Author: Lisard Torró i AbatPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
"The Maimón and Los Ranchos formations in Central and Oriental Cordilleras, Dominican Republic, Hispaniola Island, are acknowledged to be representative of the most primitive tholeiitic magmatic series recorded in the Greater Antilles of the Caribbean. Besides their importance for the study of the early tectonic and magmatic evolution of the Caribbean island-arc, these formations are renowned for hosting the Cerro de Maimón VMS and the world-class Pueblo Viejo epithermal deposits, currently under production, and a series of smaller metallic deposits and occurrences. Therefore, the integrated study of the hosting volcanic suites, the hydrothermal alterations and the sulfide mineralization from petrographic, geochemical and geochronological perspectives stands out as an excellent opportunity to understand the metallogenic evolution associated to the early evolution of intra-oceanic subduction systems. In this Thesis, new whole rock major- and trace-element and radiogenic isotope data, detailed petrographic studies of the hosts, hydrothermal alterations and the sulfide mineralization and geochronological constraints by means of zircon U-Pb and molybdenite Re-Os dating are presented and discussed. Bottom to top, basalts and basaltic andesites of the Maimón Formation (metamorphosed in the greenschists-blueschists facies transition) and of the lower portion of the Los Ranchos Formation shift from LREE-depleted low-Ti tholeiites and boninites to LREE-richer (normal) low-Ti tholeiites. In addition, basaltic andesites, diorites, monzodiorites and andesites of the upper portion of the Los Ranchos Formation present island-arc tholeiitic and calc-alkaline affinities. These variations mirror the geochemical evolution from proto- to first-arc lavas documented in subduction-initiation ophiolites. The extrusion of the Maimón Formation volcanic rocks is here contextualized in the forearc segment, close to the subducting proto- Caribbean spreading ridge, in a hot-subduction scenario. On the other hand, the extrusion of the Los Ranchos Formation volcanic rocks is contextualized in the forearc-apical arc segment, and their volcanic and volcanosedimentary deposits evidence the progression from submarine to subaerial conditions of deposition. Plagiotonalite batholiths, plagiorhyolite stocks and plagiorhyolites from the Maimón and Los Ranchos formations have tholeiitic and M-type affinities. Volcanogenic massive sulfide (VMS) mineralization hosted in the Maimón Formation and the lower basaltic unit of the Los Ranchos Formation took place during the subduction-initiation stage of the Caribbean island-arc. Subsequently, porphyry Cu-(Mo) - high sulfidation epithermal mineralization took over in the Los Ranchos Formation at ca. 112 Ma, likely connected to a spread episode of acid magmatism during the steady-state or true- subduction regime."--TDX.
