一块仅3个被批准为L3熔融角砾岩的陨石

2017-04-24

Meteorite NWA 12547, Classified as L3-Melt Breccia

陨石NWA 12547，分类为L3熔融角砾岩

NWA 12547

Chondrite

L3-Melt Breccia

Found Sahara, 2018

Specimen is a 1.23g slice

The recommended classification L3-melt breccia means:

"An ordinary chondrite from the L group that is petrologic type 3 and is a breccia with melted material forming the matrix."

The highlighted words are defined as follows:

ordinary chondrite: A major class of chondrites, distinguished by sub-solar Mg/Si and refractory/Si ratios, oxygen isotope compositions that plot above the terrestrial fractionation line, and a large volume percentage of chondrules, with only 10-15 vol% fine-grained matrix.

L group: The low-iron (L) chemical group of ordinary chondrites, distinguished by their relatively low siderophile element content, moderate sized chondrules (~0.7 mm), and oxygen isotope compositions that intermediate between H and LL group ordinary chondrites.

type 3: Designates chondrites that are characterized by abundant chondrules, low degrees of aqueous alteration, and unequilibrated mineral assemblages. Many of the low-Ca pyroxene grains are monoclinic and exhibit polysynthetic twinning. The type 3 chondrites may be divided into subtypes ranging from 3.00 (least metamorphosed) to 3.9 (nearly metamorphosed to type 4 levels). If primary igneous glass occurs in the chondrules, it belongs to type 3.

This is 1 of 3 approved meteorites classified as L3-melt breccia

*Chondrite were formed by the accretion of particles of dust and grit present in the primitive Solar System which gave rise to asteroids over 4.55 billion years ago. These

asteroid parent bodies of chondrites are (or were) small to medium-sized asteroids that were never part of any body large enough to undergo melting and planetary differentiation. Dating using 206Pb/204Pb gives an estimated age of 4,566.6 ± 1.0 Ma, matching ages for other chronometers. Another indication of their age is the fact that the abundance of non-volatileelements in chondrites is similar to that found in the atmosphere of the Sun and other stars in our galaxy.

*Chondrules (clearly visible as round mineral formation on the meteorite) represent one of the oldest solid materials within the Solar System, and are unique to the chondrites meteorites. They are believed to have formed by a rapid (flash) heating (within minutes or less) and melting of solid dust aggregates of approximately Solar composition under temperatures of about 1000 K (the solar nebula or a protoplanetary environment are possible places of formation). Isotope studies of chondrules indicate a nearby supernova explosion added fresh material to what became the Solar System.

NWA 12547

球粒陨石

L3—熔融角砾岩

发现了撒哈拉沙漠，2018年

标本是一个1.23g个体

建议的分类L3-melt角砾岩意味着：

“来自L组的普通球粒陨石是岩石类型3，是角砾岩，熔化的物质形成基质。”

突出显示的单词定义如下：

普通球粒陨石：一种主要的球粒陨石，其特征是亚太阳离子Mg / Si和耐火材料/ Si比率，在地面分馏线以上绘制的氧同位素组成，以及大量百分比的陨石球粒，仅有10-15 vol％的细粒 - 矩阵。

L组：普通球粒陨石的低铁（L）化学组，其特征在于它们相对低的嗜铁元素含量，中等大小的陨石球粒（~0.7mm），以及介于H和LL组普通球粒陨石之间的氧同位素组成。

类型3：指定具有丰富的陨石球粒，低水平变化和未平衡的矿物组合的球粒陨石。许多低Ca辉石颗粒是单斜晶系并且表现出多聚合物孪晶。 3型球粒陨石可分为从3.00（最小变形）到3.9（几乎变形到4型水平）的亚型。如果初级火成玻璃出现在陨石球间，则属于3型。

这是1个标准的meteorites L3分类的熔融角砾岩

*球粒陨石是由原始太阳系中存在的尘埃和沙砾颗粒的形成而形成的，这些颗粒在45.5亿年前产生了小行星。这些小球团的小行星母体是（或者是）小到中等大小的小行星，它们从不是任何大到足以进行融化和行星分化的物体的一部分。使用206Pb / 204Pb进行约会，估计年龄为4,566.6±1.0 Ma，与其他计时器的年龄相匹配。它们年龄的另一个迹象是，球粒陨石中非挥发性元素的丰度与太阳大气层和银河系中其他恒星中的非挥发性元素相似。

* Chondrules（在陨石上清晰可见的圆形矿物形成）代表了太阳系中最古老的固体材料之一，并且是球粒陨石的独特之处。它们被认为是通过快速（闪蒸）加热（在几分钟或更短时间内）形成的，并且在约1000K的温度下（太阳星云或原行

星环境是可能的形成位置）熔化大约太阳能组合物的固体粉尘聚集体。陨石球粒的同位素研究表明附近的超新星爆炸为太阳系增添了新的材料。

西北非12547

基本情况名称：西北非12547

这是一个官方的陨石名称。

缩写：NWA 12547

观察到的坠落：否

发现年份：2019年

国家：摩洛哥

质量：747克

分类

历史记录：