JOPC ›› 2023, Vol. 25 ›› Issue (5): 1199-1210. doi: 10.7605/gdlxb.2023.05.076

• The 70th Anniversary Album of China University of Petroleum (Ⅰ) • Previous Articles    

Spherulite-dendritic crystal characteristics and its genesis of the Lower Cretaceous lacustrine carbonate rocks in Santos Basin,Brazil

SUN Haitao1,2, HUANG Xiaojie1,2, YANG Liu3, FAN Guozhang3, HUANG Xiaojuan1,2, WANG Hongping3, ZHONG Dakang1,2, ZHOU Siyu1,2   

  1. 1 College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;
    2 Carbonate Research Center,China University of Petroleum(Beijing),Beijing 102249,China;
    3 PetroChina Hangzhou Research Institute of Geology,Hangzhou 310023,China
  • Received:2023-03-14 Revised:2023-04-11 Online:2023-10-01 Published:2023-09-28
  • Contact: YANG Liu,born in 1986, is a senior engineer. He is mainly engaged in research on carbonate reservoir. E-mail: yanliu_cas@163.com.
  • About author:SUN Haitao,born in 1985,is an associate professor and Doctoral supervisor. He is mainly engaged in teaching and research in sedimentology and reservoir geology. E-mail: haitao.sun@cup.edu.cn.

巴西桑托斯盆地下白垩统湖相碳酸盐岩球粒—树枝状组构特征与成因*

孙海涛1,2, 黄小洁1,2, 杨柳3, 范国章3, 黄小娟1,2, 王红平3, 钟大康1,2, 周思宇1,2   

  1. 1 中国石油大学(北京)地球科学学院,北京 102249;
    2 中国石油大学(北京)碳酸盐岩研究中心,北京 102249;
    3 中国石油杭州地质研究院,浙江杭州 310023
  • 通讯作者: 杨柳, 男, 1986年生,高级工程师,主要从事碳酸盐岩沉积储层研究。 E-mail: yanliu_cas@163.com
  • 作者简介:孙海涛,男,1985年生,副教授,博士生导师,主要从事沉积学及储层地质学领域的教学与研究工作。E-mail: haitao.sun@cup.edu.cn。

Abstract: The Lower Cretaceous Barra Velha Formation in Santos Basin,Brazil,consists of lacustrine carbonate components with spherical,dendritic and shrub structures,but their origin has not been unified yet. Based on the analysis of drilling core and thin section data,combined with geochemical data and regional tectonic background,this paper analyzes the characteristics of various components,classification, and depositional environments of these carbonate rocks. The research shows that spherical crystals with cross extinction under orthogonal light developed in the Barra Velha Formation,also including fan-shaped crystals,dendriform crystals and dendritic crystals with undulatory extinction. The micritic limestone,spherical crystal and dendritic crystal formed an upper vertical sequence. Trace elements,carbon and oxygen isotopes,and clumped isotopes,suggest a high-salinity and high-temperature fluid condition when the spherulite-dendritic crystals were deposited. In combination with regional tectonic background of the Santos Basin,this paper proposes the spherical crystal-dendritic particles were caused by the hydrothermal fluid connected by the deep large faults,and the saline minerals charge supplied by the frequent seawater transgression. This model better explains the characteristics of the rapid growth of spherulite-dendritic particles,and provides a new theoretical basis for the genesis and distribution of carbonate reservoirs in this basin.

Key words: Santos Basin, Cretaceous, lacustrine carbonate rocks, spherulite, hydrothermal deposition

摘要: 巴西桑托斯盆地下白垩统Barra Velha组发育形状为球粒状、灌木状、树枝状的湖相碳酸盐结构组分,但对其成因的认识尚未统一。利用岩心、薄片资料,结合地球化学测试结果和区域构造背景,详细分析了Barra Velha组碳酸盐岩的结构组分特征、分类及其成因环境特征。研究表明: Barra Velha组发育十字消光的球粒状组构及波状消光的扇状、灌木状和树枝状组构,垂向上呈泥晶—球粒状—树枝状组构沉积序列; 微量元素、碳氧同位素及团簇同位素测试结果支持Barra Velha组球粒状—树枝状组构沉积时,水体具高盐度、高温的特点。结合区域沉积背景,提出深大断裂沟通热液导致湖水升温、表层海水频繁海侵补给盐类物质的桑托斯盆地球粒状—树枝状组构热水沉积模式。该研究成果可以较好地解释球粒状—树枝状组构快速生长的特征,也为该层系碳酸盐岩储层成因和分布规律研究提供了新的依据。

关键词: 桑托斯盆地, 白垩系, 湖相碳酸盐岩, 球粒结构, 热水沉积

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