Evidence for successive episodes of condensation at high temperature in a part of the solar nebula
Evidence for successive episodes of condensation at high temperature in a part of the solar nebula
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太阳星云的一部分在高温下连续发生凝结的证据
DOI：
10.1016/0012-821x(86)90155-x
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发表时间：
1986
影响因子：
5.3
通讯作者：
D. Wark
中科院分区：
文献类型：
--
作者：
D. Wark
阿连德陨石中一个厘米级的Casingle键富铝包体CAI 3643，保存了它在高温下凝结生长的多个阶段的记录。它由三个不同的同心层--地核、地幔和地壳组成。的开放纹理的核心是由黑云母板条，填隙黄长石和空隙，氧化铝颗粒，和OsIr金属熔核的内芯是互补的组合物中的外芯的RuPt丰富的熔核。地核是由同一个气藏中两次凝结的快速聚集晶体形成的。熔核中的Mo和W耗尽表明相对氧化性气体的冷凝，其H/2 OH 2比太阳能气体高60倍。致密的粗黄长石地幔中含有钙钛矿型包裹体和稀有的NiFe金属和硫化物颗粒。致密、细粒的地壳由黄长石、黑云母、尖晶石、钙钛矿和类似于地幔中的不透明物组成。地幔和地壳都没有被熔化，它们都是通过固体直接凝结在CAI表面而生长的。形成的CAI经历了黄长石的变质重结晶，以及生成钙铝榴石、铁铝尖晶石和铁铝尖晶石的挥发性蚀变。钙钛矿和大量样品的微量元素分析表明，地幔和地壳中的耐火元素（即第二组）和补充超耐火的核心。尽管在结构和成分上存在差异，但地核、地幔和地壳在其模态矿物学成分上显示出连续性，其极端的Al 2 O3富集（53-69% cf. 25-45%的其他CAI）和它们的微量元素互补性。这意味着3643的所有层都是在有限的时间和空间间隔内由相同的冷却气体储层形成的，这与星云CV球粒陨石形成区域的局部瞬时加热事件的起源一致。
A centimeter-sized Casingle bondAl-rich inclusion, CAI 3643, in the Allende meteorite has preserved a record of its multiple stages of growth by condensation at high temperature. It consists of three distinct, concentric layers—core, mantle and crust. The open-textured core is composed of hibonite laths, interstitial melilite and voids, grains of alumina, and OsIr metal nuggets in the inner core that are complementary in composition to RuPt-rich nuggets in the outer core. The core formed out of rapidly-aggregated crystals from two episodes of condensation in the same gaseous reservoir. Mo and W depletions in the nuggets indicate condensation from a relatively oxidizing gas, with 60 times higherH/2OH2than solar gas. The compact mantle of coarse melilite contains perovskite inclusions and rare NiFe metal and sulfide grains. The compact, fine-grained crust consists of melilite, hibonite, spinel, perovskite, and opaques similar to those in the mantle. Neither mantle nor crust has been molten; each grew by condensation of solids directly onto the surface of the CAI. The formed CAI experienced some metamorphic recrystallization of melilite, and volatile alteration producing grossular, feldspathoids and hercynite. Trace element analyses of perovskites and a bulk sample show the mantle and crust to be depleted in refractory elements (i.e. Group II) and complementary to the ultra-refractory core. Despite differences in texture and composition, the core, mantle and crust display a continuity in their modal mineralogical compositions, their extreme Al2O3enrichments (53–69% cf. 25–45% for other CAI's) and their trace element complementarity. This implies that all the layers of 3643 formed from the same cooling gaseous reservoir within a limited interval of time and space, consistent with an origin in a local, transient heating event in the CV chondrite formation region of the nebula.