Hydrothermal Activity in the Guaymas Basin, Gulf of California: A Synthesis

Abstract

Observations of the phys. properties of sediments, the chem. of interstitial waters and solid phases, the mineralogy of the sediments, and the isotope geochem. of interstitial waters and sediments showed that 2 types of hydrothermal systems are operative in the Guaymas Basin of the Gulf of California. These include: (1) hydrothermal activity assocd. with relatively shallow basaltic sill intrusions in highly porous sediments, generally of relatively short duration and assocd. with temps. <200 Deg and (2) hydrothermal activity caused by large magmatic intrusions at greater depths. This latter activity involves recharge of the hydrothermal system by basin bottom waters; fractures in low-porosity sediments and faults in the sea floor serve as conduits for fluids heated to >300 Deg. This type of hydrothermal activity lasts long enough to lead to substantial alteration of sediments into a well-developed greenschist facies: chlorite-quartz-albite-sphene-epidote-Fe-sulfides. The mechanisms of the hydrothermal systems are discussed and are consistent with the extensive heat flow data obtained in this area. [on SciFinder (R)]