The NWA 11004 ordinary chondrite (OC) can provide insights into the complex petrogenetic processes of the early solar system. Although originally classified as an L7 chondrite, it is reclassified as LL based on kamacite Ni (4.9 ± 0.3 wt.%) and Co (3.6 ± 0.5 wt.%) and bulk O‐isotopic composition (δ¹⁷O = 3.76‰; δ¹⁸O = 5.39‰). NWA 11004 is characterized by (1) the occurrence of 3‐ to 5‐mm‐sized poikilitic pyroxene, (2) scattered low‐Ca pyroxene data in a TiO₂ versus Al₂O₃ diagram, (3) relatively magnesian olivine and low‐Ca pyroxene (Fa_25.4, Fs_21.3), (4) low abundances of high‐Ca pyroxene, plagioclase, troilite and Ca‐phosphate, and (5) low rare earth element contents in low‐Ca pyroxene. The geochemical features of olivine and low‐Ca pyroxene in NWA 11004 differ from literature data for grains that crystallized from a melt in an OC impact melt breccia. We suggest that in NWA 11004, a plagioclase‐phosphate high‐Ca pyroxene‐troilite melt migrated away during partial melting. Some high‐Ca pyroxene grains crystallized from the residual melt, as indicated by a positive linear trend in a TiO₂ versus Al₂O₃ diagram. Whereas poikilitic low‐Ca pyroxene in NWA 11004 exhibits undulose‐to‐weak mosaic extinction, the olivine chadacrysts exhibit sharp optical extinction; this implies that NWA 11004 experienced a late‐stage shock event (S4) followed by annealing. The Ca‐phosphate ²⁰⁷Pb/²⁰⁶Pb age of 4546 ± 34 Ma most likely dates this late‐stage shock event. We suggest that the presence of type 7 OC in the early solar system may be attributable to impacts on warm chondritic asteroids that were initially heated by the decay of ²⁶Al.

中文翻译：

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对软骨母体的早期影响事件：NWA 11004的见解，重新分类为LL7角砾岩

NWA 11004普通球粒陨石（OC）可以洞悉早期太阳系的复杂成岩过程。虽然最初分类为L7陨石，它是基于纹石的Ni（4.9±0.3重量％）和Co（3.6±0.5重量％）和主体O形同位素组成（δ重新分类为LL ¹⁷ O = 3.76‰;δ ¹⁸ O = 5.39‰）。NWA 11004的特征在于（1）发生3至5毫米大小的多方辉石​​，（2）TiO ₂与Al ₂ O ₃图表中的分散的低钙辉石数据，（3）镁质橄榄石和低镁橄榄石Ca Ca ox（Fa _25.4，Fs _21.3），（4）高钙辉石，斜长石，三叶草和磷酸钙的含量低，（5）低钙辉石中的稀土元素含量低。NWA 11004中的橄榄石和低钙辉石的地球化学特征与OC冲击熔岩角砾岩中从熔体结晶的晶粒的文献数据不同。我们建议在NWA 11004中，斜长石磷酸盐-高钙辉石-三菱沸石熔体在部分熔融过程中迁移。TiO ₂与Al ₂ O ₃的正线性趋势表明，一些高钙的辉石晶粒从残留的熔体中结晶出来。图。NWA 11004中的滑石质低钙辉石表现出从无到弱的镶嵌灭绝，而橄榄石cha石则表现出强烈的光学灭绝。这意味着NWA 11004经历了后期冲击事件（S4），然后进行退火。磷酸钙的²⁰⁷ Pb / ²⁰⁶ Pb年龄为4546±34 Ma，最有可能是这一晚期电击事件的发生日期。我们建议早期太阳系中7型OC的存在可能是由于对最初由²⁶ Al的衰变加热的温暖的软骨小行星的影响。