Radiometric dating of young MORB using the 40Ar‐39Ar incremental heating method
Radiometric dating of young MORB using the 40Ar‐39Ar incremental heating method
复制标题
使用 40Ar-39Ar 增量加热法对年轻 MORB 进行辐射测年
DOI：
10.1029/94gl01375
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发表时间：
1994
影响因子：
5.2
通讯作者：
L. Hogan
中科院分区：
文献类型：
--
作者：
R. Duncan;L. Hogan
用K-Ar法测定年轻（<1 Ma）的海底新鲜玄武岩的可靠结晶年龄受到若干因素的影响。在这些时间尺度上，在这种低K岩石中形成的少量放射性成因40 Ar很难从主要的大气40 Ar中分辨出来。另一个问题是，地幔衍生的40 Ar可能不会完全脱气时，岩浆在海底流体静压淬火。我们已经制定了一个成功的战略，部分分离大气放射性40 Ar在40 Ar-39 Ar增量加热实验洋中脊玄武岩，从东太平洋隆起附近的克利珀顿断裂带。将样品预热到400°C会去除表面的大气40 Ar，而随后在600°-1000 ° C加热会产生有利比例的放射性40 Ar。使用“零年龄”玻璃和全晶质样品的实验表明，幔源40 Ar仅保留在快速冷却的枕状玄武岩的最外几厘米。
Determination of reliable crystallization ages by K-Ar methods for young (<1 Ma), fresh basalts from the seafloor has been frustrated by several effects. The small amounts of radiogenic 40Ar developed over these timescales in such low-K rocks are difficult to resolve from predominantly atmospheric 40Ar. An additional concern is that mantle-derived 40Ar may not be totally outgassed when magmas quench at seafloor hydrostatic pressures. We have developed a successful strategy for partially separating atmospheric from radiogenic 40Ar in 40Ar-39Ar incremental heating experiments on mid-ocean ridge basalts, from the East Pacific Rise near the Clipperton Fracture Zone. Pre-heating samples to 400°C removes surficial atmospheric 40Ar, while subsequent heating at 600°–1000°C produces favorable proportions of radiogenic 40Ar. Experiments using “zero-age” glassy and holocrystalline samples show that mantle-derived 40Ar is retained only in the outermost few cm of rapidly cooled pillow basalts.