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自生黏土矿物形成过程是个备受关注的科学问题,查明该过程对于盆地热史分析至关重要。本次研究以北部湾盆地福山凹陷岩浆侵入体附近的沉积砂岩为研究对象,使用离心机分离出不同粒度的自生黏土矿物,并对其进行系统的矿物学、Rb-Sr年代学及~(40)Ar-~(39)Ar年代学研究。结果表明,粗砂岩中自生黏土矿物富集且纯度很高,是开展年代学分析的理想对象;Rb-Sr等时线定年结果显示自生黏土矿物形成年代为~31 Ma,该年龄与岩浆岩U-Pb年代具有非常好的耦合关系,而~(40)Ar-~(39)Ar定年法受到“~(40)Ar丢失”的影响而缺乏地质意义。本次研究说明热事件发育地区自生黏土矿物的生长过程严格受控于短时间的岩浆岩侵入事件,而非长时间的盆地埋藏过程。
The process of authigenic clay mineral formation is a major scientific issue of concern, and it has been found that this process is crucial to the thermal history of the basin. In this study, the sedimentary sandstone near the magma intrusion in the Fukeng Sag, Beibu Gulf Basin was selected as the research object. Centrifuges were used to separate the calcareous minerals with different particle sizes. The mineralogy, Rb-Sr chronology and ~ (40) ) Ar- ~ (39) Ar Geochronology. The results show that the calcareous minerals in the coarse sandstone are enriched and have high purity, which is an ideal target for chronological analysis. The dating of Rb-Sr isochron shows that the age of authigenic clay mineral is ~ 31 Ma, which is similar to that of magmatic rocks U -Pb has a very good coupling relationship, while the ~ (40) Ar- ~ (39) Ar dating method is affected by the “~ (40) Ar loss” and lacks geologic significance. This study shows that the growth of authigenic clay minerals in developed areas of the thermal event is strictly controlled by a short period of magmatic intrusion rather than a prolonged period of basin burial.