The Neoproterozoic "Blood Falls" in Tarim Craton and Their Possible Connection With Snowball Earth. Issue 1 (28th January 2019)

• Record Type: Journal Article
• Authors: Gao, B. F.; Wu, C. Z.; Yang, T.; Santosh, M.; Dong, L. H.; Zhao, T. Y.; Ye, H.; Lei, R. X.; Li, W.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 1(2019)
• Page Start: 229
• Page End: 244
• Publication Date: 2019-01-28
• Subjects: Neoproterozoic glaciation -- Blood Falls -- Snowball Earth -- Fe isotope -- oxygen isotope -- Tarim; Geomorphology -- Periodicals; 551.3
• DOI: 10.1029/2018JF004862
• Languages: English
• ISSNs: 2169-9003

Abstract

Abstract: Blood Falls refers to the outflow of iron‐rich brine plumes under the Taylor Glacier in Antarctica, which have distinctive blood‐like red color. It was proposed that during the Cryogenian, Fe oxides of terrestrial origin accumulated under glaciers via a mechanism similar to the modern Blood Falls, although reports of iron deposits of such novel origin are lacking in literature. The Quruqsay iron formation is hosted in Neoproterozoic glacial sequences in the northern margin of the Tarim Craton in NW China and consist of 15 lenticular iron orebodies. The iron ores are mainly composed of fine Fe‐oxide aggregate and clastics, with the latter sometimes occurring as dropstones indicating glacial fluvial deposition. The hematite minerals show positive Ce and Y anomalies but lack positive Eu anomalies, with flat shale‐normalized rare Earth elements patterns. The hematite minerals also display remarkably negative ε Nd values and close‐to‐0 δ 56 Fe values, which collectively indicate that iron was sourced from continents rather than mid‐ocean ridge hydrothermal vents. Additionally, δ 18 O values of the hematite are consistent with the large ice‐volume during the Snowball Earth event. Evidence from the Quruqsay iron deposit suggest oxidation of terrestrial sub‐glacier iron‐bearing discharge in oceans of extensive glaciation, correlating with the predicted Blood Falls‐type iron deposits in the Neoproterozoic. The Quruqsay iron formation is a unique hematite‐rich iron deposit implying that subglacial lakes can be a significant repository for Fe 2+ and that the volume of the Neoproterozoic glaciers may be much higher than the current glacier. Plain Language Summary: Blood Falls refers to the red color outflow of iron‐rich brine plumes under the Taylor Glacier in Antarctica. During Cryogenian, a very cold Era of the Earth called "Snowball Earth event." A number of iron formation formed at this time, but most were developed in abysmal facies. Blood Falls near continental shelf is relatively rare. The Quruqsay iron formation is hosted in Neoproterozoic glacial sequences in the northern margin of the Tarim craton, NW China. Geological and geochemical features of the iron formation indicate oxidation of terrestrial sub‐glacier Fe‐bearing discharge in oceans during extensive glaciation, correlating with the predicted Blood Falls‐type iron deposits in the Neoproterozoic. According to oxygen isotope balance calculation between glacier, seawater and hematite, the volume of the Neoproterozoic glaciers is estimated to be several times larger than the current glacier. Key Points: The Cryogenian Quruqsay is a terrestrial subglacial iron formation formed through oxidation of glacial fluvial deposition The Neoproterozoic iron formation resembles "Blood Falls" iron‐rich brine plumes under the Taylor Glacier in Antarctica The global volume of Neoproterozoic glaciers is estimated to be 6–8 times larger than the current glacier volume