Characteristics, distribution and implication of hydrothermal minerals in Tianxiu Hydrothermal Field, Carlsberg Ridge, northwest Indian Ocean
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摘要:
海底沉积物中的热液成因矿物主要来自热液区热液产物堆积体的失稳垮塌搬运迁移和热液羽流自生矿物颗粒的沉降。热液成因矿物的类型和空间分布特征对于了解热液活动区的位置与范围具有重要的指示作用。天休热液区(3°41′N、63°50′E)位于卡尔斯伯格脊超镁铁岩系中,本文对采自该热液区及其周边的共4站表层沉积物样品进行研究,分析热液成因矿物的组成、丰度和粒度的空间变化情况。研究表明,在热液喷口近端(0 ~0.22 km)同时分布有垮塌迁移及热液羽流沉降来源的热液成因矿物,其中垮塌来源的矿物呈砾—粗砂级,以古巴矿等金属硫化物矿物及铁氧化物为主;羽流沉降来源的矿物呈砂—泥级,以Cu-Zn-Fe硫化物矿物(等轴古巴矿、古巴矿、闪锌矿和磁黄铁矿等)为主。在远喷口端(1.84 ~ 6.05 km)主要分布有羽流沉降来源的热液成因矿物,以砂—泥级的金属氧化物和氢氧化物为主。热液成因矿物的类型、粒度、丰度在空间上呈现出的规律性分布特征可以示踪未知的活动和非活动热液区的位置,并作为多金属硫化物资源的找矿标志。
Abstract:Hydrothermal minerals could originate from mass wasting of hydrothermal deposits or from the hydrothermal plume falling-out. The types and their spatial distribution of hydrothermal minerals are important indicators for constraining the location of hydrothermal field. The Tianxiu Hydrothermal Field (3°41′N,63°50′E) is an ultramafic-hosted field located on the Carlsberg Ridge, northwest Indian Ocean. In this paper, surface sediments collected from 4 stations near the active venting site of Tianxiu Hydrothermal Field and its surrounding regions were studied on hydrothermal minerals to understand their spatial variations on morphology, composition, abundance and particle size. Near the venting site (0 ~ 0.22 km) the hydrothermal minerals are dominated by Cu-Zn-Fe containing sulfide aggregates, in the size from gravel to sand, originated from the mass wasting of the sulfide deposits and precipitation from the hydrothermal fluid. For samples collected outside of the hydrothermal field (1.84 ~ 6.05 km away), the hydrothermal minerals are dominated by fine grain hydrothermal oxides and hydroxides derived from plume fallout. Our results suggest that the types and grain size of hydrothermal minerals and their spatial distribution can be served as a good indicator for tracking unknown active and inactive hydrothermal field and prospecting of the associated hydrothermal sulfide resources.
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Key words:
- surface sediments /
- hydrothermal minerals /
- Tianxiu Hydrothermal Field /
- Carlsberg Ridge /
- Indian Ocean
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表 1 采样位置信息
Table 1. The coordinates of sampling stations
站位号 纬度(N) 经度(E) 水深/m 采样位置 33I-TVG07 3.68 63.83° 3 504 活动热液喷口处 26I-TVG05 3.69° 63.83° 3 477 活动热液喷口西南侧0.22 km 26I-TVG04 3.70° 63.82° 3 611 活动热液喷口西北侧1.84 km 33I-TVG11 3.66° 63.79° 2 789 活动热液喷口西南侧6.05 km 表 2 粒径<1 mm沉积物中主要矿物半定量统计分析
Table 2. Abundance of major minerals in sediments with grain size <1 mm
矿物名称 理想化学式 近端 远端 33I-TVG07 26I-TVG05 26I-TVG04 33I-TVG11 金属硫化物 磁黄铁矿 Fe1-XS ++ + 黄铁矿 FeS2 ++ ++ 闪锌矿 (Zn,Fe)S ++ + 古巴矿/等轴古巴矿 CuFe2S3 ++ + 金属氧化物 铁的氧化物/氢氧化物 Fe2O3/Fe3O4/Fe-(Mn)-OOH ++ ++ + + 围岩碎屑 +++ +++ 钙质生物碎屑 + + +++ +++ 注:+++ 代表数量百分比>70%,++ 代表数量百分比1%~10%,+ 代表数量百分比<1%。 -
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