(Table 1) Physical properties of basalts from DSDP Legs 69 and 70

Physical properties of basalts from Deep Sea Drilling Project Sites 504 and 505, south of the Costa Rica Rift, including wet-bulk density, water content, sonic velocity, and thermal conductivity, were measured on board D/V Glomar Challenger during Legs 69 and 70. The mean wet-bulk density is 2.90±0.06 g/cm**3, porosity 5.0±2.2%, sonic velocity 5.75±0.30 km/s, and thermal conductivity 1.67±0.09 W/m°K.
Basalts from this young ocean crust (5.9 m.y.) have relatively low porosity and consequently high density and sonic velocity, as compared to average DSDP basalts.
Some systematic trends in depth variation of physical properties were found: down to Core 40 in Hole 504B, grain densities were lower than those deeper in the hole, whereas porosity in the upper section was higher. This can be attributed either to differences in the flow type or in the nature of alteration of basalts at the different levels in the hole.

深海钻探计划（Deep Sea Drilling Project, DSDP）哥斯达黎加裂谷南侧504与505站位的玄武岩物性参数，包括湿体积密度（wet-bulk density）、含水量、声速（sonic velocity）与热导率（thermal conductivity），已于“格洛玛·挑战者”号（D/V Glomar Challenger）第69、70航次期间完成船上测定。其平均湿体积密度为2.90±0.06 g/cm³，孔隙度为5.0±2.2%，声速为5.75±0.30 km/s，热导率为1.67±0.09 W/(m·K)。这套形成于5.9百万年的年轻洋壳玄武岩，相较于深海钻探计划的常规玄武岩样品，孔隙度相对偏低，因此具备更高的体积密度与声速。研究发现物性参数随深度变化存在系统性规律：在504B钻孔的第40岩芯以浅区段，玄武岩的颗粒密度低于钻孔深部样品，而浅部区段的孔隙度则更高。该现象可归因于钻孔不同深度处玄武岩的喷发流动类型差异，或是蚀变作用特征的不同。