Geochemistry of intrusive rock in Dachang tin-polymetallic ore field, Guangxi, China: Implications for petrogenesis and geodynamics
(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. State Key Laboratory of Ore Deposit Geochemistry,
Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China)
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. State Key Laboratory of Ore Deposit Geochemistry,
Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China)
Abstract: The major element, trace element and rare earth element (REE) of the intrusion rock from the Dachang ore field in Guangxi, China, were analyzed. The results show that the phenocryst (about 15%) and matrix (about 85%) mainly consist of quartz, K-feldspar and plagioclase. The rock is composed of low content of Si and high content of Al2O3, low contents of Ca, Fe2O3, Na, TiO2, etc. The intrusion rock has the medium alkali content, attributing to K-rich type rock; and contains medium to low REE contents, of which light rare earth elements (LREEs) and heavy rare earth elements (HREEs) are highly fractionated, showing a weak negative Ce anomaly and a negative Eu anomaly. These rocks are enriched in LREE, and the large ion lithophytes elements (LILE) are rich in Rb, Sr, and U; the high-field-strength elements (Nb, Th, etc) are relatively depleted. The REE chondrite-normalized patterns are consistent with the overall, roughly indicating their similar characteristics, sources and evolution. The intrusion rock mainly formed during the collisional and within-plate periods.
Key words: geochemistry; petrogenesis; tectonic setting; magma evolution; Dachang ore field; Guangxi