Publication detail

The highly siderophile elements and Re-Os isotope geochemistry of Variscan lamproites from the Bohemian Massif: implications for regionally dependent metasomatism of orogenic mantle

KRMÍČEK, L. ACKERMAN, L. HRUBÝ, J. KYNICKÝ, J.

Original Title

The highly siderophile elements and Re-Os isotope geochemistry of Variscan lamproites from the Bohemian Massif: implications for regionally dependent metasomatism of orogenic mantle

Type

journal article in Web of Science

Language

English

Original Abstract

Orogenic lamproites represent a group of peralkaline, ultrapotassic and perpotassic mantle-derived igneous rocks that hold the potential to sample components with extreme compositions from highly heterogeneous orogenic mantle. In our pilot study, we present highly siderophile element (HSE) and Re-Os isotope systematics of Variscan orogenic lamproites sampled in the territories of the Czech Republic, Austria and Poland, i.e., from the termination of the Moldanubian and Saxo-Thuringian zones of the Bohemian Massif. Orogenic lamproites of the Bohemian Massif are distinguished by variably high contents of SiO2 , high Mg# and predominant mineral associations of K-rich amphibole and Fe-rich microcline. The HSE show (i) consistently very low contents in all investigated orogenic lamproites compared to the estimated concentrations in majority of mid-ocean ridge basalts, hotspot-related volcanic rocks (e.g., ocean island basalts, continental flood basalts, komatiites, some intraplate alkaline volcanic rocks such as kimberlites and anorogenic lamproites) and arc lavas, and (ii) marked differences in relative and absolute HSE abundances between the samples from the Moldanubian and Saxo-Thuringian Zone. Such a regional dependence in HSE from mantle-derived melts is exceptional. Orogenic lamproites have highly variable and high initial suprachondritic Os-187/Os-188 values (up to 0.631) compared with rather chondritic to subchondritic Os isotope values of the young lithospheric mantle below the Bohemian Massif. The highly radiogenic Os isotope component in orogenic lamproites may be derived from preferential melting of metasomatised vein assemblages sitting in depleted peridotite mantle. This process appears to be valid generally in the petrogenesis of orogenic lamproites both from the Bohemian Massif and from the Mediterranean area. As a specific feature of the orogenic lamproites from the Bohemian Massif, originally ultra-depleted mantle component correlative with remnants of the Rheic Ocean lithosphere in the Moldanubian Zone was metasomatised by a mixture of evolved and juvenile material, whereas the lithospheric mantle in the Saxo-Thuringian Zone was enriched through the subduction of evolved crustal material with highly radiogenic Sr isotope signature. As a result, this led to observed unique regionally dependent coupled HSE, Rb-Sr and Re-Os isotope systematics.

Keywords

Orogenic mantle; HSE; Re-Os; Lamproites; Saxo-Thuringian Zone; Moldanubian Zone

Authors

KRMÍČEK, L.; ACKERMAN, L.; HRUBÝ, J.; KYNICKÝ, J.

Released

20. 1. 2020

Publisher

ELSEVIER

Location

AMSTERDAM

ISBN

0009-2541

Periodical

CHEMICAL GEOLOGY

Year of study

532

Number

1

State

Kingdom of the Netherlands

Pages from

1

Pages to

11

Pages count

11

URL

http://sciencedirect.com/science/article/abs/pii/S0009254119303973

BibTex

@article{BUT164480,
  author="Lukáš {Krmíček} and Lukáš {Ackerman} and Jakub {Hrubý} and Jindřich {Kynický}",
  title="The highly siderophile elements and Re-Os isotope geochemistry of Variscan lamproites from the Bohemian Massif: implications for regionally dependent metasomatism of orogenic mantle",
  journal="CHEMICAL GEOLOGY",
  year="2020",
  volume="532",
  number="1",
  pages="1--11",
  doi="10.1016/j.chemgeo.2019.119290",
  issn="0009-2541",
  url="http://sciencedirect.com/science/article/abs/pii/S0009254119303973"
}