Magmatic hydrothermal fluid genesis of zeolite in the Paleogene Kongdian Formation of Zaoyuan oilfield, Bohai Bay Basin, China

HAN Guomeng,WANG Li,XIAO Dunqing,LOU Da,XU Muyue,ZHAO Yonggang,PEI Yanlu,GUO Xiaowen,TENG Jiancheng,HAN Yuanjia

Fig. 3. Micrographs of veins in Kong 2 Member mudstone samples from Well Z56. (a) Calcite with cloudy inclusions filling in the contraction cracks of bitumen, plane polarized light; (b) Calcite characterized by polysynthetic twinning, cross polarized light; (c) Gray-green scaly chlorite in contraction cracks of bitumen, plane polarized light; (d) “Rusty” anomalous interference color of chlorite, cross polarized light; (e) The growth sequence and distribution characteristics of bitumen, chlorite and barite, plane polarized light; (f) Radial chlorite associated with bitumen, two groups of nearly vertical joint in barite, plane polarized light; (g) Natrolite and calcite in the central of the fracture, and occasional residual barite crystals, columnar natrolite shows yellow-white interference color of first-order, cross polarized light; (h) Natrolite, barite and calcite in the central of the fracture, plane polarized light; (i) Early stage natrolite crystals with secondary dissolution pores cemented by later calcite, cross polarized light; (j) Analcime joint veins cut down by slip deformation parallel to the direction of mudstone laminae, fibrous chlorite crystal clusters grow vertically along the lamina, the chlorite showing yellow to brown-yellow colors, plane polarized light; (k) Chlorite in mudstone matrix showing gray-white interference color of first order, while the interference color of analcime is completely extinction, cross polarized light; (l) Laminar analcime in mudstone matrix, with complete extinction of interference color, cross polarized light. Ana—Analcime; Bar—Barite; Bit—Bitumen; Cal—Calcite; Chl—Chlorite; Layer—Mudstone layer; Nat—Natrolite; Py—Pyrite.