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首页> 外文期刊>The American mineralogist >Rates and styles of planetary cooling on Earth, Moon, Mars, and Vesta, using new models for oxygen fugacity, ferric-ferrous ratios, olivine-liquid Fe-Mg exchange, and mantle potential temperature
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Rates and styles of planetary cooling on Earth, Moon, Mars, and Vesta, using new models for oxygen fugacity, ferric-ferrous ratios, olivine-liquid Fe-Mg exchange, and mantle potential temperature

机译：使用新的氧逸度，铁-铁比，橄榄石-液态铁-镁交换和地幔势温度模型，对地球，月球，火星和维斯塔星上行星的冷却速率和样式进行了研究

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摘要

Mantle potential temperatures (T-p) provide insights into mantle circulation and tests of whether Earth is the only planet to exhibit thermally bi-modal volcanism-a distinctive signature of modem plate tectonics. Planets that have a stagnant lid, for example, should exhibit volcanism that is uni-modal with T-p, since mantle plumes would have a monopoly on the genesis of volcanism. But new studies of magmatic ferric ferrous ratios (x(Fe2O3)(liq)/x(Feo)(liq)) (Cottrell and Kelley 2011) and the olivine-liquid Fe-Mg exchange coefficient, K-D(Fe-Mg)(Ol-liq) (or K-D) (Matzen et al. 2011) indicate that re-evaluations of T-p are needed. New tests and calibrations are thus presented for oxygen fugacity (fo(2)), x(Fe2O3)(liq)/x(Feo)(liq), potential temperature (T-p), melt fraction (F), K-D, and peridotite enthalpies of fusion (Delta H-fus) and heat capacities (C-p). The new models for x(Fe2O3)(liq)/x(Feo)(liq) and fo(2) reduce error by 25-30%, and residual error for all models appears random; this last observation supports the common, but mostly untested, assumption that equilibrium is the most probable of states obtained by experiment, and perhaps in nature as well. Aggregate la error on T-p is as high as similar to +/- 77 degrees C, and estimates of F, and mantle olivine composition, are the greatest sources of error. Pressure and Delta H-fus account for smaller, but systematic uncertainties (a constant Delta H-fus, can under-predict T-excess = T-p(plume)-T-p(ambient) assumptions of 1 atm can under-predict T-p). However, assumptions about whether parental magmas are incremental, accumulated, or isobaric batch melts induces no additional systematic error. The new models show that maximum T-p estimates on the oldest samples from Earth, Mars, Moon, and Vesta, decrease as planet size decreases. This may be expected since T-p should scale with accretion energy and reflect the Clausius-Clapeyron slope for the melting of silicates and Fe-Ni alloys. This outcome, however, occurs only if shergottites (from Mars) are 4.3 Ga (e.g., Bouvier et al. 2009; Werner et al. 2014), and the highest MgO komatiites from Earth's Archean era (27-30% MgO; Green et al. 1975) are used to estimate T-p. With these assumptions, Earth and Mars exhibit monotonic cooling, and support for Stevenson's (2003) idea that smaller planets cool at similar rates (similar to 90-135 degrees C/Ga), but at lower absolute temperatures. Tp estimates for Mars and Earth are also important in two other ways: Mars exhibits non-linear cooling, with rates as high as 275-550 degrees C/Ga in its first 0.5 Ga, and Archean volcanism on Earth was thermally bi-modal. Several hundred Archean volcanic compositions are in equilibrium with Fo92-94 olivine, and yield Tp modes at 1940 and 1720 degrees C, possibly representing plume and ambient mantle, respectively. These estimates compare to modem T, values of 1560-1670 degrees C at Mauna Loa (plume) and 1330-1450 degrees C at MORB (ambient). We conclude that plate tectonics was active in some manner in the Archean, and that assertions of an Archean "thermal catastrophe" are exaggerated.
机译：地幔潜在温度（T-p）提供了有关地幔环流的见解，并检验了地球是否是唯一表现出热双峰火山作用的行星-这是现代板块构造学的独特标志。例如，盖子停滞的行星应该表现出与T-p单峰的火山作用，因为地幔柱将垄断火山作用的起源。但是新的岩浆三价铁比率（x（Fe2O3）（liq）/ x（Feo）（liq））（Cottrell和Kelley 2011）和橄榄石-液体Fe-Mg交换系数KD（Fe-Mg）（Ol）的新研究-liq）（或KD）（Matzen等人，2011年）指出，需要对Tp进行重新评估。因此，提出了关于氧逸度（fo（2）），x（Fe2O3）（liq）/ x（Feo）（liq），势能温度（Tp），熔体分数（F），KD和橄榄岩焓的新测试和校准熔合（Delta H-fus）和热容（Cp）。 x（Fe2O3）（liq）/ x（Feo）（liq）和fo（2）的新模型将误差降低了25％至30％，并且所有模型的残余误差似乎都是随机的。这最后一个观察结果支持了一个普遍但未经检验的假设，即平衡是通过实验获得的状态最可能的状态，也许在自然界也是如此。 T-p上的合计la误差高达+/- 77摄氏度，F的估计值以及地幔橄榄石成分是最大的误差来源。压力和Delta H-fus占了较小的但系统性的不确定性（恒定的Delta H-fus可能会低估T-excess = T-p（plume）-T-p（ambient）1 atm的假设会低估T-p）。但是，关于母体岩浆是增量岩浆，累积岩浆还是等压间歇熔体的假设不会引起其他系统误差。新模型表明，随着地球尺寸的减小，对来自地球，火星，月球和维斯塔的最古老样本的最大T-p估计值会减小。这是可以预期的，因为T-p应该随吸积能量成比例，并反映硅酸盐和Fe-Ni合金熔化的Clausius-Clapeyron斜率。然而，仅当（来自火星的）软锰矿为4.3 Ga（例如，Bouvier等人; 2009; Werner等人，2014），以及地球太古代时代MgO含量最高的锰铁矿（27-30％MgO; Green等）时，这种结果才会发生。等（1975年）被用来估计Tp。根据这些假设，地球和火星表现出单调冷却，并支持史蒂文森（2003）的想法，即较小的行星以相似的速率（类似于90-135摄氏度/加仑）冷却，但在较低的绝对温度下冷却。对火星和地球的Tp估算在另外两个方面也很重要：火星表现出非线性冷却，在最初的0.5 Ga中速率高达275-550 C / Ga，地球上的太古宙火山是热双峰的。数百个太古宙火山岩成分与Fo92-94橄榄石处于平衡状态，并在1940和1720摄氏度下产生Tp模式，可能分别代表羽状流和周围地幔。这些估计值与调制解调器T的值相比，在莫纳罗亚河（松木）的温度为1560-1670摄氏度，在MORB（环境温度）的温度为1330-1450摄氏度。我们得出的结论是，板块构造学在太古代中以某种方式活跃，并且夸大了太古代的“热灾难”的主张。

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