Iron speciation in bleached rocks by hydrocarbon leaching in Dushanzi Mud Volcano, NW China

Abstract

Abstract. Mud volcano is a typical petroleum leaching system, which normally result in bleaching effect to surrounding rocks. The result of Mössbauer spectroscopy of rock samples collected from the Dushanzi mud volcano system revealed clear variations in iron species. Compared to the unbleached reddish sedimentary rocks, the bleached rocks are dominated by reducing iron species such as paramagnetic ferrous iron (para-Fe 2+ ), ferrous iron in siderite (sid-Fe 2+ ), sulphide and pyrite (pyr-Fe 2+) whereas the original reddish rock is enriched in ferric iron including iron in hematite (hem-Fe 3+ ) and paramagnetic ferric iron (para-Fe 3+ ). A reduction of ferric iron species and hydrolysis of iron along with oxidation of hydrocarbons should be one of the main processes along bleaching by hydrocarbons to rocks.

57Fe Mössbauer spectroscopy study of sediments collected from test wells drilled in the Bikaner–Nagaur basin

“…Further in clay minerals also iron was dominantly present in the form Fe 2+ but oxide phases were meagerly present. Result obtained by us and by MØrup et al was further strengthened by study recently reported in literature on Mud-Volcanic samples [7].…”

CH4and CO2Emissions From Mud Volcanoes on the Southern Margin of the Junggar Basin, NW China: Origin, Output, and Relation to Regional Tectonics

“…The Yanshanian and Himalayan movements created four ESE‐WNW compress‐shear fold belts in the Tianshan foreland. From south to north these are (I) Qingshuihe‐Qigu, (II) Huoerguosi‐Manasi‐Tugulu, (III) Dushanzi‐Anjihai, and (IV) Xihu (Dai et al, ; Zheng, Fu, Kuno, & Matsuo, ; Zheng, Fu, Takahashi, et al, ). Several parallel thrust faults intersect these fold zones, which have provided the focus for 10 large historic earthquakes ( M S ≥ 5.0).…”

“…The Anjihai (AJH), Dushanzi (DSZ), Baiyanggou (BYG), and Aiqigou (AQG) mud volcanoes are located on the cores of anticlines in three reverse fault/fold belts with different intensities of activity on the southern margin of the Junggar Basin, NW China (Dai et al, ; Zheng, Fu, Takahashi, et al, ; Zheng, Fu, Kuno, & Matsuo, ). There have been sporadic reports of gas emissions from these mud volcanoes.…”

Mineralosphere Microbiome Leading to Changed Geochemical Properties of Sedimentary Rocks from Aiqigou Mud Volcano, Northwest China

“…Among them, the color change of sedimentary rocks is widely regarded as a good indicator of their depositional environments, diagenesis, and weathering history [ 8 ]. Surface seepage of geological fluids, such as crude oils and natural gases from mud volcanoes can transform the color of rocks from bright reddish to green, deep gray, or black, and is known as the bleaching effect [ 7 , 9 ]. The bleaching of rocks surrounding mud volcanoes indicates multiple organic–inorganic interactions occurring within fluids, leading to complex chemical reactions between the geological fluid itself and the surrounding minerals [ 1 ].…”