Abstract
Research subject . The article presents the results of a study of a new meteorite Northwest Africa 11781. Material and methods. The material for the study was a fragment of a meteorite weighing 15.56 g, from which 4 transparent polished sections with a total area of 10.5 cm 2 were produced. The mineralogy and structural features of the meteorite were studied using a scanning electron microscope JSM-6390LV by JEOL, an electron probe microanalyzer Cameca SX-100 and a quadrupole mass spectrometer with inductively coupled plasma ELAN 9000. All analyses were performed in core facilities “Geoanalytic” IGG UB RAS. Results. The meteorite is CM2 carbonaceous chondrite comprising ≈ 20-30% of chon-drules and 60-70% of a fine-grained matrix. Refractory inclusions (CAI, AOAs, forsterite rich objects) occupy no more than 3-5%. The average chondrule size is 0.3 mm. Porphyritic olivine (PO) and olivine-pyroxene (POP) chondrules predominate. The meteorite matrix consists of layered silicates and iron hydroxides. CAIs are small in size (0.05-0.3 mm). The main minerals of CAIs are spinel, Ca-pyroxene, hibonite and perovskite. Olivone in AOAs mainly contains spinel-diopside inclusions. The forsterite-rich object presents a low-Fe forsterite with a low-Fe enstatite margin. The meteorite also features an unusually large (1 mm) forsterite-rich object. This object has a transitional position from refractory forsterite to magnesian chondrules. Unusual isolate crystals of high-Fe (FeO 15.35-38.89 wt %) olivine were identified in the meteorite matrix. The mechanism of their formation remains controversial. Conclusion. It is established that the discovered fragment is a carbonaceous chondrite, therefore being a meteorite that has not been studied before. The meteorite has been recorded as a new carbonaceous chondrite called Northwest Africa 11781 (NWA 11781). The meteorite shows no signs of a shock impact and demonstrates a high grade of terrestrial weathering.
Highlights
The article presents the results of a study of a new meteorite Northwest Africa 11781
The material for the study was a fragment of a meteorite weighing 15.56 g, from which 4 transparent polished sections with a total area of 10.5 cm2 were produced
The meteorite is CM2 carbonaceous chondrite comprising ≈ 20–30% of chondrules and 60–70% of a fine-grained matrix
Summary
Исходным материалом для исследования послужил фрагмент метеорита массой 15.56 г, покрытый со всех сторон корой плавления черного цвета (рис. 1). Исходным материалом для исследования послужил фрагмент метеорита массой 15.56 г, покрытый со всех сторон корой плавления черного цвета Было изготовлено 4 прозрачнополированных шлифа общей площадью 10.5 см. Изучение минералогии и структурных особенностей метеорита NWA 11781 проводилось на сканирующем электронном микроскопе JSM6390LV фирмы JEOL с энергодисперсионной приставкой INCA Energy 450 X-Max 80 фирмы Oxford Instruments Состав минералов исследован на электронно-зондовом микроанализаторе Cameca SX-100 Для изучения содержания редких и рассеянных элементов небольшой фрагмент метеорита был проанализирован на квадрупольном массспектрометре с индуктивно-связанной плазмой ELAN 9000 фирмы PerkinElmer. Все анализы были выполнены в ЦКП “Геоаналитик” в ИГГ УрО РАН. Микроэлементный состав метеорита NWA 11781 приведен в табл. 1, спайдер-диаграммы распределения редкоземельных, а также халькофильных и сидерофильных элементов показаны на рис.
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