The genesis of Archean supracrustal rocks in the western Shandong Province of North China Craton: Constraints on regional crustal evolution

Abstract

Archean greenstone belts are supracrustal sequences, the lower part of which is usually composed of voluminous ultramafic-mafic volcanics. Intermediate and acid volcanic rocks increase in abundance towards the upper domains. Greenstone belts constitute ~30% of the total volume of Archean cratons, and preserve significant information on the surface environment and magmatism in the early earth, which are useful in unraveling the nature of crustal formation and evolution. The western Shandong Province (WSP) is located at the eastern part of the North China Craton (NCC), where greenstone sequences formed at ~2.7 and ~2.5 Ga were well preserved. The early Neoarchean supracrustal rocks include komatiite-basalt sequence, some meta-sediments of the lower part of the Taishan Group and the Mengjiatun Formation. The volcanism had been correlated to mantle plume, which resulted in vertical crustal accretion. The late Neoarchean supracrustal rocks were composed of metamorphosed felsic volcano-sedimentary sequences and BIFs of the upper part of the Taishan Group and the Jining Group. The geochemical features of the meta-volcanics show calc-alkaline affinities, similar to modern arc-related magmatism, suggesting that the continental crust in the western Shandong Province witnessed horizontal plate movements at ~2.5 Ga. The metasediments and leucosomes in the Qixingtai area display regional upper amphibolite facies metamorphism and anatexis at 2.53-2.50 Ga, coeval with formation of large volumes of crustally-derived granites. These tectono-thermal events suggest that a unified continental crust was formed in the western Shandong Province at the end of Neoarchean.

Abrasivity database of different genetic rocks based on CERCHAR Abrasivity Test

“…The rock samples were obtained from open-pit mines within 100 m of the surface. Geological information on each of the mining areas can be found in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35][36] .…”

Petrogenesis and Tectonic Implications of Early Paleozoic Magmatism in Awen Gold District, South Section of the Truong Son Orogenic Belt, Laos

“…The initial Sr and Nd isotopic ratios for all these samples were calculated using their crystallized ages. The two-stage Nd mode age (T DM2 ) can correct the calculation error of the Nd mode age caused by the variation of the Sm/Nd value so that the T DM2 relative to the one-stage model ages can better reflect the time when the original magma was differentiated from the mantle reservoir [32,33]. The olivine-basalt displays higher initial 87 Sr/ 86 Sr ratios (( 87 Sr/ 86 Sr)i) (0.7113-0.7119) and negative εNd(t) values (−4.1 to −2.0), with T DM2 varying from 1.40 to 1.57 Ga.…”