The LA-ICP-MS zircons U-Pb ages and geochemistry of the Baihua basic igneous complexes in Tianshui area of West Qinling

Abstract

Baihua meta-igneous complex consists mainly of pyroxenite-gabbro(diorite)-diorite-quartz diorite. They form a complete comagmatic evolutionary series. The geochemical characteristics of basic-intermediate basic igneous rocks indicate that they belong to a tholeiite suite. The REE distribution pattern is nearly flat type and LREE is slightly enriched type, and their primitive mantle-normalized and MORB-normalized trace element spider diagrams are generally similar; the LIL elements (LILE) Cs, Ba, Sr, Th and U are enriched, but Rb, K and the HFSEs Nb, P, Zr, Sm, Ti and Y are relatively depleted. All these show comagmatic evolution and origin characteristics. The tectonics environment discrimination of trace element reveals that these igneous complexes formed in an island-arc setting. The LA-ICP-MS single-zircons U-Pb age of Baihua basic igneous complex is 434.6±1.5 Ma (MSWD = 1.3), which proves that the formation time of the island-arc type magmatite in the northern zone of West Qinling is Late Ordovician or Early Silurian, also reveals that the timing of subduction of paleo-ocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magmatic activities is probably Middle-Late Ordovician to Early Silurian. basic igneous complex, island-arc setting, LA-ICP-MS, zircons U-Pb isotopic ages, Tianshui area, West Qinling

Tectonic architecture and multiple orogeny of the Qinling Orogenic Belt, Central China

“…15a). These are represented by the Guanzizhen (Pei XZ et al, 2005) and Baihua (Pei XZ et al, 2007b) gabbros in the western NQT, the Houzhenzi and Sifangtai (Liu JF et al, 2008) gabbros in the middle NQT, and the Lajimiao (Li SG et al, 1993) and Fushui in the eastern NQT (Dong YP et al, 1997;Su L et al, 2004;Zhang HF et al, 2014).…”

“…In the west NQT, both Guanzizhen and Baihua show subduction-related geochemical features of significant depletion of Nb-Ta and Ti, and enrichment of Th, Pb and Sr in the mafic rocks, which yield TIMS zircon U-Pb ages of 507±3.0 Ma and 499±1.8 Ma for the Guanzizhen gabbro (Pei XZ et al, 2005), and LA-ICPMS zircon ages of 450±3.1 Ma and 434±1.5 Ma for the Baihua gabbro (Pei XZ et al, 2007b).…”

North Qinling Paleozoic granite associations and their variation in space and time: Implications for orogenic processes in the orogens of central China

“…The early intrusions (455-450 Ma) are small and the late (450 to 422 Ma) are large (up to 300-400 km 2 ) with elliptical or irregular shape. Mafic intrusions (443-434 Ma [53,56] ) also occur in this stage.…”

“…Data from refs [5,7,19,35,38,42,44,[49][50][51][52][53][54][55][56][57]. and this paper; The ages for mafic intrusion are zircon U-Pb (LA-ICP-MS, SHRIMP and TIMS) ages.…”

Mesozoic intracontinental orogeny in the Qinling Mountains, central China

“…The northward subduction of the Shangdan Ocean was indicated by the subduction-related gabbroic intrusions of ca. 507-422 Ma in the NQB (Lu et al, 2003;Su et al, 2004;Pei et al, 2005;Li et al, 2006;Liu et al, 2007;Pei et al, 2007b;Jiang et al, 2009;Liu et al, 2009) and granitic plutons in ages of ca. 514-402 Ma (Chen et al, 2008;Dong et al, 2011a and references therein;Xue et al, 1996;Li et al, 2000;Lu, 2000;Lu et al, 2003;Zhang et al, 2006;Xu et al, 2007;Wang et al, 2009).…”