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  1. Understanding the processes that initiate volcanic eruptions after periods of quiescence are of paramount importance to interpreting volcano monitoring signals and mitigating volcanic hazards. However, studies of eruption initiation mechanisms are rarely systematically applied to high-risk volcanoes. Studies of erupted materials provide important insight into eruption initiation, as they provide direct insight into the physical and chemical changes that occur in magma reservoirs prior to eruptions, but are also often underutilized. Petrologic and geochemical studies can also constrain the timing of processes involved in eruption initiation, and the time that might be expected to elapse between remote detection of increased activity and eventual eruption. A compilation and analysis of literature data suggests that there are statistical differences in the composition, volume, style and timescales between eruptions initiated by different mechanisms. Knowledge of the processes that initiate eruptions at a given volcano may thus have significant predictive power. 
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    Free, publicly-accessible full text available July 18, 2024
  2. Free, publicly-accessible full text available May 1, 2024
  3. Abstract

    Extension within a continental back‐arc basin initiates within continental rather than oceanic lithosphere, and the geochemical characteristics of magmatic rocks within continental back‐arcs are poorly understood relative to their intraoceanic counterparts. Here, we compile published geochemical data from five exemplar modern continental back‐arc basins—the Okinawa Trough, Bransfield Strait, Tyrrhenian Sea, Patagonia plateau, and Aegean Sea/Western Anatolia—to establish a geochemical framework for continental back‐arc magmatism. This analysis shows that continental back‐arcs yield geochemical signatures more similar to arc magmatism than intraoceanic back‐arcs do. We apply this framework to published data for Triassic‐Jurassic magmatic rocks from the Caucasus arc system, which includes a relict continental back‐arc, the Caucasus Basin, that opened during the Jurassic and for which the causal mechanism of formation remains debated. Our analysis of40Ar/39Ar and U‐Pb ages indicates Permian‐Triassic arc magmatism from ∼260 to 220 Ma due to subduction beneath the Greater Caucasus and Scythian Platform. Late Triassic (∼220–210 Ma) collision of the Iranian block with Laurasia likely induced trench retreat in the Caucasus region and led to migration of the Caucasus arc and opening of the Caucasus Basin. This activity was followed by Jurassic arc magmatism in the Lesser Caucasus from ∼180 to 140 Ma and back‐arc spreading in the Caucasus Basin from ∼180 to 160 Ma. Trace element and Sr‐Nd isotopic data for magmatic rocks indicate that Caucasus Basin magmatism is comparable to modern continental back‐arcs and that the source to the Lesser Caucasus arc became more enriched at ∼160 Ma, likely from the cessation of back‐arc spreading.

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