Abstract: Characteristic and origin of “spherical particle” are studied based on contrast analysis of petrography and carbon and oxygen isotope of “spherical particles” in basite drawn from well and typical amygdules in basalt sampled in the field. Results show that “spherical particles” and amygdules are significantly different in microscopic and carbon and oxygen isotopic characteristics although they are similar in macroscopic feature. “Spherical particles” are characterized by non-oscillatory zoning, obvious recrystallization in the rim, and different carbon and oxygen isotopic values in different “spherical particle” of the same sample. Amygdules are characterized by oscillatory zoning, big crystalline particle, and similar carbon and oxygen isotopic values in different amygdule of the same sample. It can be concluded that “spherical particle” stems from magma capturing pieces of sedimentary carbonate, rather than secondary minerals filling vent. As a result, the basite drilled from the Cambrian and Carboniferous strata is intrusive rock, and volcanism may not occur in related strata.

Key words: “spherical particles” in basite, amygdules, carbon and oxygen isotope, Tarim Basin

摘要： 通过塔里木盆地野外采样的玄武岩典型杏仁体和钻井取芯的基性岩“球粒”的岩相学和碳、氧同位素地球化学对比分析, 对塔里木盆地基性岩“球粒”特征及成因进行了研究。综合分析表明, “球粒”和杏仁体虽然宏观特征相近, 但在微观特征和碳、氧同位素组成上具有明显的差异: “球粒”不具环带结构, 边部重结晶作用明显, 同一样品不同“球粒”的δ¹³C和δ¹⁸O相差较大; 杏仁体普遍具环带结构, 结晶颗粒较大, 同一样品不同杏仁体的δ¹³C和δ¹⁸O较为接近。岩相学特征和碳、氧同位素地球化学特征均表明基性岩中的“球粒”是岩浆捕掳沉积碳酸盐岩围岩碎块而成的, 与典型杏仁体的次生矿物充填气孔成因明显不同, 因而推测钻遇的基性岩为侵入岩, 相关层系并非一定发生过火山活动。

关键词: 基性岩“球粒”, 杏仁体, 碳, 氧同位素, 塔里木盆地