TY - JOUR

T1 - Age and geochemistry of granites associated with Momineralizations in western Bergslagen, Sweden

AU - Sundblad, K.

AU - Ahl, M.

AU - Schöberg, H.

PY - 1993/12

Y1 - 1993/12

N2 - The Bergslagen area, south-central Sweden, where large amounts of Fe, Cu, Zn, Pb, Au, Ag, Mo and W have been produced for several centuries, is one of the oldest mining districts in Europe. Two episodes of magmatism and ore formation can be distinguished: (1) an "older", Early Svecofennian phase that generated 1890-1850 Ma old calc-alkaline, continental-margin volcanic and plutonic units related to the Svecofennian orogeny; and (2) a "younger" phase comprising potassiumrich granitoids, which intruded over a period extending from 1825 to 1680 Ma during the final stage of, or subsequent to, the regional metamorphism and deformation related to the Svecofennian orogeny. In recent years, considerable confusion has dominated the discussion concerning the timing and setting of the MoW-forming granites in western Bergslagen. In this study, one of the most important intrusions of undeformed granite in western Bergslagen has been investigated in regard to geochemistry and UPb zircon age. The granite (Skålhöjden) has a peraluminous, silica- and potassium-rich chemistry as well as a uniformly flat REE-pattern with a marked negative Eu anomaly. The UPb data yielded an age of 1758±8 Ma. These data show convincingly that the granite is comparable to other 1800-1680 Ma MoW-bearing granitoids elsewhere in the Fennoscandian Shield but are in strong conflict with hypotheses on Early Svecofennian rift-related crust- and ore-forming processes recently proposed for western Bergslagen. A revision of the models of crustal growth and ore formation in that area is suggested.

AB - The Bergslagen area, south-central Sweden, where large amounts of Fe, Cu, Zn, Pb, Au, Ag, Mo and W have been produced for several centuries, is one of the oldest mining districts in Europe. Two episodes of magmatism and ore formation can be distinguished: (1) an "older", Early Svecofennian phase that generated 1890-1850 Ma old calc-alkaline, continental-margin volcanic and plutonic units related to the Svecofennian orogeny; and (2) a "younger" phase comprising potassiumrich granitoids, which intruded over a period extending from 1825 to 1680 Ma during the final stage of, or subsequent to, the regional metamorphism and deformation related to the Svecofennian orogeny. In recent years, considerable confusion has dominated the discussion concerning the timing and setting of the MoW-forming granites in western Bergslagen. In this study, one of the most important intrusions of undeformed granite in western Bergslagen has been investigated in regard to geochemistry and UPb zircon age. The granite (Skålhöjden) has a peraluminous, silica- and potassium-rich chemistry as well as a uniformly flat REE-pattern with a marked negative Eu anomaly. The UPb data yielded an age of 1758±8 Ma. These data show convincingly that the granite is comparable to other 1800-1680 Ma MoW-bearing granitoids elsewhere in the Fennoscandian Shield but are in strong conflict with hypotheses on Early Svecofennian rift-related crust- and ore-forming processes recently proposed for western Bergslagen. A revision of the models of crustal growth and ore formation in that area is suggested.

UR - http://www.scopus.com/inward/record.url?scp=0027798383&partnerID=8YFLogxK

U2 - 10.1016/0301-9268(93)90085-G

DO - 10.1016/0301-9268(93)90085-G

M3 - Article

AN - SCOPUS:0027798383

VL - 64

SP - 319

EP - 335

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

IS - 1-4

ER -