The Naore village, Shuang’an Town in the Ziyang County, southern Shaanxi, is one of the few known selenium (Se)-enriched areas in China, and in these locations, the early cases of human Se poisoning were recorded in the 1980’s (Cheng & Mei 1980). However, the Se-rich soils stimulated agriculture production in the Naore area, which resulted in the name “Chinese Selenium Valley” (Tian 2017). The Se source in soil is attributed to pyrite-bearing and Se-enriched tuffs and carbonaceous rocks of Lower Cambrian Lujiaping Formation (Luo et al. 2004). In Naore, pyrite commonly occurs in these Se-enriched rocks that have been identified as the main source of Se (Tian et al. 2016a, b), similar to the western San Joaquin Valley of California, USA (Wu et al. 2000). For geochemical exploration, the accumulation and distribution of trace elements in the pyrite is controlled by its sedimentary process and formation environment, which are significant for understanding the possible origin and forming mechanism of the Se enrichment in Lujiaping Formation.