Evolution of the mineral deposits from Långban, Sweden, as recorded from strontium isotope data

Abstract

Strontium isotope analyses of 17 low- to high-temperature minerals from the Längban ore district point to an exhalative-sedimentary origin for the ores in an active continental margin environment. The volcanogenic Sr component was continuously mixed with a sedimentary Sr component, probably derived from an Archean (> 2.5 Ga) erosional area, rich in radiogenic ⁸⁷Sr. For the later stages of mineral formation this addition of Sr caused an increase in ⁸⁷Sr/⁸⁶Sr ratios clearly different from an evolution only due to decay of ⁸⁷Rb.

Key Words:

• Långban
• strontium isotopes
• strontium minerals
• exhalative-sedimentary
• continental margin
• central Sweden