鄂尔多斯盆地奥陶系马家沟组白云石有序度研究

RESEARCH ON THE ORDER DEGREE OF DOLOMITE OF ORDOVICIAN MAJIA GOU GROUP IN ORDOS BASIN

在鄂尔多斯盆地奥陶系碳酸盐岩的X射线衍射、包裹体测温、薄片分析等资料的基础上,讨论了影响马家沟组白云石有序度的因素,以及与各因素间的关系。研究表明:白云石化越彻底,白云石有序度越好;白云石结晶程度好,晶形较粗大的白云石有序度好于泥晶、泥微晶白云石;CaCO3摩尔分数越接近理想摩尔分数50%,白云石有序度就越高;Fe2+、Mn2+离子的增多使白云石有序度则明显降低;相对较高温度条件下形成的白云石有序度好于相对低温条件下形成的白云石;从云化机制而论,准同生白云石化形成的白云石有序度最低,次之为渗透回流白云石化形成的白云石有序度,混合白云石化形成的白云岩中白云石有序度较好,埋藏白云石化形成的白云岩中白云石有序度最好。

This paper refers to the data records of X-RAY diffraction,fluid inclusion analysis,thin section analysis,to discuss the factors of the order degree of dolomite of Ordovician Majiagou Group.The research indicates,the dolomitization more thorough,the order degree of dolomite better;as the crystal shape better and crystal size increase,the order degree of dolomite is better than muddy-limestone.CaCO3 mole fraction is more near ideal mole fraction,the order degree is higher.As the increase of Fe2+,Mn2+,the order degree of dolomite decreases.The order degree of dolomite formed in higher temperature is better than that in the lower temperature.From the dolomitazition mechanism to disucss the order degree of dolomite,dolostones formed from paracontemporaneous is the lowest;formed from the seepage-reflux dolomitazition is lower;formed from dorag dolomitization is better;formed from burial dolomitization is the best.