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CDE热液场是中国在劳盆地东部扩张中心区域发现的热液场.本文报道了该热液场小型低温富Si烟囱体的矿物学、地球化学分析结果.矿物学分析发现,烟囱体壁的矿物具有着明显的环带结构:沿烟囱主通道内壁向外,分别由蛋白石+重晶石层,长杆状蛋白石层,Fe-Si质丝缕体层以及最外面的Fe-Mn氧/羟化物(以下简称Fe-Mn氧化物)层组成.蛋白石的氧同位素测温表明最内层蛋白石和重晶石层的沉淀温度为68.5℃,而次内层长杆状蛋白石层为39.6℃,具有明显的温度梯度.同时,稀土元素的各个指标(Eu/Eu*,Ce/Ce*与(La/Yb)N)以及从不同层位烟囱体壁提取到的Fe-Mn氧化物的Sr同位素比值均在次外层有明显异常,暗示该烟囱体在发育的初始阶段,最先形成的外壁是当前的次外层.形态学观察表明嗜中性Fe氧化菌的微生物和某些可能利用Si的微生物在烟囱体的构建过程中起到了重要作用,其代谢活动形成的Fe-Si质丝缕体和少量蛋白石以及重晶石沉淀最先形成环状的原始外壁,并与后期出现的长杆状蛋白石一起交织成三维立体网络,通过逐步矿化增生影响了烟囱体壁的渗透能力,最终控制了海水和热液的混合比例,导致低温富Si烟囱体的环带状结构的形成.元素地球化学分析还表明,矿物的环带特征以及Fe-Mn氧化物的对周围水体中元素的“吸附作用”控制了烟囱体的地球化学特征.
The CDE hydrothermal field is a hydrothermal field discovered in the central expansion basin of the eastern basin of Laohuo basin.This paper reports the mineralogical and geochemical analysis results of the small-scale, low-temperature, Si-rich chimney body in this hydrothermal field.The mineralogical analysis shows that the chimney wall The minerals have obvious ring structure: along the inner wall of the main channel of the chimney, they are composed of opal + barite layer, long rod-shaped opal layer, Fe-Si layer and outermost Fe-Mn oxygen / (Hereinafter referred to as Fe-Mn oxide) layer composition.Oxygen isotope temperature measurement of opal shows that the precipitation temperature of the innermost opal and barite layer is 68.5 ℃, while the sub-inner long rod-shaped opal layer is 39.6 ℃, with (Eu / Eu *, Ce / Ce * and (La / Yb) N) and the Sr isotope ratios of Fe-Mn oxides extracted from the chimney walls of different layers All showed obvious anomalies in the outer epidermis, suggesting that the outermost layer was the outermost layer of the outermost layer of the chimney body during the initial stage of development.Morphological observations indicated that the microorganisms of the neutrophilic Fe-oxidizing bacteria and some of the possible use of Si Microorganisms play an important role in the construction of the chimney and their metabolic activity The formation of Fe-Si-type filament and a small amount of opal and barite precipitation formed the first ring-shaped original outer wall, and with the late rod-shaped opal together into a three-dimensional network, through the gradual mineralization of the proliferation of chimneys Finally, the mixing ratio of seawater and hydrothermal fluids is controlled, resulting in the formation of ring-like structures in the Si-rich chimney body. Elemental geochemical analysis also shows that the mineralogical characteristics of the annulus and the Fe-Mn oxides The “adsorption” of elements in the surrounding water controls the geochemical characteristics of the chimney body.