Lucai et al.-EPSL: 720 million years ago in the launch of the magma rock province and snowball earth

Abstract: South China newly determined a province of Magnolia Rock in the middle latitude when the formation of 720 million years ago, and the magma province that was similar to the time when it was reported was at a low latitude. These magma activities that expand from low latitude tropical to mid -latitude temperature and span Rodinia's oversized continent, from about 720 million years ago to the Sturtian Ice period (717 million years ago), may be related to the super continental super mantle column It is also closely related to the start of Sturtian Snowball Earth.

In the ancient New Yuan Dynasty, 72-635 billion years ago, the surface system has experienced the two "snowball Earth" incidents of Sturtian (717-660ma) and Marinoan (650-635ma). Almost the entire earth was wrapped in ice and snow. The cause and influence of this extreme climate is one of the cutting -edge hotspots for the continuous attention of academic circles.

The Franklin fire of about 720 mA in North America erupted the stratum near the ancient equator, invading the rich sulfur, and the time at the time of the starting time of Sturtian snowball (Figure 1). Therefore, it is considered to induce the start of the Sturtian ice period, which includes two representative models: "volcanic winter" and "base rock wind". The former believes that the cold background of the inferred reducing the height of the top of the streaming layer near the equator, prompting the erupting SO2 eruption of Franklin in the same ice period can "smoothly" into the flat stratum, resulting in a sudden increase in the counter -photos of the planet and causing global cooling. The latter believes that the large -scale base lava generated by Franklin's fire into the province is strongly weathered, which has promoted the drop in the greenhouse gas CO2 in the atmosphere to a threshold that can promote snowball. However, the numerical simulation found that the total area of ​​the province of fire into the province of the rock or its relationship between the area between the tropical area and the ice cover of the mainland. Can Franklin's fire province be launched alone? How to build a cold background through geological evidence to inject the linked stratosphere with SO2 eruption SO2 in the same ice period? These questions have not yet received a good answer.

Figure 1 Sturtian icing period, the ancient geographical distribution of 720 mA magmatic rock province and the summary of the age, Franklin fire into the geomyochemical space province

In addition to the Franklin fire in North America, other continents may also develop large-scale magma activities that are stretched-into the turning period of the ice (Figure 1). Studies based on fine -grained rocks and ND concentrations have found that before the Sturtian Ice period, the debris component contributed by the weathering of the base source area was> 80%, implying that South China was likely to develop more at that time. Large -scale basic magma activity. Therefore, the time-spatial distribution of the time-to-see-the rotary period of the Rachel-the Tingling period is of great significance to the in-depth understanding of the starting mechanism of the Sturtian ice period.

Based on the above problems and ideas, Academician Li Xianhua team and collaborators of the Institute of Geology and Earth Physics of the Chinese Academy of Sciences, through comprehensive research on high -precision age and full rock geochemistry, identified a fire with Franklin in the South Qinling area northern China to become a fire with Franklin. The magma incident similar to the times is called Hubei-Shaanxi Magnolia Stone Province (Figure 1 and Figure 2). The main spray time of this magma rock province is 720.21 ± 0.32 ma, which starts about 3 million years (Figure 1b and Figure 2) at the Sturtian ice period (Figure 1b and 2). The distribution area is at least 0.1 mkm2 (Figure 2A). Spraying rocks and invasive rocks. Comprehensive research on geological, rock combination, and global chemistry showed that (Figure 3), Hubei-Shaanxi magma rock province was formed in a typical continental cracking environment; Xuanwu magma comes from different depth of soft flow mantle. Neutral rocks with Xuanwu Rocks; the basic magma invaded at the same time provides heat sources, causing the crust to form a related streaming rock.

Figure 2 The characteristic and time-empty distribution characteristics of the South China 720 MA magma province. The age error is ± x/y/z, x is the analysis error, Y includes the correction error of x and tracer, Z to Y plus 238U decay constant error error error error

Comprehensive analysis of high-precision schools, ancient geography and geochemical data shows that (1) Wide-wide magma activity starts from ~ 720mA to the Sturtian ice period; Expansion from the equator to the middle latitude region (Figure 1A); (3) Hubei-Shaanxi Magnolia Rock Province and Lawren Siberia's high-end rock province have a comparison of the characteristics of the earth chemical composition (Figure 4). In view of the consistency of the age of magma activity and the chemical composition, the wide range of spatial distribution, and the record of the Franklin mantle column, these ～ 720-717ma magma can be explained with the Rodinia super continental mantle column (Figure 1) Essence In addition, the study also proposed that the low-mid-latitude volcano that happened before the Sturtian Ice period may enhance the global weathering, create a cold background climate, reduce the height of the top of the streaming layer near the equator, and promote the fire of Franklin in the same ice. The eruption of SO2 "smoothly" into the flat flow layer. This chain reaction may eventually cause the start of Sturtian Snowball Earth.

Figure 3 South China 720 MA Magnarous Rock Province Geochemical Characteristics

Figure 4 Franklin, IRKUTSK, and Hubei-Shaanxi Magnarous Rock Provincial Gelastic Rock (showing the inner and outer bands of Geochemical inner chemistry in Franklin magma rocks; IRKUTSK and Hubei-Shaanxi magmatic rock provinces with ge chemical chemistry and chemistry Based on Franklin Magnarous Rock Province) Hubei-Shaanxi magmatic rock province, which is newly identified in South China, has broaden the understanding of the time and space distribution of the stretch of stretching-into the transition of the stretch-into the transition period. In this study of geological evidence, the cold background climate in front of the Sturtian Snowball Earth is associated with the same ice -stratified air -soluble oscillator, providing a complete snowball earth launch mechanism.

Research results published in international academic journals EPSL (Lu K (Lukai), Mitchell R N, Yang C* (Yang Chuan), zhou j L (Zhou Jiulong), wu l g (Wu Liguang), wang x c Li Xianhua). WideSpream Magmatic Provinces at the Onset of the Sturtian Snowball Earth [J]. Earth and Planetary Science Letters, 2022, 594: 117736. Doi: 10.1016/J.EPSL.2022.173.1773.1773.1773.173.1773.173.173.173.173.173.173.173.173.173.173.173.173.173.11773.11773.1173.11773.1173.1173.1173.1173.1173.1173.1173.1173.1173. Study under the National Key R & D Planning Project "New Technologies for Transformation of Mineral Studies" (2018YFA0702600), the Strategic Pioneer Class B (XBD18030301) of the Chinese Academy of Sciences, and Key Research Projects ( IGGCAS-201905) joint funding.

Beautiful editor: Chen Feifei

School pair: Wanpeng

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