lucchesiite, ideally CaMg3Al6(Si6O18)(BO3)3(OH)3O, is a new mineral species of the tourmaline supergroup. The holotype material was discovered within a lamprophyre dike that cross-cuts tourmaline-rich metapelites within the exocontact of the O’Grady Batholith, Northwest Territories (Canada). Two additional samples were found at San Piero in Campo, Elba Island, Tuscany (Italy) in hydrothermal veins embedded in meta-serpentinites within the contact aureole of the Monte Capanne intrusion. The studied crystals of magnesio-lucchesiite are black in a hand sample with vitreous luster, conchoidal fracture, an estimated hardness of 7–8, and a calculated density of 3.168 (Canada) and 3.175 g/cm3 (Italy). In plane-polarized light, magnesio-lucchesiite is pleochroic (O = dark brown, E = colorless) and uniaxial (–); its refractive index values are nω = 1.668(3) and nε = 1.644(3) (Canada), and nω = 1.665(5) and nε = 1.645(5) (Italy). Magnesio-lucchesiite is trigonal, space group R3m, Z = 3, with a = 15.9910(3) Å, c = 7.2224(2) Å, V = 1599.42(7) Å3 (Canada) and with a = 15.9270(10) Å, c = 7.1270(5) Å, V = 1565.7(2) Å3 (Italy, sample 1). The crystal structure of magnesio-lucchesiite was refined to R1 = 3.06% using 2953 reflections with Fo > 4σ(Fo) (Canadian sample; 1.96% / 1225 for the Italian sample) The Canadian (holotype) sample has the ordered empirical formula X(Ca0.60Na0.39K0.01)Σ1.00Y(Mg2.02Fe2+0.62Fe3+0.09Ti0.25V0.01Cr0.01)Σ3.00Z(Al5.31Fe3+0.69⁠)Σ6.00[T(Si5.98Al0.02)Σ6.00O18](BO3)3V[(OH)2.59O0.41]Σ3.00W(O0.78F0.22)Σ1.00. The Italian (co-type) material shows a wider chemical variability, with two different samples from the same locality having ordered chemical formulas: X(Ca0.88Na0.12)Σ1.00Y(Mg1.45Fe2+0.40Al0.79Fe3+0.36⁠)Σ3.00ZAl6[T(Si5.05Al0.95)Σ6.00O18](BO3)3V[(OH)2.90O0.10]Σ3.00W(O0.98F0.02)Σ1.00 (sample 1) and X(Ca0.71Na0.21☐0.08)Σ1.00Y(Mg2.49Fe2+0.41Ti0.10)Σ3.00Z(Al5.44Fe3+0.46Mg0.09V0.01)Σ6.00[T(Si5.87Al0.13)Σ6.00O18](BO3)3V(OH)3W[O0.61(OH)0.39]Σ1.00 (sample 2). Magnesio-lucchesiite is an oxy-species belonging to the calcic group of the tourmaline supergroup. It is related to lucchesiite by the homovalent substitution YFe ↔ YMg, and to feruvite by the homovalent and heterovalent substitutions YFe ↔ YMg and ZAl3+ + WO2– ↔ ZMg2+ + W(OH)1–. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA 2019-025). Occurrences of magnesio-lucchesiite show that its presence is not restricted to replacement of mafic minerals only; it may also form in metacarbonate rocks by fluctuations of F and Al during crystallization of common uvitic tourmaline. High miscibility with other tourmaline end-members indicates the large petrogenetic potential of magnesio-lucchesiite in Mg, Al-rich calc-silicate rocks, as well as contact-metamorphic and metasomatic rocks.

Návaznosti

GA17-17276S, projekt VaV
Název: Turmalín - indikátor geologických procesů
Investor: Grantová agentura ČR, Turmalín - indikátor geologických procesů