(Table 2) Chemical composition of gases in basalts from DSDP Leg 65 Holes

Basalts from different structural provinces in the ocean basins, such as mid-ocean ridges, island arcs, and oceanic plateaus, show marked differences in major and minor element composition stemming from differences in magma source. In addition, there are variations even within individual provinces, based on such processes as crystal fractionation, secondary alteration, and hydrothermal alteration. It is also known that hydrothermal processes can cause changes in the gas composition of submarine basalts. For example, Zolotarev et al. (1978) have established that hydrothermal alteration frequently causes an increase in the CO2 content of basalts. If the homogeneity in composition and concentration of organic gases in oceanic basalts is associated with degassing during epimagmatic alteration, it would be interesting to investigate the relative abundance of gas phases in young basalts from midoceanic ridges.
This chapter deals with the distribution of organic gases and CO2 in young basalts recovered on Leg 65 from the Gulf of California. Our aim was to establish the relationship between gas composition and degree of alteration.

大洋盆地内不同构造省（如洋中脊、岛弧及大洋高原）的玄武岩，因岩浆源区差异，其主量与微量元素组成存在显著分异。此外，即便在单一构造省内，也会因晶体分异、次生蚀变及热液蚀变等作用过程出现成分变化。已知热液作用会改变海底玄武岩的气体组分，例如佐洛塔廖夫等人（Zolotarev et al.，1978）证实，热液蚀变通常会提升玄武岩的二氧化碳（CO₂）含量。若洋底玄武岩中有机气体的成分与浓度均一性与岩浆期后蚀变过程中的脱气作用相关，那么对洋中脊年轻玄武岩内气相的相对丰度开展研究将颇具意义。
本章聚焦加利福尼亚湾第65航次（Leg 65）采获的年轻玄武岩中有机气体与二氧化碳（CO₂）的分布特征，本研究旨在明确气体组分与蚀变程度之间的关联。