(Table 1) Downhole variation of potassium, apparent K-Ar age, and inert gas abundances at DSDP Holes 69-504B, 70-504B and 83-504B

Ne, Ar, Kr, Xe, and K2O were measured in representative samples of holocrystalline basalt from DSDP Hole 504B. No hiatus in inert gas abundance is recognized at the base of the "oxic" alteration zone and the extent rather than the nature of alteration appears to determine these abundances. When the inert gas abundances are separately plotted against K2O, two distinct trends of loss emerge, one for alteration involving K-gain, the other for K-loss. Apparent whole-rock K-Ar ages are anomalous in the upper 50 m of basement, and below 300 m sub-basement. In the intervening zone of basement, celadonization adds sufficient potassium and eliminates enough "primary" 40Ar early in the history of the basalts for "excess" 40Ar to become subordinate to radiogenic 40Ar in basalts showing potassium enrichment greater than 0.2%. Stratigraphically correct K-Ar ages are obtained, therefore, from K-enriched basalts of the oxic alteration zone.氖（Ne）、氩（Ar）、氪（Kr）、氙（Xe）以及氧化钾（K₂O）在取自深海钻探计划（Deep Sea Drilling Project, DSDP）504B孔的代表性全晶质玄武岩（holocrystalline basalt）样品中完成了含量测定。在氧化蚀变带（oxic alteration zone）的底部未观测到惰性气体（inert gas）丰度的间断现象，惰性气体丰度的主控因素实为蚀变作用的程度，而非蚀变作用的本质。当将惰性气体丰度分别与氧化钾（K₂O）含量进行关联作图时，可观察到两类截然不同的惰性气体亏损趋势：一类对应伴随钾富集的蚀变作用，另一类对应伴随钾亏损的蚀变作用。 全岩（whole-rock）表观钾氩（K-Ar）年龄在基底上部50米以及亚基底（sub-basement）下方300米的区域内呈现异常。在基底的中间过渡区段，绿纤石化（celadonization）会在玄武岩演化早期引入足量的钾，并移除足够量的“原生”⁴⁰Ar，使得当玄武岩的钾富集程度超过0.2%时，“过剩”⁴⁰Ar的占比会低于放射成因⁴⁰Ar（radiogenic ⁴⁰Ar）。因此，从氧化蚀变带内的富钾玄武岩样品中，可获得符合地层学校正要求的钾氩年龄。