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安徽金寨三仙山地区位于大别山北缘,该地梅山群主要为一套轻微变质的碎屑岩系。砂岩碎屑组分统计表明,砂岩类型主要为岩屑石英砂岩、岩屑石英杂砂岩,石英、长石、岩屑的平均含量为87.21%、1.67%、9.64%,杂基含量为15%;石英几乎全为单晶石英(95.79%),长石以斜长石为主,岩屑主要为沉积岩屑(75.49%),其次为变质岩屑(24.51%)。碎屑岩地球化学元素平均含量为:SiO_2(75.99%),Al_2O_3(11.96%),MgO(0.72%),CaO(0.10%),Fe_2O_3(4.02%),K_2O(1.70%),Na_2O(0.26%)。∑REE=170.49×10~(-6)(74.49×10~(-6)~309.42×10~(-6)),LREE/HREE=11.16(7.89~14.26),轻稀土略有富集,δEu=0.72(0.59~0.90),La/Yb=22.08(13.01~31.18),(La/Yb)_N=14.89(8.77~21.02),δCe=0.84(0.42~0.97)。碎屑岩地球化学特征指示三仙山地区梅山群母岩主要为古老沉积岩、长英质火山岩和古老变质基底,具有多重物源区。梅山群构造背景较复杂,主要为被动大陆边缘和活动大陆边缘,其次为大陆岛弧。三仙山地区梅山群碎屑岩的源岩成分、构造背景与商城—固始地区石炭系有很大差别,故其地层时代有待于进一步研究。
Sanxian Mountain in Jinzhai, Anhui Province is located in the northern margin of the Dabie Mountains. The Meishan Group in this area is mainly composed of a slightly altered clastic series. The statistics of the clastic components of sandstone show that the sandstone types are mainly composed of lithic quartz sandstone, lithic quartz sandstone, quartz, feldspar and debris with the average content of 87.21%, 1.67% and 9.64% and the content of miscellaneous group of 15%. Quartz almost all single crystal quartz (95.79%), feldspar mainly plagioclase, rock fragments are mainly sedimentary debris (75.49%), followed by metamorphic debris (24.51%). The average content of geochemical elements in clastic rocks is as follows: SiO 2 (75.99%), Al 2 O 3 (11.96%), MgO 0.72%, CaO 0.10%, Fe 2 O 3 4.02%, K 2 O 1.70%, Na 2 O 0.26% ). LREE / HREE = 11.16 (7.89 ~ 14.26), slightly enriched in light rare earths, and δEu (ΣREE = 170.49 × 10 -6) (74.49 × 10 -6 ~ 309.42 × 10 -6) = 0.72 (0.59-0.90), La / Yb = 22.08 (13.01-31.18), (La / Yb) _N = 14.89 (8.77-21.02), and δCe = 0.84 (0.42-0.97). The geochemical characteristics of clastic rocks indicate that the Meishan Group rocks in the Sanxian Mountain area are mainly composed of ancient sedimentary rocks, long quartzitic volcanic rocks and ancient metamorphic basalts with multiple provenance zones. Meishan Group tectonic setting is more complicated, mainly passive continental margin and active continental margin, followed by continental island arc. The source rock composition and tectonic setting of the Meishan Group clastic rock in the Sanxian Mountain area are quite different from that of the Carboniferous in the Shangcheng-Gushi area, so the stratigraphic age needs further study.