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| 1 | 沉积物再循环引起的地幔氧化及其对地幔富铁熔体成因的启示显示文摘地幔起源熔体FeO^tot含量通常在11 wt%左右,但也有些原始熔体异常富铁(FeO^tot>13 wt%).因此富铁熔体是研究地幔不均一性的理想样品,而且一些大型氧化物及硫化物矿床也和其密切相关.然而到目前为止富铁熔体的成因仍没有定论.在内蒙古达里湖武岩中发现了一类比较特殊的地幔橄榄岩包体,其中包含有极高Mg#橄榄石和高Fe^3+/ΣFe比值矿物(镁铁矿及赤铁矿).这些矿物组合记录了地幔强氧化环境.因为这些橄榄岩包体和碳酸岩质包体一同出现,而且其中的单斜辉石具有明显的Sr同位素环带变化,所以强氧化条件可能是由再循环沉积物诱发的.本文模拟了地幔橄榄岩及辉石岩在不同氧逸度条件下的熔融行为,发现高氧逸度条件下形成的熔体具有富铁苦橄岩的典型特征(高FeO和MgO、低Al2O3).这些观察表明氧化地幔熔融可能是富铁熔体的另一种形成机制. | 何德涛 刘勇胜 陈春飞 Stephen F.Foley Mihai N.Ducea | 2020 | Science Bulletin2020，65，7： | 6 |
| 2 | 再循环碳酸岩火山作用对新元古代碳酸盐碳同位素显著负偏的贡献显示文摘埃迪卡拉纪晚期Shuram碳酸盐记录了地球历史上最显著的碳同位素负偏(δ^(13)C=-12‰)现象(简称SE).前人认为SE事件是溶解有机质氧化、成岩作用或者自生沉淀作用的结果.上述机制面临着巨量的大气氧以及大量δ^(13)C极负物质的持续输入等多方面挑战.本文研究表明记录SE的典型地层华南九龙湾剖面中的陡山陀组具有与高温过程相关的矿物学和地球化学特征.碳同位素负偏样品中铁白云石、长石、碳硅石和自形石英的出现以及碳酸盐Ce异常和石英O同位素组成稳定的特征均表明有高温火成作用的参与.此外,碳同位素负偏样品的微量元素和碳同位素组成与沉积碳酸盐岩通过脱碳熔融作用形成的再循环碳酸岩一致.这些特征表明与罗迪尼亚超大陆裂解有关的古老碳酸盐岩在俯冲过程中经过脱碳作用后形成的碳酸岩岩浆喷发可能是引起SE的原因.这种火成模型可能提供了地球深部和浅部碳循环之间的联系. | 刘勇胜 陈唯 Stephen F.Foley 沈延安 陈春飞 李俊华 欧晓斌 何德涛 冯庆来 蔺洁 | 2021 | Science Bulletin2021，66，18： | 3 |
| 3 | 火山磷供给推动中国北方中生代陆地生物繁荣显示文摘中国北方中生代热河生物群的生物量和生物多样性超过了同时期的其他陆地生物群,早白垩世热河生物群的辐射可能是对华北克拉通峰期破坏过程的响应,然而,克拉通破坏的深部过程和陆地生物群演化之间的内在联系尚不清楚。磷是生命所必需的营养元素,火山产物(包括熔岩和火山碎屑岩)中的磷可通过风化作用供给陆地生态系统。中国北方中生代连续的火山-沉积序列记录了火山磷供给、生物生产力和物种丰度的变化,为研究地球深部过程、火山作用与陆地生物群的协同演化提供了关键证据.火山磷供给与生物群演化之间的耦合关系表明,在华北克拉通峰期破坏期间,大量火山产物的风化作用为陆地生态系统供给了丰富的营养物质,创造了有利于热河生物群繁荣的陆地环境。与华北克拉通破坏初期相对应的侏罗纪燕辽生物群的演化也反映了上述火山-生物之间的耦合机制。 | 马超 汤艳杰 Ross N.Mitchell 李永飞 孙守亮 朱吉昌 Stephen F.Foley 王敏 叶辰阳 英基丰 朱日祥 | 2023 | Science Bulletin2023，68，12： | 1 |
| 4 | Melting of hydrous pyroxenites with alkali amphiboles in the continental mantle:1.Melting relations and major element compositions of melts显示文摘Melting experiments on ultramafic rocks rich in the hydrous minerals phlogopite or phlogopite+K-rich terite,some including 5%of accessory phases,have been conducted at 15 and 50 kbar.The assemblages represent probable source components that contribute to melts in cratonic regions,but whose melt compositions are poorly known.A main series of starting compositions based on MARID xenoliths consisted of a third each of clinopyroxene(CPX),phlogopite(PHL)and K-richterite(KR)with or without 5%ilmenite,rutile or apatite.Additional experiments were run without KR and with higher proportions of accessory phases.Melt traps were used at near-solidus temperatures to facilitate accurate analysis of wellquenched melts,for which reversal experiments demonstrate equilibrium.Results show that KR melts rapidly and completely within 50°C of the solidus,so that melts reflect the composition of the amphibole and its melting reaction.Melts have high SiO_(2) and especially K_(2)O but low CaO and Al_(2)O_(3) relative to basaltic melts produced from peridotites at similar pressures.They have no counterparts amongst natural rocks,but most closely resemble leucite lamproites at 15 kbar.KR and PHL melt incongruently to form olivine(OL)and CPX at 15 kbar,promoting SiO2 contents of the melt,whereas orthopyroxene OPX is increasingly stable at lower lithosphere pressures,leading to an increase in Mg O and decrease in SiO_(2) in melts,which resemble olivine lamproites.Melts of mica pyroxenites without KR are richer in CaO and Al_(2)O_(3) and do not resemble lamproites.These experiments show that low CaO and Al_(2)O_(3) in igneous rocks is not necessarily a sign of a depleted peridotite source.Accessory phases produce melts exceptionally rich in P_(2)O_(5) or TiO_(2) depending on the phases present and are unlike any melts seen at the Earth’s surface,but may be important agents of metasomatism seen in xenoliths.The addition of the 5%accessory phases ilmenite,rutile or apatite result in melting temperatures a few ten of degrees lower;at least two of these appear essential to explain the compositions of many alkaline igneous rocks on cratons.Melting temperatures for CPX+PHL+KR mixtures are close to cratonic geotherms at depths>130 km:minor perturbations of the stable geotherm at>150 km will rapidly lead to 20%melting.Melts of hydrous pyroxenites with a variety of accessory phases will be common initial melts at depth,but will change if reaction with wall-rocks occurs,leading to volcanism that contains chemical components of peridotite even though the temperature in the source region remains well below the melting point of peridotite.At higher temperatures,extensive melting of peridotite will dilute the initial alkaline melts:this is recognizable as alkaline components in basalts and,in extreme cases,alkali picrites.Hydrous pyroxenites are,therefore,components of most mantle-derived igneous rocks:basaltic rocks should not be oversimplified as being purely melts of peridotite or of mixtures of peridotite and dry pyroxenite without hydrous phases. | Stephen F.Foley Isra S.Ezad Sieger R.van der Laan Maik Pertermann | 2022 | Geoscience Frontiers2022，13，4： | 1 |
| 5 | Melting of hydrous pyroxenites with alkali amphiboles in the continental mantle:2.Trace element compositions of melts and minerals显示文摘The trace element compositions of melts and minerals from high-pressure experiments on hydrous pyroxenites containing K-richterite are presented. The experiments used mixtures of a third each of the natural minerals clinopyroxene, phlogopite and K-richterite, some with the addition of 5% of an accessory phase ilmenite, rutile or apatite. Although the major element compositions of melts resemble natural lamproites, the trace element contents of most trace elements from the three-mineral mixture are much lower than in lamproites. Apatite is required in the source to provide high abundances of the rare earth elements, and either rutile and/or ilmenite is required to provide the high field strength elements Ti, Nb, Ta, Zr and Hf. Phlogopite controls the high levels of Rb, Cs and Ba.Since abundances of trace elements in the various starting mixtures vary strongly because of the use of natural minerals, we calculated mineral/melt partition coefficients (DMin/melt) using mineral modes and melting reactions and present trace element patterns for different degrees of partial melting of hydrous pyroxenites. Rb, Cs and Ba are compatible in phlogopite and the partition coefficient ratio phlogopite/K-richterite is high for Ba (136) and Rb (12). All melts have low contents of most of the first row transition elements, particularly Ni and Cu ((0.1-0.01)×primitive mantle). Nickel has high DMin/melt for all the major minerals (12 for K-richterite, 9.2 for phlogopite and 5.6 for Cpx) and so behaves at least as compatibly as in melting of peridotites. Fluorine/chlorine ratios in melts are high and DMin/melt for fluorine decreases in the order apatite (2.2) > phlogopite (1.5) > K-richterite (0.87). The requirement for apatite and at least one Ti-oxide in the source of natural lamproites holds for mica pyroxenites that lack K-richterite. The results are used to model isotopic ageing in hydrous pyroxenite source rocks: phlogopite controls Sr isotopes, so that lamproites with relatively low 87Sr/86Sr must come from phlogopite-poor source rocks, probably dominated by Cpx and K-richterite. At high pressures (>4 GPa), peritectic Cpx holds back Na, explaining the high K2O/Na2O of lamproites. | Stephen F.Foley Isra S.Ezad | 2024 | Geoscience Frontiers2024，15，1： | 0 |
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