Petrology,geochemistry,and crystal size distribution of the basaltic andesite-dacite association at Mt.Sumbing,Central Java,Indonesia:Insights to magma reservoir dynamics and petrogenesis  

作　　者：Indranova Suhendro Endra Yuliawan Revina Fitri Zen Zulfa Yogi Rahmawati Pandu Eka Priyana Sonna Diwijaya Muhammad Alsamtu Tita Sabila Pratama Suhartono Andre Jonathan Gammanda Adhny El Zamzamy Latief 

机构地区：[1]Department of Environmental Geography,Faculty of Geography,Universitas Gadjah Mada,Sekip Utara Jl.Kaliurang,Bulaksumur,Yogyakarta 55281,Indonesia [2]Centre for Disaster Studies,Universitas Gadjah Mada,Jl.Mahoni C-16,Bulaksumur,Yogyakarta 55281,Indonesia

出　　处：《Acta Geochimica》2024年第5期838-855,共18页地球化学学报（英文）

基　　金：funded by the Faculty of Geography under the scheme of“Dana Hibah Penelitian Mandiri Dosen Tahun 2023 Tahap 1”。

摘　　要：Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The stratigraphy is arranged as LF1,PDC1,LF2,LF3,LF4,LF5,LF6,LF7,LD1,and LD2;furthermore,these rocks were divided into two types.TypeⅠ,observed in the oldest(LF1)sample,has poor MgO and high Ba/Nb,Th/Yb and Sr.The remaining samples(PDC1–LD2)represent typeⅡ,characterized by high MgO and low Ba/Nb,Th/Yb and Sr values.We suggest that type I is derived from AOC(altered oceanic crust)-rich melts that underwent significant crustal assimilation,while typeⅡoriginates from mantle-rich melts with less significant crustal assimilation.The early stage of typeⅡmagma(PDC1–LF3)was considered a closed system,evolving basaltic andesite into andesite(55.0–60.2 wt%SiO_(2))with a progressively increasing phenocryst(0.30–0.48φ_(PC))and decreasing crystal size distribution(CSD)slope(from-3.9 to-2.9).The evidence of fluctuating silica and phenocryst contents(between 55.9–59.7 wt%and 0.25–0.41φ_(PC),respectively),coupled with the kinked and steep(from-5.0 to-3.3)CSD curves imply the interchanging condition between open(i.e.,magma mixing)and closed magmatic systems during the middle stage(LF4–LF6).Finally,it underwent to closed system again during the final stage(LF7–LD2)because the magma reached dacitic composition(at most 68.9 wt%SiO_(2))with abundant phenocryst(0.38–0.45φ_(PC))and gentle CSD slope(from-4.1 to-1.2).

关 键 词：Sumbing Whole-rock geochemistry PETROGENESIS FRACTIONATION Magma mixing Crystal size distribution 

分 类 号：P588.1[天文地球—岩石学]