One billion years of Archean history, Pilbara Craton, Western Australia

The Pilbara is an important region for the study of early Earth history, primarily because it contains large areas of volcanics and sediments, as old as 3550 million years, that are commonly extremely well preserved as a result of an exceptionally heterogeneous tectonic overprint during cratonisation. This latter event was completed by 2800 million years ago and hence much of the cover sequence up to the classic Hamersley banded iron formation is Archean in age.     

Astronomical frequencies for pre-Quaternary palaeoclimate studies

The sensitivity of the Earth's orbital frequencies, involved in the astronomical theory of palaeoclimates, to the Earth-Moon distance and consequently to the length of the day and to the dynamical ellipticity of the Earth has been investigated for the last billion years. The shortening of the Earth-Moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for the obliquity and the precession, a shortening which is larger for the longer periods. These periods of precession and obliquity influenced by the changing Earth-Moon distance, length of the day and dynamical ellipticity of the Earth, have been recomputed for the last 440 million years.     

Tholeiitic and Alkaline Basaltic Lavas of Wang-Tian’e and Changbaishan Volcanoes (Northeastern China): Timing and Genetic Relationship

Doklady Earth Sciences - Changbaishan and Wang-Tian’e volcanoes of Changbaishan area (Northeast China) were formed with a slight time gap in the last four million years. Wang-Tian’e...     

21世纪地球科学研究的重大科学问题

凝炼地球科学研究的重大科学问题,对推动地球科学基础研究的发展具有重要意义。美国国家研究理事会（National Research Council）2008年3月发布的研究报告《地球的起源和演化：变化行星的研究问题》提出了21世纪固体地球科学研究的10个重大科学问题：①地球和其他行星的起源;②地球早期的演化历史;③生命的起源;④地球内部的运动及其对地表的影响;⑤地球的板块构造与大陆;⑥地球的物质特性对地球过程的控制;⑦气候变化的原因与幅度;⑧地球—生命的相互作用;⑨地震、火山喷发等灾害及其后果的预测;⑩地球内外流体运动对人类环境的影响。这些重大科学问题对我国的地学发展战略研究及地球科学基础研究均将具有重要的借鉴和指导意义。主要依据NRC的《地球的起源和演化：变化行星的研究问题》报告,对这些重大科学问题进行了解读和分析。     

The Deep Submerged Continental Crust: The Central Arctic and Zealandia in the Southwest Pacific

Doklady Earth Sciences - A vast area of up to five million square kilometers is located in the Pacific Ocean to the east of Australia. The Earth’s crust up to 10–23 km thick is...     

扬子西南缘古元古界亮山组圆盘状化石的发现及其环境意义

通过1:5万区域地质调查研究,首次在滇中易门地区古元古界易门群亮山组发现圆盘状宏体化石,进一步丰富了滇中古元古代早期宏体化石群种类,为扬子西南缘前寒武纪地层大区域对比提供古生物依据.本次的初步报道为从不同角度探索距今2.8～0.8 Ga的地球早期发展、演化历史开启了新窗口;对地球早期的环境演化与生命进化的研究具有重要价...     

The magma-to-mud cycle

For more than 3700 million years of Earth history, the magma-to-mud cycle has steadily generated new crustal rock. Mud formed by rock weathering coats the Earth's surface and helps to sustain life. Reactive clay minerals are the key components of mud, and control the absorption and release of chemicals and fluids that are critical for the recycling of crustal rocks.     

Reconciling the Earth's stratigraphic record with the structure of our galaxy

The passage of our Solar System through the spiral arms has been implicated as a contributor to global environmental perturbations.The suggestion of a consistent structure within the arms,informed by density wave theory,raises the possibility of repeating patterns of events at each arm crossing.Here we test the hypothesis that the structure of the arms of our galaxy influences the stratigraphic record on Earth.We construct independent structural and temporal models and colbine these to compare the timings of arm tracers,materials from the earliest Solar System and events on Earth,including the largest extinctions.We find that a recurring sequence of events across the four arms emerges with an average arm-passing time of 188 million years.We suggest that the multiple temporal overlaps of events across arms,and their alignment with arm tracers and the earliest Solar System,presents an opportunity for a greater understanding of both Earth-based phenomena and galactic structure.     

Amino acid racemization in amber-entombed insects: implications for DNA preservation

DNA depurination and amino acid racemization take place at similar rates in aqueous solution at neutral pH. This relationship suggests that amino acid racemization may be useful in accessing the extent of DNA chain breakage in ancient biological remains. To test this suggestion, we have investigated the amino acids in insects entombed in fossilized tree resins ranging in age from <100 years to 130 million years. The amino acids present in 40 to 130 million year old amber-entombed insects resemble those in a modern fly and are probably the most ancient, unaltered amino acids found so far on Earth. In comparison to other geochemical environments on the surface of the Earth, the amino acid racemization rate in amber insect inclusions is retarded by a factor of >10(4). These results suggest that in amber insect inclusions DNA depurination rates would also likely be retarded in comparison to aqueous solution measurements, and thus DNA fragments containing many hundreds of base pairs should be preserved. This conclusion is consistent with the reported successful retrieval of DNA sequences from amber-entombed organisms.     

Radiogenic trigger and driver for continental rifting and initial ocean spreading

Closure and opening of oceans on time‐scales of a few hundred million years is a fundamental tectonic process on Earth, typically referred to as a “Wilson cycle”. Subduction of oceanic and continental crust leading up to and during continent–continent collision can refertilize and enrich the orogenic continental lithospheric mantle in heat‐producing elements. The resulting thermal anomaly weakens the lithosphere and, along with structural weaknesses (e.g. sutures), make this orogenic lithosphere more prone to rifting given an extensional stress field. Thermal modelling shows that anomalously hot lithosphere can focus asthenospheric upwellings over time‐scales of a few hundred million years. Processes related to closure of oceans thus provide a mechanism for later localization of rifting and an extensional driving force.     

冰雪地球的研究进展综述

在大约6~7亿年前的新元古代时期，地球是否曾经被冰雪完全覆盖而成为了一个“冰雪地球”？如果是，什么诱发了这种全球性的冰川期？又是什么导致了它的融化？新元古代时期的极端气候变化对其后的寒武纪生命大爆发有何影响？围绕这些问题，古地质、古生物和古气候学界在最近几年展开了广泛的研究和激烈争论。根据现有的研究结果，地球在新元古代时期确实经历了数次地球历史上最为严重的全球性冰川期，但地球是否被完全冰封还需要更充分的古地质和古生物方面的证据来证明；利用气候模式对各种可能的外部强迫的模拟试验表明“冰雪地球”是很难形成的，并且，如果地球进入完全被冰封的状态，它将是难以被融化的；关于新元古代时期剧烈的气候变化对寒武纪生命大爆发所起的作用存在2种观点，一种认为气候变化导致了原始生命的基因突变并诱发了寒武纪生命爆发，另一种认为这种影响主要是生态方面的。     

The Navajo Sandstone

The Navajo Sandstone is the remnant of an early Jurassic (Pliensbachian-Toarcian) aeolian (wind-blown) system that stretched over most of the western United States for several million years. Interpretation of these deposits suggests that the Navajo erg (sand sea) was one of the most extensive desert systems ever to have existed in the history of the Earth, and probably contained the largest sand dunes that have ever moved across the surface of the planet.     

Deep mantle roots and continental emergence: implications for whole-Earth elemental cycling,long-term climate,and the Cambrian explosion

Elevations on Earth are dominantly controlled by crustal buoyancy, primarily through variations in crustal thickness: continents ride higher than ocean basins because they are underlain by thicker crust. Mountain building, where crust is magmatically or tectonically thickened, is thus key to making continents. However, most of the continents have long passed their mountain building origins, having since subsided back to near sea level. The elevations of the old, stable continents are lower than that expected for their crustal thicknesses, requiring a subcrustal component of negative buoyancy that develops after mountain building. While initial subsidence is driven by crustal erosion, thermal relaxation through growth of a cold thermal boundary layer provides the negative buoyancy that causes continents to subside further. The maximum thickness of this thermal boundary layer is controlled by the thickness of a chemically and rheologically distinct continental mantle root, formed during large-scale mantle melting billions of years ago. The final resting elevation of a stabilized continent is controlled by the thickness of this thermal boundary layer and the temperature of the Earth’s mantle, such that continents ride higher in a cooler mantle and lower in a hot mantle. Constrained by the thermal history of the Earth, continents are predicted to have been mostly below sea level for most of Earth’s history, with areas of land being confined to narrow strips of active mountain building. Large-scale emergence of stable continents occurred late in Earth’s history (Neoproterozoic) over a 100–300 million year transition, irreversibly altering the surface of the Earth in terms of weathering, climate, biogeochemical cycling and the evolution of life. Climate during the transition would be expected to be unstable, swinging back and forth between icehouse and greenhouse states as higher order fluctuations in mantle dynamics would cause the Earth to fluctuate rapidly between water and terrestrial worlds.     

新星云假说下地球扁率变化上限及影响因素

地球的形状变化是地球演化研究的基本问题之一。为了确定地球形状的变化需要了解各个地质历史时期地球扁率的变化。根据位场球函数理论导出地球的扁率公式,研究扁率与地球的半径、质量和角速度的关系。基于新星云假说推测地球的半径、质量和角速度的变化量,计算出地球在各个时期的扁率并作为上限并画出曲线,各地质历史时期中地球扁率的真实值应该小于计算的扁率值。地球的扁率自地球形成以来脉动变化的情况下总体趋势在减小。影响地球扁率的因素有平均半径、质量和角速度,分析发现地球形成后5亿年为时间起点计算,到现在(共41亿年)为止平均半径变化对扁率的总影响约为3%,质量变化的总影响没有超过百万分之三。而角速度的减小对扁率变化的贡献超过97%。地球扁率共减少了74.3%。     

硅质海绵骨针矿化机制及仿生应用研究进展

硅质海绵动物是地球上最简单、最古老的多细胞动物,它经几百万年的自然进化成就了适应自然和接近完美的技术蓝图,为人类利用纳米生物技术仿生合成生物无机矿物材料提供了一种崭新的节能和"环境友好"技术,在光纤、微电子和生物医学材料等领域具有广阔的仿生应用前景.生长在深海1000 m以下水深的单根海绵动物的根须骨针长达3 m,是世...     

The split fate of the early Earth,Mars, Venus,and Moon

Plate tectonics shaped the Earth, whereas the Moon is a dry and inactive desert, Mars probably came to rest within the first billion years of its history, and Venus, although internally very active, has a dry inferno for its surface. Here we review the parameters that determined the fates of each of these planets and their geochemical expressions. The strong gravity field of a large planet allows for an enormous amount of gravitational energy to be released, causing the outer part of the planetary body to melt (magma ocean), helps retain water on the planet, and increases the pressure gradient. The weak gravity field and anhydrous conditions prevailing on the Moon stabilized, on top of its magma ocean, a thick buoyant plagioclase lithosphere, which insulated the molten interior. On Earth, the buoyant hydrous phases (serpentines) produced by reactions between the terrestrial magma ocean and the wet impactors received from the outer solar system isolated the magma and kept it molten for some few tens of million years. The planets from the inner solar system accreted dry: foundering of wet surface material softened the terrestrial mantle and set the scene for the onset of plate tectonics. This very same process also may have removed all the water from the surface of Venus and added enough water to its mantle to make its internal dynamics very strong and keep the surface very young. Because of a radius smaller than that of the Earth, not enough water could be drawn into the Martian mantle before it was lost to space and Martian plate tectonics never began. The radius of a planet is therefore the key parameter controlling most of its evolutional features.     

Long-term electromagnetic core–mantle coupling and the Earth’s rotation acceleration in the Mesozoic Era

Growth lines in the mineralized tissues of living and fossil organisms often exhibit regular patterns that record daily, monthly, or annual cycles. Growth laminations in fossil corals and other marine invertebrates indicate long-term deceleration of the Earth’s rotation, probably largely due to tidal friction, resulting in a decline in the number of days per year over the Earth’s history. Fossils suggest the rate of decline has not been uniform, with the trend between the late Carboniferous and Cretaceous in particular departing from preceding and subsequent periods. However, insufficient data have obscured the nature and cause of the apparent halt in despinning within this time interval. Here we present new fossil geochronometer data that reveal a sustained acceleration in the Earth’s rotation in the early Mesozoic Era, lasting about 90 million years and producing a decrease in the length of day (LOD) at an average rate of about 3 ms/cy. The coincidence of this acceleration with certain geophysical events including the final assembly of Pangaea and a change in the intensity and stability of the geomagnetic field strongly suggests that its cause is rooted in the deep interior of the Earth. A similar explanation has been proposed for observed decadal variations in the Earth’s rotation. Our results suggest large-scale linkage of rotational variation, tectonics, and the geomagnetic field to core–mantle boundary (CMB) dynamics. Furthermore the newly identified acceleration in the Earth’s rotation which began at the end of the Paleozoic, and the geophysical factors that are associated with it, can ultimately bear on the causal mechanisms behind the Permo-Triassic mass extinction.     

New W-isotope evidence for rapid terrestrial accretion and very early core formation

The short-lived ¹⁸²Hf-¹⁸²W-isotope system is an ideal clock to trace core formation and accretion processes of planets. Planetary accretion and metal/silicate fractionation chronologies are calculated relative to the chondritic ¹⁸²Hf-¹⁸²W-isotope evolution. Here, we report new high-precision W-isotope data for the carbonaceous chondrite Allende that are much less radiogenic than previously reported and are in good agreement with published internal Hf-W chronometry of enstatite chondrites. If the W-isotope composition of terrestrial rocks, representing the bulk silicate Earth, is homogeneous and 2.24 ε_182W units more radiogenic than that of the bulk Earth, metal/silicate differentiation of the Earth occurred very early. The new W-isotope data constrain the mean time of terrestrial core formation to 34 million years after the start of solar system accretion. Early terrestrial core formation implies rapid terrestrial accretion, thus permitting formation of the Moon by giant impact while ¹⁸²Hf was still alive. This could explain why lunar W-isotopes are more radiogenic than the terrestrial value.     

新元古代晚期盖帽碳酸盐岩的成因与“雪球地球”的终结机制

新元古代晚期约635 Ma的地球发育了到达赤道附近的冰川作用，地质记录上表现为代表寒冷气候的冰期沉积杂砾岩，直接被代表温暖环境的碳酸盐岩层（常称盖帽碳酸盐岩）覆盖。由于盖帽碳酸盐岩奇特的岩石学和地球化学特征，引起了对其成因认识的巨大争论，提出了“雪球地球”和“甲烷渗漏”等假说。“雪球地球”假设可以解释一些令人困惑的地学现象，如低纬度和低海拔冰川沉积、盖帽碳酸盐岩、碳酸盐δ13C负漂移和条带状铁矿层等，但许多科学家对此提出了质疑。最近对盖帽碳酸盐岩的δ13C分析结果（最低达-41‰）、盖帽碳酸盐岩发育的类似现代冷泉碳酸盐岩沉积组构等似乎支持“甲烷渗漏”假说。     

Low energy trajectories for the Moon-to-Earth space flight

The Moon-to-Earth low energy trajectories of ‘detour’ type are found and studied within the frame of the Moon-Earth-Sun-particle system. These trajectories use a passive flight to the Earth from an initial elliptic selenocentric orbit with a high aposelenium. The Earth perturbation increases the particle selenocentric energy from a negative value first to zero and then to a positive one and therefore leads to a passive escape of the particle motion from the Moon attraction near the translunar libration pointL ₂. This results in the particle flight to a distance of about 1.5 million km from the Earth where the Sun gravitation decreases the particle orbit perigee distance to a small value that leads to the particle approaching the Earth vicinity in about 100 days of the flight. A set of the Moon-to-Earth ‘detour’ trajectories is defined numerically. Characteristics of these trajectories are presented. The ‘detour’ trajectories give essential economy of energy (about 150 m/s in Delta V) relative to the usual ones.