Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy.
Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy.
复制标题
DOI：
10.1126/sciadv.aap8306
复制
发表时间：
2018-05
期刊：
影响因子：
13.6
通讯作者：
Smith CL
中科院分区：
文献类型：
--
作者：
Cassata WS;Cohen BE;Mark DF;Trappitsch R;Crow CA;Wimpenny J;Lee MR;Smith CL
火星陨石NWA 7034的变质历史表明，火星地壳的二分法可能在行星形成的1亿年内形成。火星陨石西北非洲（NWA）7034和它的配对石头是唯一来自火星的角砾风化层样本，其成分代表了平均火星地壳。因此，这些样品提供了一个独特的机会，以限制变质和蚀变的过程中，火星地壳，我们已经通过U-Pu/Ar，40 Ar/39 Ar，和U-Th-Sm/He测时法进行了调查。U-Pu/Pb年龄与先前报道的NWA 7034获得的Sm-Nd和U-Pb年龄相当，并确认了源岩的古老（> 43亿年）年龄。经过近30亿年（马）的平静，源地形经历了数亿年的热变质作用记录的K-Ar系统，似乎有不同的空间和时间。这种持久的变质作用与地幔柱相关的岩浆作用是一致的，并表明源地覆盖的面积相当于地幔柱供给的大厦（数百平方公里）。这种广阔的，古老的火山地形在南部高地保留了数十亿年，这表明火星地壳二分法的形成，一个地形和地球物理划分之间的严重陨石坑的南部高地和平坦的平原的北方低地，可能早于NWA 7034源地形的定位，也就是说，它形成在第一个~100 Ma的行星形成。
The metamorphic history of martian meteorite NWA 7034 suggests that the martian crustal dichotomy may have formed within 100 million years of planetary formation. Martian meteorite Northwest Africa (NWA) 7034 and its paired stones are the only brecciated regolith samples from Mars with compositions that are representative of the average martian crust. These samples therefore provide a unique opportunity to constrain the processes of metamorphism and alteration in the martian crust, which we have investigated via U-Pu/Xe, 40Ar/39Ar, and U-Th-Sm/He chronometry. U-Pu/Xe ages are comparable to previously reported Sm-Nd and U-Pb ages obtained from NWA 7034 and confirm an ancient (>4.3 billion years) age for the source lithology. After almost 3000 million years (Ma) of quiescence, the source terrain experienced several hundred million years of thermal metamorphism recorded by the K-Ar system that appears to have varied both spatially and temporally. Such protracted metamorphism is consistent with plume-related magmatism and suggests that the source terrain covered an areal extent comparable to plume-fed edifices (hundreds of square kilometers). The retention of such expansive, ancient volcanic terrains in the southern highlands over billions of years suggests that formation of the martian crustal dichotomy, a topographic and geophysical divide between the heavily cratered southern highlands and smoother plains of the northern lowlands, likely predates emplacement of the NWA 7034 source terrain—that is, it formed within the first ~100 Ma of planetary formation.
登录
查看更多内容
影响因子：
5.3
作者：
Bellucci, J. J.;Nemchin, A. A.;Zanda, B.
通讯作者：
Zanda, B.
影响因子：
5.3
作者：
Cartwright, J. A.;Ott, U.;Agee, C. B.
通讯作者：
Agee, C. B.
DOI：
10.1029/jb091ib13p00e99
发表时间：
1986-11-30
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS
影响因子：
--
作者：
BOGARD, DD;HORZ, F;JOHNSON, PH
通讯作者：
JOHNSON, PH
影响因子：
5.3
作者：
Cassata, William S.;Renne, Paul R.;Shuster, David L.
通讯作者：
Shuster, David L.
影响因子：
64.8
作者：
FIELDS, PR;FRIEDMAN, AM;SABINE, WK
通讯作者：
SABINE, WK