## 1 Introduction
### Geochemistry of CAVA and Aims of This Study
The sampling sites abbreviation is explicated in Table 1.  
\begin{table}
\begin{tabular}{l l l c c c c c c c c c c c c c c} \hline \hline
**Sample** & \multicolumn{2}{c}{**Period of**} & \multicolumn{2}{c}{**\({}^{\textbf{3}}\)He**} & \multicolumn{2}{c}{**\({}^{\textbf{4}}\)He**} & \multicolumn{2}{c}{**\({}^{\textbf{20}}\)Ne**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{36}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{4}}\)He\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)He/\({}^{\textbf{40}}\)Ne**} & \multicolumn{2}{c}{**R/Ra**} & \multicolumn{2}{c}{**Err. **} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar/\({}^{\textbf{60}}\)Ar**} & \multicolumn{2}{c}{**Err. **} \\
**ID** & \multicolumn{2}{c}{**Volcanism**} & \multicolumn{2}{c}{**Minreal**} & \multicolumn{2}{c}{**\({}^{\textbf{3}}\)He**} & \multicolumn{2}{c}{**\({}^{\textbf{3}}\)He**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ne**} & \multicolumn{2}{c}{**\({}^{\textbf{36}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar**} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)He/\({}^{\textbf{40}}\)Ne**} & \multicolumn{2}{c}{**R/Ra**} & \multicolumn{2}{c}{**Err. **} & \multicolumn{2}{c}{**\({}^{\textbf{40}}\)Ar/\({}^{\textbf{60}}\)Ar**} & \multicolumn{2}{c}{**Err. **} \\  & & & & & & & & & & & &  
In order to help in filling this gap of knowledge, we present in this work the first \({}^{3}\)He/\({}^{4}\)He results for FI in Ol and Px separated from rocks of two poorly studied volcanic systems of CAVA: Telica, in Nicaragua, and Baru, in Panama. The study of FI in Ol and Px, together with their mineralogical and petrological features, provides the opportunity to look directly at the magmatic fluids degassed in the plumbing system, thus providing complementary information with respect to fumarole and hydrothermal gases. Telica is among the most active open-vent degassing volcanoes of basaltic andesite composition in the Central American Volcanic Arc (CAVA) [31; 64]. Its seismic activity and major gas emissions have been closely examined over recent years [65]. Volcanic activity includes violent strombolian explosions and minor vulcanian events, interspersed with frequent minor phreatomagmatic events [65]. Baru is the most recent stratovolcano in Panama with documented historic activity (1550 \(\pm\) 10 years; [66; 67; 68]). The summit of the volcano rises at 3374 m above sea level, the whole morphology constitutes a massive composite stratovolcano of between 400-450 km\({}^{3}\)[15; 66; 67; 68]. Volcanic rock activity in the Baru region has been recorded since the early Tertiary [67; 68] period, and the main volcano building stages in the Pleistocene-to-Holocene [12] include large explosive eruptions. These two volcanoes, apart from being poorly studied in terms of \({}^{3}\)He/\({}^{4}\)He of magmatic gases, are located in contrasting segments of the CAVA, as Telica magmatism is strongly influenced by subducting sediment fluids, while Baru is located in the Quaternary arc segment of Panama, considered still active but originating from the oblique subduction of the Nazca plate that includes the Galapagos seamount. We constrained the \({}^{3}\)He/\({}^{4}\)He signature of these magmatic systems and put our results in the context of previous results obtained from other CAVA volcanic systems. This information is finally integrated with previous knowledge on rock geochemistry along CAVA. This allows us to evaluate the possible modifications of the pristine \({}^{3}\)He/\({}^{4}\)He of the mantle portions beneath the studied volcanoes (e.g., [69; 70; 71]), in response to subduction parameters and crustal thickness.