Characteristics and origin of Lower Triassic Feixianguan Formation dolostones on the west side of Kaijiang–Liangping Trough, northeastern Sichuan Basin, China
Characteristics and origin of Lower Triassic Feixianguan Formation dolostones on the west side of Kaijiang–Liangping Trough, northeastern Sichuan Basin, China
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川东北开江—梁平海槽西侧下三叠统飞仙关组白云岩特征及成因
DOI：
10.1016/j.marpetgeo.2022.105956
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发表时间：
2022-10
影响因子：
4.2
通讯作者：
Ping Wang
中科院分区：
文献类型：
--
作者：
Ling Zhou;Guangwei Wang;Ya Zhang;Yanping Qiao;Fang Hao;Rui Xu;Li Quan;Ping Wang
川东北飞仙关组优质储层以白云岩为主，含天然气丰富。它们的成因存在争议，这阻碍了这些优质碳酸盐岩储层的勘探。通过对飞仙关白云岩中各种碳酸盐岩的岩相学观察和地球化学分析，探讨了成岩流体的来源，阐明了飞仙关白云岩的形成机制。根据白云岩的粒度可将白云岩分为细白云岩、细-中白云岩和中白云岩三种类型。细白云石的特征是晶体尺寸为5-60 μm，稀土元素总量（REE）为1.87-2.45 ppm。薄层细白云岩主要出现在沉积旋回的顶部，其δ 18 O值最高，SmSN/YbSN值最低，为0.65-0.87，表明它们是由有限蒸发海水的蒸发泵蚀作用形成的。细-中白云石具有继承原始颗粒结构的特征，晶体尺寸为60-120 μm。中等白云岩的晶体粒度为100-200 μm，孔隙度最高。细-中、中辉长岩的稀土元素组成与海水相似，87 Sr/86 Sr比值与飞仙关海水相同，表明辉长岩化流体来源于与飞仙关灰岩同时代的海水。高Na含量和低Fe、Mn含量均反映了白云石化的浅埋或近地表条件。根据δ 13 C和δ 18 O值高于同时代灰岩，以及δ 18 O值和Na浓度从沉积旋回的顶部到底部呈下降趋势，细-中-中灰岩是由海滩桥限制下蒸发的飞仙关海水回流石化形成的。中等白云石的阴极发光强度略高于细-中等白云石，δ 18 O值随晶体粒度的增大而减小，说明中等白云石是由细-中等白云石轻微重结晶而成。此外，孔隙中的少量粗粒碳酸盐岩来自埋藏环境中的外源非海水流体。
High-quality reservoirs of the Feixianguan Formation of the northeast Sichuan Basin contain abundant natural gas and are dominated by dolostones. Their origin is controversial, which impedes the exploration of these high-quality carbonate reservoirs. Petrographic observation and geochemical analysis were performed on various carbonates to trace the source of dolomitizing fluids and clarify the formation mechanism of the Feixianguan dolostones. Three types of dolostones were distinguished, including fine dolomite, fine-medium dolomite, and medium dolomite according to the grain size of dolomites. Fine dolomite was characterized by crystal sizes of 5–60 μm and high total rare earth elements (ΣREEs) of 1.87–2.45 ppm. The thin layers of fine dolomite mainly occur at the top of the depositional cycles and have the highest δ18O values and the lowest SmSN/YbSNvalues of 0.65–0.87 of the three types, suggesting that they were formed by evaporation pumping dolomitization from the restricted evaporated seawater. Fine-medium dolomite was characterized by the inheritance of the original particle texture with crystal sizes of 60–120 μm. Medium dolomite was characterized by crystal sizes of 100–200 μm and the highest porosity among the three types of dolostones. The similar REE patterns to seawater and the same87Sr/86Sr ratios as Feixianguan seawater for fine-medium and medium dolomites indicate that the dolomitizing fluids originated from coeval seawater with the Feixianguan limestone. Both the high concentrations of Na and low concentrations of Fe and Mn imply the shallow burial or near surface condition of dolomitization. According to higher δ13C and δ18O values than coeval limestones, and the descending tendency of δ18O values and Na concentrations from the top to bottom of the sedimentary cycles, fine-medium and medium dolomites were formed by reflux dolomitization of evaporated Feixianguan seawater restricted by beach bridges. However, slightly brighter cathodoluminescence of medium dolomite than fine-medium dolomite and the decreasing of δ18O values as the crystal size increasing imply that medium dolomites were slightly recrystallized from fine-medium dolomites. Moreover, a small number of coarse dolomites in pores are derived from exogenous non-seawater fluids in the burial environment.
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影响因子：
3.9
作者：
Gao, Shan;Zhou, Lian;Hu, Zhaochu;Liu, Yongsheng
通讯作者：
Liu, Yongsheng
影响因子：
3.8
作者：
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影响因子：
12.1
作者：
J. Warren
通讯作者：
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影响因子：
2.8
作者：
J. Sarg
通讯作者：
J. Sarg
DOI：
10.1016/c2010-0-65780-4
发表时间：
2013-10
期刊：
--
影响因子：
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作者：
C. Moore;W. J. Wade
通讯作者：
C. Moore;W. J. Wade