In this study, we make a quantitative assessment on the volatile flux of mantle-derived fluids and source of volatiles to explain the geologic controls on the transport of volatiles within thermal fluids of northeastern Anatolia. In line with this objective, we collected 22 samples (gas and water phase) from 16 geothermal fields in NE Turkey covering an area of nearly 100,000 km that extends from the eastern termination of North Anatolian Fault towards the Georgian and Armenian borders. The He/He ratios of the samples (R) normalized to the atmospheric He/He ratio (Ra = 1.4 × 10) vary from 0.31 to 7.15, and are considerably higher than the crustal value of 0.02Ra. Regarding spatial distribution of helium isotope composition, samples collected from areas of tectonic unrest around the Erzincan and Erzurum pull-apart basins in the southern part are represented by a higher range of He/He ratios (>5 Ra) than those in volcanic areas to the east and northeast of the region. δC values of the gas samples varying from −20.76 to 5.43 ‰ are about 4–5 ‰ lower than δC values of the water samples that range from −16.90 to 8.85 ‰, indicating CO removal from waters by degassing. CO/He ratios of gas samples falling in the range of 3.81 × 10 to 2.83 × 10 imply that carbon is derived from the mixing between the crustal lithologies and mantle, the latter having a contribution up to 40 %. The maximum flux of mantle-derived fluids is found 88 mm/a at Erzincan (eastern part of the North Anatolian Fault Zone). This value is higher by a factor of about 10 than the western part of the fault zone. Calculations show that degassing from magmatic bodies is the sole mechanism to explain the high helium isotope compositions in the region. Therefore, we suggest that mantle-derived He contents might be due to extensive melting associated with active tectonism. The He/Heat ratios of thermal waters in northeastern Turkey were calculated in range of 0.25 to 29.7 × 10 cm(STP)/J, consistent with the data reported for waters along the North Anatolian Fault, indicating a crustal heat source for the geothermal systems in northeastern Turkey.

中文翻译：

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安纳托利亚东北部热流体的氦和碳同位素组成：对热源和挥发通量的影响


在本研究中，我们对幔源流体的挥发通量和挥发物来源进行了定量评估，以解释安纳托利亚东北部热流体中挥发物运移的地质控制。为了实现这一目标，我们从土耳其东北部的 16 个地热田采集了 22 个样本（气相和水相），覆盖面积近 100,000 平方公里，从北安纳托利亚断层东端延伸至格鲁吉亚和亚美尼亚边境。样品的 He/He 比值 (R) 归一化为大气 He/He 比值 (Ra = 1.4 × 10)，范围为 0.31 至 7.15，远高于地壳值 0.02Ra。关于氦同位素组成的空间分布，从南部埃尔津詹和埃尔祖鲁姆拉分盆地周围的构造动荡地区采集的样品，其 He/He 比值 (>5 Ra) 范围高于火山地区的样品该地区的东部和东北部。气体样品的 δ13C 值在-20.76 到 5.43 ‰ 范围内，比水样的 δ13C 值在-16.90 到 8.85 ‰ 范围内低约 4–5 ‰，表明通过脱气从水中去除了 CO。气体样品的CO/He比值在3.81×10~2.83×10范围内，表明碳来源于地壳岩性和地幔的混合，后者的贡献高达40%。在埃尔津坎（北安纳托利亚断裂带东部）发现地幔衍生流体的最大通量为 88 毫米/年。该值比断裂带西部高出约10倍。计算表明，岩浆体脱气是解释该地区高氦同位素组成的唯一机制。 因此，我们认为，地幔来源的 He 含量可能是由于与活跃构造运动相关的广泛熔融所致。计算得出的土耳其东北部热水的氦/热比范围为 0.25 至 29.7 × 10 cm(STP)/J，与北安纳托利亚断层沿线水域报告的数据一致，表明地热系统的地壳热源在土耳其东北部。