Processes operating within magmatic crystal mushes exert a fundamental control on the physical and chemical evolution of mid-ocean ridge systems. It is widely recognized that mush fluidization in response to magma recharge could produce variable compositional zoning in crystals. However, olivines generally show relatively smooth MgFe zoning in comparison with complex and short-length scale zoning in plagioclases. It is still unclear about the proceedings of the olivine before the mush disaggregation immediately prior to eruption and unknown whether plagioclase zoning is genuinely more complex than olivine zoning. Here, using slow-diffusing elements X-ray maps, we identify complex compositional zoning in olivines from MORBs of the Southwest South China Sea (SCS) and thus provide mineralogical evidence for the re-organization within a mush that takes place over an extended period of time. Primitive olivines have homogeneous forsterite concentrations (Fo = 89.5 mol%), but preserve zoning in Al₂O₃ and Cr₂O₃. Multiple cores have anomalously low Al₂O₃ and Cr₂O₃ contents, with or without high P₂O₅, Al₂O₃, and Cr₂O₃ dendrites, and are surrounded by Al–Cr-rich but P-depleted mantles, in which boundaries between cores and mantles are sharply defined. This compositional and textural zoning indicates dissolution, re-equilibration, and re-growth of evolved olivine within primitive magmas, demonstrating a redistribution of crystals within a mush zone, consistent with mush fluidization. Therefore, primitive olivines, widely-used monitors of mantle processes, may also have undergone mush fluidization, such that apparently primitive olivines may result from the re-equilibration of evolved olivines with primitive melts. PAl zoning patterns in olivine can be used to evaluate the influence of mush processes on olivine mantle probes.

在岩浆晶状肌肉中进行的过程对中洋脊系统的物理和化学演化起了根本的控制作用。人们普遍认为，响应岩浆补给的糊状流化可以在晶体中产生可变的成分分区。但是，橄榄石通常显示出相对较光滑的Mg与斜长柄中的复杂和短尺度鳞片分区相比，Fe分区。尚不清楚火山喷发之前的糊状解体之前橄榄石的作用，并且尚不清楚斜长石分区是否真的比橄榄石分区更复杂。在这里，我们使用慢扩散元素X射线图，确定了西南南海（SCS）MORB橄榄石中的复杂成分区带，从而为长期处于糊状的重组提供了矿物学证据。时间。原始橄榄石具有均匀的镁橄榄石浓度（Fo = 89.5 mol％），但在Al ₂ O ₃和Cr ₂ O _3中保持分区。多芯异常低Al ₂O ₃和Cr ₂ O _3的含量，有或没有高P ₂ O ₅，Al ₂ O ₃和Cr ₂ O ₃树枝状晶，并被富含Al-Cr但贫P的地幔包围，其中岩心和地幔之间的边界清晰界定。这种成分和质地分区表明原始岩浆中演化的橄榄石溶解，重新平衡和重新生长，这表明结晶在浆糊区内重新分布，与浆糊流化相一致。因此，原始的橄榄石，地幔过程的广泛监测器，也可能经历了糊状流化作用，因此，显然原始的橄榄石可能是由于演化的橄榄石与原始熔体的重新平衡所致。橄榄石中的P Al分区模式可用于评估糊状过程对橄榄石地幔探针的影响。