阿尔泰伟晶岩中流体熔融包裹体成分的研究

对阿尔泰可可托海、柯鲁木特和库威伟晶岩锂辉石及绿柱石中单个流体熔融包裹体各相成分，借助激光拉曼探针进行分析，鉴定出固体相为不同硅酸盐子晶矿物，定量给出了流体相成分。根据子晶矿物和流体相成分估算了整个流体熔融包裹体的成分，并据此进一步讨论了熔体中流体的溶解度问题。流体熔融包裹体成分研究表明熔体中流体已达饱和或过饱和，流体相与熔体相发生分离，相应残余伟晶岩浆体系进入晶体＋熔体＋流体三相共存的岩浆－热液     

Paleo- and Mesoarchean TTG-sanukitoid to high-K granite cycles in the southern São Francisco craton,SE Brazil

The generation of the continental crust is widely accepted to have taken place predominantly in the Archean, when TTG magmatism associated with greenstone-belt supracrustal succession development was typically followed by emplacement of high-K granites before crustal stabilization. This study focuses on the Campos Gerais complex (CGC), which is an Archean granite-greenstone belt lithological association in a tectonic window located in the southwesternmost portion of the São Francisco craton (SFC). The CGC is an important segment of Paleo- to Mesoarchean continental crust to be integrated into paleogeographic reconstructions prior to the transition into the Paleoproterozoic. This investigation reports field relationships, 28 major and trace element compositions, U–Pb (zircon) geochronological results, and Hf and Sm–Nd isotope data for orthogneiss and amphibolite samples. The results indicate that the CGC records a complex Archean crustal evolution, where voluminous 2.97 Ga TTG tonalites and trondhjemites (ε_Nd(t) =  ? 4.7; T_DM = 3.24 Ga) were followed by 2.89 Ga sanukitoid tonalite production (ε_Nd(t) =  ? 1.9; T_DM = 3.02 Ga), broadly coeval with the development of the Fortaleza de Minas and Pitangui greenstone-belts. These events are interpreted to represent the initial stage of an important subduction-accretion tectonic cycle, which ended with the emplacement of 2.82–2.81 Ga high-K leucogranites and migmatization of the TTG-sanukitoid crust, with hybrid and two-mica, peraluminous compositions (ε_Nd(t) =  ? 8.0 to ? 8.6; T_DM = 3.57 – 3.34 Ga). The presence of inherited zircons with ²⁰⁷Pb/²⁰⁶Pb ages of 3.08 Ga, 3.29 Ga, 3.55 Ga and 3.62 Ga indicates that the Mesoarchean tectonic processes involved reworking of Meso- to Eo-archean crust. Renewed TTG magmatism took place at ca. 2.77 Ga represented by juvenile tonalite stocks (ε_Nd(t) = +1.0 to ? 1.5; T_DM = 2.80 – 2.88 Ga) which intrude the TTG-greenstone belt association. Crustal stabilization was attained by 2.67 Ga, allowing for the emplacement of within-plate tholeiitic amphibolites (ε_Nd(t) =  ? 3.1; T_DM = 2.87 Ga). The CGC shows important tectonic diachronism with respect to other Archean terrains in the southern São Francisco craton, including an independent Meso- to Neoarchean crustal evolution.