Rb-Sr Geochronology and Geochemical Characteristics of Mafic Dikes in the Nova Lacerda and Conquista D´Oeste Region, Mato Grosso, SW Amazonian Craton

• Main Authors: Amarildo Salina Ruiz, Vicente Antonio Vitório Girardi, João Batista de Matos, Paulo César Corrêa da Costa
• Format: Article
• Language: English
• Published: Universidade de São Paulo 2009-01-01
• Series: Geologia USP. Série Científica
• Subjects: Mafic dikes; Geochemistry; Geochronology; Amazonian craton.
• Online Access: http://ppegeo-local.igc.usp.br/pdf/guspsc/v9n1/v9n1a08.pdf

In the Nova Lacerda and Conquista D’Oeste regions, Mato Grosso State, SW part of the Amazonian Craton, mafi c dikestrending NNW intrude the Nova Lacerda Granite (1462 ± 12 Ma), within the Jauru Domain, in the Rondonia-San IgnacioProvince (1.55 - 1.3 Ga). The mafi c swarm comprises diabases, metadiabases and amphibolites. Metadiabases originatedfrom uralitization of diabases. These rocks have tholeiitic affi nity and predominant basaltic composition. Some samples are andesi-basalts. The ages of diabases and metabasites are 1380 ± 32 Ma and 1330 ± 120 Ma respectively. Geochemical data indicate that the compositional variation of diabases and metadiadases is due to fractional crystallization of evolved tholeiitic magmas. The origin of the basaltic magmas is related to a heterogeneous mantle source.