Chemistry of the Apollo 11 Highland Component

Abstract

Chemical data (28 major, minor, and trace elements) were obtained by instrumental neutron activation analysis (INAA) for 38 hand‐picked highland fragments (1–20 mg) from coarse fines 10085. The Apollo 11 highland chemical groups are represented by a range of petrographic types. Six major chemical highland groups are identified in the Apollo 11 fragments. These are (1) high‐K KREEP; (2) anorthosite (e.g., 15415, 60015) with 10× chondrite rare‐earth‐elements (REE) abundances, a positive Eu anomaly, anorthosite with 30× chondrite abundances, and a positive Eu anomaly; (3) anorthosite‐norite‐troctolite (ANT) (67075); (4) Low‐K Fra Mauro (LKFM) (77135); (5) anorthositic gabbro (68415) with no Eu anomaly, anorthositic gabbro (65055, 67955) with a positive Eu anomaly, and anorthositic gabbro (68516, 60015) with a negative Eu anomaly; and (6) Apollo 11 ‘dominant highland component,’ 2×–10× chondrite REE abundances with a positive 10×–14× chondrite Eu anomaly. There are three newly‐recognized groups in the Apollo 11 highland suite, based on the REE patterns. These are: (a) ANT with 5× chondrite La, 22× chondrite abundances, and a positive Eu anomaly; (b) 10× chondrite flat pattern with 14× chondrite positive Eu anomaly; and (c) 2–3× chondrite flat pattern with 10× chondrite positive Eu anomaly. The Apollo 11 highland suite is very low in potassium (non‐KREEPy). Overall, the Apollo 11 highland suite is quite similar to the Apollo 16 suite. Most previously recognized highland chemical groups are represented in the Apollo 11 highland component.