Mapeamento geológico da Colina do Horto (Juazeiro do Norte, Ceará), com ênfase nas rochas ígneas

Abstract

The Horto Hill is an important landmark and geosite of the Cariri Cearense region. Through field mapping and petrographic/structural studies, it was possible to identify the lithostratigraphic units that make up its foundation and to raise hypotheses about its geological evolution, especially during the Neoproterozoic. In this work, the Logradouro and Santo Sepulcro Plutons are defined as two diachronic stocks which intrude low-grade metasedimentary and metavolcanic rocks belonging to the Santana dos Garrotes Formation, deformed during a dextral transpressive event coeval to the first Pluton, but earlier than the second one. Through petrographical analysis, it was possible to classify the Logradouro Pluton as being formed by tonalites, granodiorites, monzogranites and diorites with magmatic epidote, associated with muscovite trondhjemites, similar to the region’s Conceição Suite; while the Santo Sepulcro one is composed of monzogranites and sienogranites porphyritic to equigranular associated with aplitic to pegmatitic leucogranites, which bear resemblance to the Itaporanga Suite. The granites and metamorphites are covered by a Cambro-Ordovician paleosol, which in turn is overlain by siliciclastic sedimentary rocks from the Cariri and Brejo Santo Formations of the Araripe Basin. Ancient colluvial-alluvial deposits and recent alluvium make up the rest of the lithological framework in the area. Based on the overall morphology of the Hill, as well as a comparison with other landforms in the Cariri Valley, its epirogenesis is interpreted as a result of neotectonic reactivation of the Araripe Basin’s edge faults, generating a series of en echelon structural highs in the region.