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首页> 外文期刊>Contributions to Mineralogy and Petrology >Geochemical investigation of a semi-continuous extrusive basaltic section from the Deccan Volcanic Province, India: implications for the mantle and magma chamber processes
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Geochemical investigation of a semi-continuous extrusive basaltic section from the Deccan Volcanic Province, India: implications for the mantle and magma chamber processes

机译：印度德干火山省半连续挤压玄武岩剖面的地球化学研究：对地幔和岩浆腔过程的影响

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Spatial and temporal variations in the geochemistry of an extrusive basaltic section of Deccan traps record progressive changes in mantle melting and crustal filtration and are relevant to understand continental flood basalt (CFB) magmatism. In the present work we have carried out detailed field, petrographic, density and magnetic susceptibility, and geochemical investigations on a small, semi-continuous extrusive section in the eastern Deccan Volcanic Province (DVP) to understand the role of shallow magma chambers in CFB magmatism. Four formations, Ajanta, Chikhli, Buldhana and Karanja crop out in the Gangakhed–Ambajogai area with increasing elevation. Our studies indicate that: (1) the Karanja Formation represents a major magma addition, as indicated by abrupt change in texture, increases in MgO, CaO, Ni, Cr, and Sr, and drastic decreases in Al2O3, Na2O, K2O, Rb, Ba, REE, bulk-rock density and magnetic susceptibility; (2) assimilation fractional crystallization, crystal-laden magmas, and accessory cumulus phases influence the trace element chemistry of Deccan basalts; (3) the predicted cumulate sequence of olivine gabbro–leucogabbro–oxide-apatite gabbro is supported by the observed layered series in a shallow magma chamber within the DVP; (4) the initial magma was saturated with olivine, plagioclase, and augite, and final the pressure of equilibration for the Gangakhed–Ambajogai section basalts is ~2 kbar (~6 km depth); (5) petrophysical parameters act as proxies for magmatic processes; (6) a small layer of oxide-rich basalts may represent the latest erupted pulse in a given magmatic cycle in the DVP; (7) parental basalts to some of the red boles, considered as formation boundaries, might represent small degree partial melts of the mantle; (8) SW Deccan basaltic-types continue into the eastern DVP; and (9) in addition to the magma chamber processes, dynamic melting of the mantle may have controlled DVP geochemistry. The present study underscores the importance of mapping specific stratigraphic intervals in limited areas to understand mantle and magma chamber processes relevant to CFB magmatism.
机译：Deccan圈套的挤压玄武岩剖面地球化学的时空变化记录了地幔融化和地壳过滤的逐步变化，与了解大陆洪水玄武岩（CFB）岩浆作用有关。在目前的工作中，我们对东部德干火山省（DVP）的一个小的半连续挤压剖面进行了详细的野外，岩相，密度和磁化率以及地球化学研究，以了解浅层岩浆室在CFB岩浆作用中的作用。 。随着海拔的升高，Gangakhed–Ambajogai地区出现了Ajanta，Chikhli，Buldhana和Karanja这四个编队。我们的研究表明：（1）Karanja组是主要的岩浆添加，如质地的突然变化，MgO，CaO，Ni，Cr和Sr的增加以及Al 2 O 3 ，Na 2 O，K 2 O，Rb，Ba，REE，块岩密度和磁化率； （2）同化分数结晶，含晶岩浆和副积云相影响Deccan玄武岩的微量元素化学性质； （3）DVP内部浅层岩浆室内的层状层序支持了橄榄石辉长岩-白云岩-氧化物-磷灰石辉长岩的预计累积序列； （4）最初的岩浆充满了橄榄石，斜长石和辉长岩，最后，Gangakhed-Ambajogai断面玄武岩的平衡压力为〜2 kbar（〜6 km深）； （5）岩石物理参数是岩浆作用的代理； （6）一小层富含氧化物的玄武岩可能代表了DVP中给定岩浆循环中最新爆发的脉冲； （7）一些红场的亲子玄武岩，被认为是地层边界，可能代表着地幔的小程度部分融化； （8）西南部Deccan玄武岩类型继续进入东部DVP； （9）除了岩浆室过程外，地幔的动态融化还可能控制了DVP地球化学。本研究强调了在有限区域内绘制特定地层间隔以了解与CFB岩浆作用有关的地幔和岩浆室​​过程的重要性。

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