Abstract

The Taihua metamorphic complex exposes in the southern Trans-North China Orogen (TNCO) and records at least three episodes of magmatism. The Shanxian TTG gneisses obtained at 2.54–2.48Ga have high SiO2, variable Mg# with high (La/Yb)N and Sr/Y ratios (15.08–93.26 with average of 37.31 and 7.33–115.05 with average of 49.59, respectively). They show negative Nb and Ta but positive Zr and Hf anomalies with low Nb/Ta and Gd/Yb, and high Zr/Hf and Zr/Sm ratios (4.97–18.8, 1.92–6.37, 23.71–50.26, and 29.18–75.23, respectively), and have positive εHf (t) values (+1.7 to +7.9) and εNd(t) values (+0.72 to +2.55), indicating that they were possibly produced by partial melting of lower crust derived from metasomatized lithospheric mantle with the residue of minor garnet. The Sihe granitic gneisses recorded at 2.35–2.30Ga are enriched in silica, Al2O3 contents (13.59–15.33), K2O/Na2O ratios (1.13–1.7), defined as high-Al TTG. They exhibit high Sr/Y, Zr/Sm and Zr/Hf ratios and low Nb/Ta and Gd/Yb ratios (44.71–83.09, 47.79–62.58, 36.05–37.43, 12.04–16.36, and 2.95–3.68, respectively) with negative Eu anomaly. Combined with Hf and Nd isotopes (−2.5 to +4.7 and −0.74 to +0.36), the Sihe granitic gneiss was possibly generated from partial melting of lower crust with minor ancient material contributions, leaving residual amphibole and minor garnet in the source. The Muce monzonitic gneisses emplaced at 2.17–2.16Ga have high Mg#, Ni and Cr contents, constant Sr/Y and (La/Yb)N (42.39–50.33, 19.8–41.4, 33.6–74.2, 31.32–34.14, and 15.32–16.7, respectively), with relatively low and constant Dy/Yb ratio (1.82–1.85). Together with Hf and Nd isotopes (−6.5 to −0.9 and −2.07 to −2.86), the Muce monzonitic gneisses might be derived from partial melting of Neoarchean pre-existing crustal materials, possibly in an arc setting. It is therefore found that four episodes of crustal growth and/or reworking in the southern segment of the TNCO have occurred at 2.85–2.72Ga, 2.57–2.48Ga, 2.35–2.30Ga and 2.2–2.0Ga, respectively, likely to connect with the subduction–collision between the Eastern and Western Blocks along the TNCO in the North China Craton.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.