Geochemistry of Darwin glass and target rocks from Darwin crater, Tasmania, Australia
Geochemistry of Darwin glass and target rocks from Darwin crater, Tasmania, Australia
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澳大利亚塔斯马尼亚达尔文陨石坑的达尔文玻璃和目标岩石的地球化学
DOI：
10.1111/j.1945-5100.2008.tb00667.x
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发表时间：
2008
影响因子：
2.2
通讯作者：
K. Howard
中科院分区：
文献类型：
--
作者：
K. Howard
达尔文玻璃形成于大约80万年前的澳大利亚塔斯马尼亚西部。达尔文陨石坑的目标岩为石英岩和板岩（Siluro -泥盆系，Eldon群）。分析表明，玻璃分为2组，平均组1由SiO2（85%）、Al2O3（7.3%）、TiO2（0.05%）、FeO（2.2%）、MgO（0.9%）和K2O（1.8%）组成。第2组SiO2平均值较低（81.1%），Al2O3平均值较高（8.2%）。组2富集FeO（+1.5%）、MgO（+1.3%）和Ni、Co、Cr，组2平均Ni （416 ppm）、Co （31 ppm）、Cr （162 ppm）超出了沉积岩的范围。玻璃岩与靶岩的REE模式一致（La/Lu = 5.9 ~ 10, Eu/Eu* = 0.55 ~ 0.65），微量元素丰度重叠。玻璃的87Sr/86Sr比值（0.80778-0.81605）落在岩石样品定义的范围（0.76481-1.1212）内。ε‐Nd结果范围为-13.57 ~ -15.86。Nd模型年龄范围为1.2-1.9 Ga (CHUR)，玻璃（1.2-1.5 Ga）落在目标样品定义的范围内。87Sr/86Sr / 87Rb/86Sr的回归年龄（411±42 Ma）和初始比值（0.725±0.016），以及43Nd/144Nd的初始比值（0.51153±000011）和回归年龄（451±140 Ma）表明，该玻璃具有继承达尔文陨石坑靶岩的同位素信号。使用目标岩石成分的混合模型成功地模拟了除FeO、MgO、Ni、Co和Cr组2之外的所有元素的玻璃。使用陆地超镁铁质岩石的混合模型不能与玻璃成分匹配，这些富集可能与抛射物有关。
Abstract— Darwin glass formed about 800,000 years ago in western Tasmania, Australia. Target rocks at Darwin crater are quartzites and slates (Siluro‐Devonian, Eldon Group). Analyses show 2 groups of glass, Average group 1 is composed of: SiO2 (85%), Al2O3 (7.3%), TiO2 (0.05%), FeO (2.2%), MgO (0.9%), and K2O (1.8%). Group 2 has lower average SiO2 (81.1%) and higher average Al2O3 (8.2%). Group 2 is enriched in FeO (+1.5%), MgO (+1.3%) and Ni, Co, and Cr. Average Ni (416 ppm), Co (31 ppm), and Cr (162 ppm) in group 2 are beyond the range of sedimentary rocks. Glass and target rocks have concordant REE patterns (La/Lu = 5.9–10; Eu/Eu* = 0.55–0.65) and overlapping trace element abundances. 87Sr/86Sr ratios for the glasses (0.80778–0.81605) fall in the range (0.76481–1.1212) defined by the rock samples. ε‐Nd results range from –13.57 to –15.86. Nd model ages range from 1.2–1.9 Ga (CHUR) and the glasses (1.2–1.5 Ga) fall within the range defined by the target samples. The 87Sr/86Sr versus 87Rb/86Sr regression age (411 ± 42 Ma) and initial ratio (0.725 ± 0.016), and the initial 43Nd/144Nd ratio (0.51153 ± 000011) and regression age (451 ± 140 Ma) indicate that the glasses have an inherited isotopic signal from the target rocks at Darwin crater. Mixing models using target rock compositions successfully model the glass for all elementsexcept FeO, MgO, Ni, Co, and Cr in group 2. Mixing models using terrestrial ultramafic rocks fail to match the glass compositions and these enrichments may be related to the projectile.
澳大利亚塔斯马尼亚州西部达尔文陨石坑的地质
影响因子：
5.3
作者：
Howard K
通讯作者：
Howard K