Age and magnetic fabric of the Trs Crregos granite batholith: evidence for Ediacaran transtension in the Ribeira Belt (SE Brazil)

作者：Salazar Carlos A; Archanjo Carlos J^*; Rodrigues Sergio W de O; Hollanda Maria Helena B M; Liu Dunyi

来源：International Journal of Earth Sciences, 2013, 102(6): 1563-1581.

DOI：10.1007/s00531-013-0908-2

• Anisotropy of magnetic susceptibility
• U-Pb zircon geochronology
• Granite
• Ribeira belt
• SE Brazil

Anisotropy of magnetic susceptibility (AMS) and U-Pb (SHRIMP) zircon ages in the eastern part of the Trs Crregos batholith (Ribeira belt, SE Brazil) indicate a well-defined fabric pattern acquired between 600 and 595 Ma. The batholith consists mostly of porphyritic granites distributed in the Ribeiro Branco, Barra do Chap,u and Itaca plutons. Late fluorite-bearing alkaline granites, some containing Sn-polymetallic greisen-type deposits, intruded the Ribeiro Branco pluton and the low-grade metasedimentary host rocks. The magnetic fabric of the Ribeiro Branco granite is dominantly oblate and oblique to the pluton elongation while that in Barra do Chap,u is mostly concentric. On both plutons, AMS records the preferred orientation of coarse, homogeneous Ti-poor magnetite grains. Such fabric patterns indicate a partitioned strain field dominated by strike-slip left-lateral shear deformation in the Ribeiro Branco and extension in the Barra do Chap,u pluton. The zircon ages of these plutons are 600 +/- A 6 Ma and 595 +/- A 4 Ma. Likewise, the ages of alkaline plutons were in the range of 597 and 595 Ma, registering a fast transition between the typical syntectonic batholithic magmatism to the late, highly evolved and specialized magmas. These results indicate that the Ribeira belt was deformed by transtension in the Middle Ediacaran. The geological setting is consistent with a continental arc with the Trs Crregos batholith emplacing at the middle-upper crust.

• 出版日期2013-9
• 单位中国地质科学院