Mantle-derived helium in hot springs of the Cordillera Blanca, Peru: Implications for mantle-to-crust fluid transfer in a flat-slab subduction setting
Mantle-derived helium in hot springs of the Cordillera Blanca, Peru: Implications for mantle-to-crust fluid transfer in a flat-slab subduction setting
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秘鲁布兰卡山脉温泉中源自地幔的氦气：对平板俯冲环境中地幔到地壳流体转移的影响
DOI：
10.1016/j.chemgeo.2015.10.003
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发表时间：
2015
期刊：
影响因子：
3.9
通讯作者：
Hughes, Cameron A.
中科院分区：
文献类型：
--
作者：
Newell, Dennis L.;Jessup, Micah J.;Hilton, David R.;Shaw, Colin A.;Hughes, Cameron A.
秘鲁科迪勒拉布兰卡断层控制的温泉提供了现代板块俯冲背景下幔源流体的地球化学证据。安第斯山脉是秘鲁安第斯山脉的最高峰，位于安第斯弧的一个岩浆区。科迪勒拉布兰卡拆离确定了范围的西南边缘，并记录了自5 Ma以来自上而下向西的韧性剪切到脆性正断层的进展。温泉，记录温度高达78 °C，沿着沿着这个断层带流出，是富含CO2、接近中性、碱性氯化物到碱性碳酸盐沃茨，具有高微量金属含量，包括砷（≤ 11 ppm）。水δ 18 OSMOW（− 14.2至− 4.9‰）和δDSMOW（− 106.2至− 74.3‰）、元素化学趋势和阳离子地质温度测量共同表明热（200-260 °C）盐水与冷大气水沿着断层混合。沃茨中溶解气体的氦同位素比值（3 He/4 He）在0.62 ~ 1.98 RA之间（RA=空气3 He/4 He），表明存在高达25%的幔源氦。鉴于长期以来，和大的距离，在该地区的活跃岩浆活动，并可能存在撕裂的平坦板南部的科迪勒拉布兰卡，我们认为，地幔氦可能来自软流圈进入板撕裂，或从大陆地幔岩石圈，动员来自板脱水的交代流体。
Fault-controlled hot springs in the Cordillera Blanca, Peru provide geochemical evidence of mantle-derived fluids in a modern flat-slab subduction setting. The Cordillera Blanca is an ~ 200 km-long mountain range that contains the highest peaks in the Peruvian Andes, located in an amagmatic reach of the Andean arc. The Cordillera Blanca detachment defines the southwestern edge of the range and records a progression of top-down-to-the-west ductile shear to brittle normal faulting since ~ 5 Ma. Hot springs, recording temperatures up to 78 °C, issue along this fault zone and are CO2-rich, near neutral, alkaline-chloride to alkaline-carbonate waters, with elevated trace metal contents including arsenic (≤ 11 ppm). Water δ18OSMOW(− 14.2 to − 4.9‰) and δDSMOW(− 106.2 to − 74.3‰), trends in elemental chemistry, and cation geothermometry collectively demonstrate mixing of hot (200–260 °C) saline fluid with cold meteoric water along the fault. Helium isotope ratios (3He/4He) for dissolved gases in the waters range from 0.62 to 1.98 RA(where RA= air3He/4He), indicating the presence of up to 25% mantle-derived helium. Given the long duration since, and large distance to active magmatism in the region, and the possible presence of a tear in the flat slab south of the Cordillera Blanca, we suggest that mantle helium may originate from asthenosphere entering the slab tear, or from the continental mantle-lithosphere, mobilized by metasomatic fluids derived from slab dehydration.
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影响因子：
56.9
作者：
Kennedy, BM;Kharaka, YK;Mariner, RH
通讯作者：
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影响因子：
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作者：
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