Affiliation:
1. China Earthquake Administration
2. Jilin Earthquake Agency
Abstract
Abstract
This study analyzes apatite via laser ablation multicollector inductively coupled plasma mass spectrometry (LA–MC–ICP–MS) and zircon via LA–ICP–MS to collect U–Pb geochronological data, alkaline feldspar and plagioclase via Rb–Sr isotope chronology and an apatite geochemistry archive for exposed Naitoushan basalt and Heishigou dike in the Changbaishan Tianchi volcano (CTV). These data are used to examine their petrogenesis and to determine the basaltic magmatism origin in CTV. The Naitoushan basalt and Heishigou dike were formed at 22.2–18.7 and 0.230–0.218 Ma, respectively. In situ oxide, volatiles, trace element geochemistry and Sr–Nd isotopes of apatite are provided for two samples. Most apatites occur as an early crystallizing phase forming inclusions in plagioclase and are euhedral or subhedral. They have higher MgO and K2O/Na2O concentrations with lower F and Cl concentrations, Ba, Sr, Nb, Ta, Zr, Hf, K, and Ti depletions, and Th, U, Ce, Pb, P, and Nd enrichments. All apatite samples have enrichment in light rare earth elements (REEs) relative to heavy REEs and relatively homogeneous ratios of Th/U, Zr/Hf, La/Sm, Nd/Tb and Sr–Nd isotopic compositions; thus, their host magmas potentially have the same magmatic origin as oceanic island basalt. The La, Yb, and U contents, the Eu/Eu* and La/Yb values, and the high REE contents in the apatites show a weak crystallization sequence in mafic magma. Combined with previous whole-rock geochemical data, apatite trace element and REE patterns and compositional variations in the rocks are controlled by the crystallization of olivine, pyroxene, plagioclase, and cocrystallizing accessory minerals. This study demonstrates that the pre–shield and post–shield mafic magmas in the CTV were likely derived from an enriched mantle source with a signature of enriched mantle I-type.
Publisher
Research Square Platform LLC