Hydrothermal alteration of tourmaline from pegmatitic rocks enclosed in serpentinites: Multistage processes with distinct fluid sources

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F21%3A00118781" target="_blank" >RIV/00216224:14310/21:00118781 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1016/j.lithos.2020.105823" target="_blank" >https://doi.org/10.1016/j.lithos.2020.105823</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.lithos.2020.105823" target="_blank" >10.1016/j.lithos.2020.105823</a>

Result language

angličtina

Original language name

Hydrothermal alteration of tourmaline from pegmatitic rocks enclosed in serpentinites: Multistage processes with distinct fluid sources

Original language description

Hydrothermal alteration of primary tourmaline (dravite, oxy-dravite, fluor-dravite,” uvite“, schorl, oxy-schorl, fluor-schorl) and associated plagioclase and quartz is examined in coarse-grained pegmatitic plagioclase-tourmaline rocks, simple granitic pegmatites and zoned beryl-columbite pegmatites, all cutting serpentinite from the Moldanubian Zone, Czech Republic. Tourmaline is replaced by a wide spectrum of minerals—prehnite, pumpellyite-(Al), K-feldspar, chlorite, muscovite, natrolite, arfvedsonite, titanite, epididymite, and hydrous Mg-silicates—and idealized replacement reactions of tourmaline are presented. Secondary mineral assemblages replacing tourmaline and chlorite geothermometry suggest evolution of the PT conditions of tourmaline alteration from T ~ 400–350 °C to 200–100 °C and P &lt; ~1–2 kbar. The replacement processes of tourmaline proceed from the early to late subsolidus stages, and the intensity of tourmaline replacement decreases with decreasing temperature. Alteration typically occurs in small bodies of primitive plagioclase-tourmaline rocks, whereas large, more evolved and locally Li-bearing crosscutting pegmatites exhibit less pronounced tourmaline alteration. Based on the secondary mineral assemblages and types of fluids, four distinct compositional/paragenetic types are defined: Ca,Mg-, Na,K,Mg-, K,Mg- and K,Na-dominant. Sources of fluids include (i) fluids exsolved from pegmatite melt (Na, K, Ca, ± Li), particularly in the more evolved pegmatites, and (ii) fluids infiltrated/diffused from host rocks (Mg, Ca, ± Ni, Cr) at all localities; however, mixing of the fluids is obvious. Boron released from the altered tourmalines into fluids escaped from the system, and the behavior of B in aqueous fluids from granitic pegmatites is discussed. The instability of quartz and tourmaline as well as common late K-feldspar, zeolites, arfvedsonite, and minor smectite suggests alkaline conditions. The alkaline character of fluids promoted by host serpentinite was very likely the main factor affecting tourmaline replacement and the instability of plagioclase, quartz, and other minerals.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

<a href="/en/project/GA17-17276S" target="_blank" >GA17-17276S: Tourmaline – an indicator of geological processes</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2021

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Lithos

ISSN

0024-4937

e-ISSN

1872-6143

Volume of the periodical

380-381

Issue of the periodical within the volume

January

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

19

Pages from-to

„105823“

UT code for WoS article

000612259900003

EID of the result in the Scopus database

2-s2.0-85093648431