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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Constraints on origin and evolution of Red Sea brines from helium and argon isotopes
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Constraints on origin and evolution of Red Sea brines from helium and argon isotopes

机译：氦和氩同位素对红海盐水的起源和演化的限制

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摘要

Brines from three depressions along the axis of the Red Sea, the Atlantis II, the Discovery and the Kebrit Deep, were sampled and analyzed for helium and argon isotopes. We identified two principally different geochemical fingerprints that reflect the geological setting of the deeps. The Atlantis II and the Discovery brines originating from locations in the central Red Sea show ~4He concentrations up to 1.2 * 10~(-5) cm~3 STP g~(-1) and a ~3He/~4He ratio of 1.27 * 10~(-5). The MORB-like ~3He/~4He ratio is typical of an active hydrothermal vent system and clearly indicates a mantle origin of the helium component within the brines. ~(40)Ar/~(36)Ar ratios are as high as 305 implying that mantle-derived ~(40)Ar excesses of up to 3% of the total argon concentration are present in the brines and transported along with the mantle helium signal. The mean (~4He/~(40)Ar)_(excess) ratio of 2.1 is in agreement with the theoretical mantle production ratio. In the Kebrit Deep, located in the northern Red Sea, we found a helium excess of 5.7 * 10~(-7) cm~3 STP g~(-1). The low ~3He/~4He ratio of 1 * 10~(-6) points to a predominantly radiogenic source of the helium excess with only a minor mantle contribution of approximately 9%. We propose a new scenario assuming that the Kebrit brine accumulates a diffusive helium flux that migrates from deeper sedimentary or crustal horizons. In contrast to the Atlantis II and Discovery Deep, the Kebrit brine shows no sign of an active hydrothermal input.
机译：对沿红海，亚特兰提斯二号，发现号和凯布里特深海沿线三个凹陷的盐水进行采样并分析了氦和氩同位素。我们确定了两个主要不同的地球化学指纹，它们反映了深层的地质环境。来自红海中部地区的Atlantis II和Discovery盐水显示〜4He浓度高达1.2 * 10〜（-5）cm〜3 STP g〜（-1），〜3He /〜4He比为1.27 * 10〜（-5）。类似于MORB的〜3He /〜4He比是主动热液排放系统的典型特征，它清楚地表明了盐水中氦成分的地幔起源。 〜（40）Ar /〜（36）Ar之比高达305，这意味着盐水中存在源自地幔的〜（40）Ar过量，占总氩气浓度的3％，并与地幔氦一起运输信号。 2.1的平均（〜4He /〜（40）Ar）_（过量）比率与理论地幔生产比率一致。在红海北部的凯布里特深处，我们发现氦气过量为5.7 * 10〜（-7）cm〜3 STP g〜（-1）。 1 * 10〜（-6）的〜3He /〜4He低比率表明氦是过量的主要放射源，仅有约9％的较小地幔贡献。我们提出了一个新的假设，假设Kebrit盐水积累了从较深的沉积层或地壳层迁移的扩散氦气通量。与Atlantis II和Discovery Deep相比，Kebrit盐水没有显示出活跃的热液输入迹象。

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