鄂尔多斯盆地奥陶系马家沟组五段富铁白云石成因
发布时间：2019-01-03 09:03
【摘要】：鄂尔多斯盆地马家沟组五段白云岩,按照晶粒可分为两种类型:晶粒较细的M型微晶白云岩和晶粒相对较粗的F型粉细晶白云岩。这两类白云岩都具有较高的Fe含量,但Fe并不是均一分布的。在M型微晶白云岩中,基质白云石的铁含量为583×10~(-6)~3 811×10~(-6),富铁白云石主要以膏溶铸模孔的孔隙充填物的形式存在,粗晶白云石充填物铁含量29 112×10~(-6)~47 148×10~(-6),均匀分布于晶体之中;而粉晶白云石充填物,铁含量最可达81 752×10~(-6),仅富集于白云石的边缘。在F型粉-细晶白云岩中,其基质白云石的铁含量为233×10~(-6)~2 007×10~(-6);裂缝和孔隙内充填的白云石的铁含量较高,可达9 178×10~(-6),均匀分布。铁的富集可能与孔隙的发育有一定联系。孔隙越发育,容易富集铁。M型微晶白云石的δ~(13)C(V-PDB)值为-3.5‰~1.4‰,δ~(18)O(V-PDB)值为-6.5‰~-8.0‰;孔隙充填物粉晶白云石δ~(13)C(V-PDB)值为-0.7‰~-2.7‰,δ~(18)O(V-PDB)值在-9.8‰~-11.5‰;粗晶白云石的δ~(13)C(V-PDB)值范围为-1.7‰~-2.9‰,δ~(18)O(V-PDB)值范围为-9.9‰~-11.3‰,可能受到过较高温度流体的影响。F型粉细晶白云岩的δ~(13)C(V-PDB)值为-0.4‰~-0.8‰,δ~(18)O(V-PDB)值为-5.3‰~-6.6‰,与海水较为接近。两类白云岩的Fe可能来源于上覆的铁质粘土岩。白云岩形成后,后经历了漫长的风化暴露剥蚀,形成了大量的储集空间,并残存形成了上覆铁质粘土岩。当再次进入埋藏期后,铁质粘土岩中富铁的流体在重力的作用下,向下部的地层运移,且到一定深度时,氧化态Fe3+转化为还原态的Fe2+,且已具有相对较高的地温,使得Fe2+更容易进入白云石晶格,形成了富铁的白云岩层系。
[Abstract]:There are two types of dolomite in the fifth member of Majiagou formation, Ordos Basin: M type fine dolomite with fine grain size and F type fine grain dolomite with relatively coarse grain. Both types of dolomite have high Fe content, but Fe is not uniformly distributed. In M-type microcrystalline dolomite, the iron content of matrix dolomite is 583 脳 10 ~ (-6) ~ 3 811 脳 10 ~ (-6). The iron content of coarse dolomite filling is 29 112 脳 10 ~ (-6) ~ 47 148 脳 10 ~ (-6), which distributes uniformly in the crystal. However, the iron content of powdered dolomite filling is 81,752 脳 10 ~ (-6), which is only concentrated on the edge of dolomite. The iron content of dolomite matrix is 233 脳 10 ~ (-6) ~ 2 007 脳 10 ~ (-6) in F-type powder-fine-grained dolomite, and the iron content of dolomite filled in fractures and pores is high, up to 9 178 脳 10 ~ (-6). The enrichment of iron may be related to the development of pores. The microcrystalline dolomite of M type has 未 ~ (13) C (V-PDB) values of -3.5 鈥，
本文编号：2399169
[Abstract]:There are two types of dolomite in the fifth member of Majiagou formation, Ordos Basin: M type fine dolomite with fine grain size and F type fine grain dolomite with relatively coarse grain. Both types of dolomite have high Fe content, but Fe is not uniformly distributed. In M-type microcrystalline dolomite, the iron content of matrix dolomite is 583 脳 10 ~ (-6) ~ 3 811 脳 10 ~ (-6). The iron content of coarse dolomite filling is 29 112 脳 10 ~ (-6) ~ 47 148 脳 10 ~ (-6), which distributes uniformly in the crystal. However, the iron content of powdered dolomite filling is 81,752 脳 10 ~ (-6), which is only concentrated on the edge of dolomite. The iron content of dolomite matrix is 233 脳 10 ~ (-6) ~ 2 007 脳 10 ~ (-6) in F-type powder-fine-grained dolomite, and the iron content of dolomite filled in fractures and pores is high, up to 9 178 脳 10 ~ (-6). The enrichment of iron may be related to the development of pores. The microcrystalline dolomite of M type has 未 ~ (13) C (V-PDB) values of -3.5 鈥，
本文编号：2399169
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