Petrogenetic and metallogenetic responses to Miocene slab flattening: new constraints from the El Indio-Pascua Au–Ag–Cu belt, Chile/Argentina

Southern Central Andes Neogene magmatism over the Pampean Flat Slab: implications on crustal and slab melts contribution to magma generation in Precordillera, Western Argentina

“…First record of Neogene magmatism in a back arc position range between 22 to 20 Ma, represented by the Miocene Intrusives at the northern part of the Iglesia Valley. By the same time, main arc activity was represented by the latest stages of the Doña Ana Group magmatism, although pick of Neogene arc activity is represented by the lower section of the Cerro de las Tortolas Formation (~16-13 Ma) with mostly andesitic, medium-K calc-alkaline rocks (e.g., Maksaev et al, 1984;Bissig et al, 2003;Kay et al, 1991Kay et al, , 1999Litvak et al, 2007;Jones et al, 2016). Arc-related magmatism by this time was also developed towards the foreland, with the coetaneous intermediate subvolcanic and lavas f lows cropping out in Cerro Negro area, with ages around 15 Ma.…”

“…Later, during the Middle to Late Miocene (13-10 Ma), arc magmatic activity is represented by a more evolved dacitic calc-alkaline volcanism from the upper section of Cerro de las Tórtolas Formation and the dacitic to rhyolitic pyroclastic deposits from Tambo Formation (Bissig et al, 2003;Kay et al, 1991Kay et al, , 1999Litvak et al, 2007;Jones et al, 2016). Contemporaneously, arc-related magmatism was developed in an easternmost position, represented by the pyroclastic deposits and younger subvolcanic bodies cropping out in the eastern margin of the Cordillera del Colangüil, along the Iglesia Valley, ranging in age from 11 to 9 Ma (Fig.…”

“…Higher values of the Sm/Yb ratio are observed in the rocks of the Iglesia Valley when compared with their counterparts of the Frontal Cordillera (volcanic rocks of lower Cerro de las Tórtolas Formation and Vacas Heladas Ignimbrite), although the Iglesia Valley volcanic rocks show a normalized REE pattern with relatively minor LREE enrichment. The volcanic rocks of the main arc represented by the upper part of Cerro de las Tórtolas Formation contain the highest Sm/Yb ratios (Fig.8A) that show a passage to garnet as a residual mineral, which is interpreted as a gradual increase of the magma equilibrium depth within the crust (Kay et al, 1991(Kay et al, , 1999Bissig et al, 2003;Litvak et al, 2007).…”

“…This volcanic activity was coeval with the main volcanic arc developed at these latitudes, over the present-day Pampean f lat-slab region of Southern Central Andes. The geodynamic evolution of the Paleogene to Neogene main volcanic arc has been studied in the last years on the basis of chemical, petrographic and radiometric ages relationships of the involved volcanic units (Kay et al, 1991(Kay et al, , 1999Kay and Mpodozis, 2002;Bissig et al, 2001Bissig et al, , 2003Litvak et al, 2007;Litvak and Poma, 2005Jones et al, 2016); however, magmatic activity developed at the same latitudes but in a back arc position is less known. These deposits include a sedimentary and pyroclastic rock sequence known as Lomas del Campanario Formation (Wetten, 1975(Wetten, , 2005Contreras et al, 1990) and lava f lows related to shallow intrusives, named Miocene Intrusives and Tertiary Intrusives (Cardó and Díaz, 1999;Cardó et al, 2007;Llambías et al, 1990).…”

The genetic association of adakites and Cu–Au ore deposits

“…For example, some adakitic rocks do not have any deposits (Chiaradia et al 2004;Huang et al 2008), whereas some rocks without clear adakitic geochemical features are ore-bearing, for example some porphyry Cu and epithermal Au deposits in Ecuador (Chiaradia et al 2004) and small porphyry Cu deposits in the western Luzon (Imai 2002); in both cases calc-alkaline andesites are the host rocks. Therefore, it has been argued that high oxygen fugacity, rather than adakitic magma composition, is essential to the formation of porphyry Cu deposits (Imai 2002;Bissig et al 2003).…”