中国东北地区显生宙岩浆作用和洋-陆格局及其与气候演变的关系SCIEI北大核心CSCD

显生宙期间,地球经历了温室-冰室气候的周期性交替变化。在数百万年的时间尺度,这种古气候的转变被认为是碳源和碳汇过程耦合的结果,但一直以来关于两者贡献程度的认识尚不明确。通过全球统计分析,不同学者提出大陆弧火山脱气模型和热带弧-陆碰撞模型用于解释整个显生宙古气候的演变,分别强调了碳源和碳汇的一级控制作用。为了检验上述模型,更好地理解古气候的转变机制和演化细节,本文系统总结了中国东北地区显生宙岩浆作用-矽卡岩型矿床的时空展布和构造背景,以及弧-陆碰撞的时代、规模和古地理位置,通过数据统计和作图对比,发现东北地区岩浆作用-矽卡岩成矿峰期、弧-陆碰撞缝合带的时空迁移与大气圈CO_(2)浓度和大陆冰川沉积有很好的对应关系,暗示东北显生宙构造-岩浆过程和古气候演变的内在联系。综合东北地区及全球的研究进展,本文提出如下倾向性认识:1)洋-陆俯冲过程中火山-变质脱气的强度决定了CO_(2)排放量,而热带区域弧-陆碰撞缝合带的规模决定了全球硅酸盐风化速率和CO_(2)吸收量,在地质演化过程中两者紧密联动,共同控制了显生宙古气候的演变;2)大陆弧岩浆作用的全球爆发不一定能造成温室气候的出现,如果缺乏充分矽卡岩变质脱碳反应,大陆弧CO_(2)排放通量与岛弧、大洋中脊和板内并无显著区别;3)SO_(2)属于短期效应气体,理论和实例研究均暗示爆发式火山作用难以诱发大冰期的形成,火山作用之于长期气候应该仍是促使地球升温而非变冷。

Phanerozoic magmatism and ocean-continent framework of northeastern China and their relationship with climate change

Through the Phanerozoic Eon, Earth''s climate has varied between greenhouse and icehouse states. On multimillion-year time scales, the paleoclimate change has been considered to be the coupled result of carbon dioxide sources and sinks, but it is still unknown about their degree of contribution to transitions between these background climate states. According to global statistical analysis, variations in continental volcanic arc emissions and tropics arc-continent collisions are hypothesized to account for the Phanerozoic climate change, and different models emphasize a first order role of carbon sources and carbon sinks, respectively. In order to test the above models and better understand the transition mechanism and evolutionary details of paleoclimate, this paper systematically summarizes the temporal-spatial distribution and tectonic settings of Phanerozoic magmatism-skarn deposits, as well as the age, scale and paleogeographic position of arc-continent collisional sutures within Northeast (NE) China. Data statistics and chart comparison of NE China show strong correlations among the magmatic and skarn metallogenic peaks, the temporal-spatial variations of arc-continent collisional sutures, the extent of glaciation, and the atmospheric CO₂ levels, implying a genetic relationship between Phanerozoic tectono-magmatic processes of NE China with global paleoclimate change. Integration with the pre-existing worldwide results, we propose the following tendentious views: 1) the extent of volcanic-metamorphic outgassing during oceanic-continental subduction determines CO₂ emissions, while the scale of arc-continent collisional sutures within the tropics controls global weatherability and thus determines CO₂ consumption. Both of them are closely linked over geological history, and together control the Phanerozoic paleoclimate change; 2) global eruptions of continental arc magmatism do not necessarily result in a greenhouse climate. In the absence of adequate skarn-induced metamorphic decarburization, the CO₂ emission flux of continental arcs is not significantly different from that of island arcs, mid-ocean ridges and intraplates; 3) SO₂ is a short-term effect gas, and both theory and case studies suggest that explosive volcanisms are difficult to induce the formation of the Great Ice Age. Volcanic eruptions should still be contributing to the warming of the earth rather than cooling in long-term climate.