biotite, hornblende, iron oxide, plagioclase, pyroxene and titanium oxide; degraded olivine is also found. The magmas formed at temperatures of with uncertainties of ; the highest temperatures are associated with the 1992 eruption products. Isotope data indicate that the pre-magmas interacted with the crust at great depths before rising to shallower magma chambers. In these shallower magma chambers, magma genesis involved processes of magma mixing which formed at least part of the andesites and fractional crystallization which gave rise to the dacites. Partial crystallization and flow events within the magma chamber caused the formation of the andesite enclaves. The total magma production rate of Sabancaya without accounting for repose periods is about . Sabancaya is a source of volcanic gases such as and . The amount of water emitted by Sabancaya is noticeably large for a volcano (about ); the source of this water might be an evaporating hydrothermal system in the volcano. Together with Ubinas Sabancaya is among the main emitters of and in the Central Volcanic Zone of the Andes and among the top fifteen volcanic emitters on Earth. Eruptive history Initially, Ampato volcano was the active volcano before volcanism shifted to Sabancaya, after a period where both volcanoes erupted. Presently, most activity at Sabancaya occurs in the form of lava domes and lava flows, one of which is dated to 5,440 ±40 years before present on the eastern flank. Additional surface exposure dating has yielded ages of 6,650 ±320 and 6,300 ±310 on various lava flows, indicating that effusive activity started shortly after the beginning of the Holocene although the basal part of the edifice did not exist yet at that time. Pyroclastic eruptions are less common and have a low volume, with one such occurrence dated to 8,500 years before present. This tephra layer, along with layers dated 2500-2100 BC, 420–150 BC, 100 BC – 150 AD and between 1200 and 1400 AD, could have originated either on Sabancaya or Ampato, however. There is evidence that early and middle-Holocene Sabancaya mostly erupted lava, while the late-Holocene volcano was more explosive in its activity. It is possible that the Inca performed human sacrifices in response to eruptions of Sabancaya to calm down the mountain spirits. Spanish chronicles mention probable eruptions in 1752 and 1784, which might have left layers of tephra. After the 18th century, the volcano went dormant for about two hundred years during which only