Geochemical data for the felsic NGB rocks suggest formation by partial melting or crystal fractionation of a mafic source that was contaminated by older crust, possibly in a back-arc environment.
Initial ε values for NGB rocks range from − 1.2 to 0.3 and suggest involvement of pre-greenstone continental crust that was possibly extensive in the southeastern part of the Kaapvaal Craton during Palaeoarchaean times.► SHRIMP zircon ages confirm that the Nondweni Greenstone belt (NGB) of South Africa, is Palaeoarchaean in age.
WE SPECIALISE IN PRECISE, ACCURATE, HIGH SPATIAL RESOLUTION, URANIUM-THORIUM-LEAD GEOCHRONOLOGY OF ZIRCON, MONAZITE, XENOTIME, TITANITE, ALLANITE, COLUMBITE-TANTALITE, BADDELEYITE, RUTILE, CASSITERITE, OPAL, APATITE, PEROVSKITE, GADOLINITE, CHEVKINITE, ILMENORUTILE, URANINITE AND ZIRCONOLITE.
This work is licensed under the Creative Commons Attribution International License (CC BY). Received 24 August 2014; revised 20 September 2014; accepted 15 October 2014ABSTRACTU/Pb-SHRIMP dating and Pb stepwise leaching (Pb SL) experiments on zircons and garnets, respectively have confirmed the lack of Precambrian outcrops within the crystalline basement of Thailand.
The obtained data for the high grade metamorphism show Indosinian ages ranging from 225 - 200 Ma as previously suggested for the vast majority of outcrops in NW-Thailand ( and references therein), as well as a small group of ages in the range of 445 Ma in the Lampang Province.
The latter date now constrains the age of stromatolite-like structures in cherts associated with the felsic rocks, which probably represent some of the oldest preserved evidence of life on Earth.
The zircon ages also indicate that the NGB correlates well chronologically with the BGB and is one of the oldest volcano-sedimentary successions in the southeastern Kaapvaal Craton.