1. Jeff Taylor Pristine Highland Rocks1 Rock Names Ferroan anorthosite suite Mg-rich suite –Troctolites –Norites –Gabbro-norites –Others Evolved Lithologies (Alkali suite) –KREEP basalts –Alkali anorthosites and other rocks –“Granites” (felsites) –Ferrobasaltic “rocks”

2. Jeff Taylor Pristine Highland Rocks2 Rock Names Le Maitre et al. (2002)

3. Jeff Taylor Pristine Highland Rocks3 Rock Names Le Maitre et al. (2002)

4. Jeff Taylor Pristine Highland Rocks4 Rock Names Le Maitre et al. (2002)

5. Jeff Taylor Pristine Highland Rocks5 Three Suites of Highland Igneous Rocks Distinctive groups on plots involving Mg# [molar Mg/(Mg+Fe)] vs An in plagioclase (or other variants of that) Ferro-anorthosites: Mg# < 75 (most < 65) Plagioclase is very rich in Ca (high anorthite content) FAN suite Chap 2, New Views of the Moon

6. Jeff Taylor Pristine Highland Rocks6 Three Suites of Highland Igneous Rocks

7. Jeff Taylor Pristine Highland Rocks7 Three Suites of Highland Igneous Rocks

8. Jeff Taylor Pristine Highland Rocks8 Three Suites of Highland Igneous Rocks

9. Jeff Taylor Pristine Highland Rocks9 Three Suites of Highland Igneous Rocks

10. Jeff Taylor Pristine Highland Rocks10 Three Suites of Highland Igneous Rocks

11. Jeff Taylor Pristine Highland Rocks11 Three Suites of Highland Igneous Rocks

12. Jeff Taylor Pristine Highland Rocks12 Ferroan Anorthosite Suite Most > 85 vol% plagioclase –Many 99 vol% –Some only 70-80 vol% Warren (1993)

13. Jeff Taylor Pristine Highland Rocks13 Ferroan Anorthosite Suite Some anorthosites (like 15415) have remnant cumulate texture, but have been granulated (sheared), and then metamorphosed. Shows complex history of highlands crust. Complex history makes it difficult to date the rocks. 15415 0.5 mm

14. Jeff Taylor Pristine Highland Rocks14 Anorthosite 62236: Remnant texture preserved in places 0.5 mm

15. Jeff Taylor Pristine Highland Rocks15 Anorthosite clast 67915,137: Cumulate texture still visible, though rock is shocked. 0.25 mm

16. Jeff Taylor Pristine Highland Rocks16 Anorthosite clast 67915,137: Cumulate texture still visible, though rock is shocked. 0.25 mm

17. Jeff Taylor Pristine Highland Rocks17 Anorthosite 60025: Rock crushed, but there are mafic-rich regions, exsolution in pyroxene, big crystals. 0.5 cm

18. Jeff Taylor Pristine Highland Rocks18 Ferroan Anorthosite Suite Anorthosite suite can be subdivided another way: –Mafic magnesian > 11 vol% mafic silicates Mg# > 65 –Anorthositic, ferroan Mg# < 65 These most abundant –Anorthsitic, sodic Plag has An 94-95 vs An >95 for the others –Mafic ferroan > 8 vol% mafic silicates Mg# < 55 James et al. (1989)

19. Jeff Taylor Pristine Highland Rocks19 Ferroan Anorthosite Suite Trends of minor and trace element concentrations in orthopyroxene, augite, and plagioclase in FAS rocks more complicated than a simple case of crystallization in a single fractionating magma. –No magma ocean? –Or a complicated magma ocean? Concentrations in ppm (except for mg#) Floss et al. (1998) Orthopyroxene

20. Jeff Taylor Pristine Highland Rocks20 Ferroan Anorthosite Suite AugitePlagioclase

21. Jeff Taylor Pristine Highland Rocks21 Plotting Rare Earth Elements Abundances in CI chondrites http://epsc.wustl.edu/admin/resources/chondritic_abundances.html Anders E. and Grevesse N. (1989) Abundances of the elements: Meteoritic and solar. Geochim. et Cosmochim. Acta 53, 197-214.

22. Jeff Taylor Pristine Highland Rocks22 Plotting Rare Earth Elements REE plotted in order of increasing atomic number and decreasing ionic radius Smoothed out by dividing conc by conc in CI chondrites Can be normalized to something else (e.g., suspected parent magma)

23. Jeff Taylor Pristine Highland Rocks23 Ferroan Anorthosite Suite Large positive Eu anomalies on REE plots Normalized concentrations fairly low (1-2 x chondrites)

24. Jeff Taylor Pristine Highland Rocks24 REE in Plagioclase

25. Jeff Taylor Pristine Highland Rocks25 Trace Element Behavior For dilute solutions, like trace elements, we can use D, the distribution coefficient: C S is the concentration of an element in the solid (mineral). C L is the concentration of an element in the liquid (magma). Incompatible elements have D << 1 Compatible elements have D >> 1

26. Jeff Taylor Pristine Highland Rocks26 REE Partition Coefficients OlivinePlagioclaseOrthopyroxene La.0001.042.007 Ce.0001.0302.009 Nd.0001.0236.014 Sm.0006.017.022 Eu.00071.2.015 Gd.0007.0105.037 Dy.003.0089.06 Er.008.0077.10 Yb.019.0065.17 Lu.03.0068.22

27. Jeff Taylor Pristine Highland Rocks27 REE in Parent Magmas

28. Jeff Taylor Pristine Highland Rocks28 Ferroan Anorthosite Suite Plagioclase, especially REE contents, are most consistent with crystallization from single evolving magma. In some subgroups, decoupling of plagioclase from pyroxene compositions –Probably reflect complexities in a huge magma system Caution: subsolidus equilibration can affect trace element concentrations, so data may not reflect igneous environment

29. Jeff Taylor Pristine Highland Rocks29 Mg Suite (a.k.a. Magnesian Suite) Diverse in –Mineral abundances –Mineral compositions –Bulk compositions More mafic than ferroan anorthosite suite Rock types: –Dunite: >90% olivine –Troctolites: half olivine, half plagioclase –Norites: half low-Ca pyroxene, half plagioclase –Gabbro-norites: half (about) plagioclase, low-Ca pyroxene about equal to augite (richer in alkali elements cf norites, troctolites)

30. Jeff Taylor Pristine Highland Rocks30 Mg-rich Suite Mineral compositionsBulk compositions Higher mg#, MgO, and FeO than rocks in the ferroan anorthosite suite.

31. Jeff Taylor Pristine Highland Rocks31 Highland Igneous Rocks Courtesy of Josh Cahill

32. Jeff Taylor Pristine Highland Rocks32 Mg-rich Suite Dunite 72415 0.5 mm

33. Jeff Taylor Pristine Highland Rocks33 Norite 76266 0.5 mm

34. Jeff Taylor Pristine Highland Rocks34 Mg-rich Suite Gabbro-norites –High-Ca pyroxene about equal in abundance as low- Ca pyroxene –Higher ni Ti and Ti/Sm than other Mg-suite rocks –Richer in alkali elements— many are classified as members of the alkalic suite –REE similar to norites and abundance seems to be correlated with Mg# 67915,193

35. Jeff Taylor Pristine Highland Rocks35 Mg-rich Suite Mg-suite rocks have higher REE than ferroan anorthosites. Gabbro-norites have similar REE contents as norites TroctolitesNorites Troctolites Norites

36. Jeff Taylor Pristine Highland Rocks36 Mg-Suite Parent Magmas

37. Jeff Taylor Pristine Highland Rocks37 Mg-Suite Parent Magmas

38. Jeff Taylor Pristine Highland Rocks38 Alkali Suite KREEP basalts –Definition of “KREEP” –Nature of the rocks Alkali suite (anorthosites, norites, gabbro- norites) Granites (felsites) Ferrobasaltic “rocks”

39. Jeff Taylor Pristine Highland Rocks39 Alkali Suite

40. Jeff Taylor Pristine Highland Rocks40 Alkali Suite

41. Jeff Taylor Pristine Highland Rocks41 Alkali Suite

42. Jeff Taylor Pristine Highland Rocks42 KREEP KREEP is a distinctive chemical component in some lunar rocks (both highlands and mare basalts)—it is not a rock type Gets its name from enrichments in incompatible elements, such as K, REE, P, Zr, U, Th Its REE pattern is surprisingly uniform in rocks containing the KREEP signature May be late-stage fractional crystallization product of the magma ocean Chondrite-normalized La/Lu = 2.2 Data from Warren, 1989

43. Jeff Taylor Pristine Highland Rocks43 KREEP basalts High contents of trace elements Typical KREEP rare earth pattern

44. Jeff Taylor Pristine Highland Rocks44 KREEP basalts Classic volcanic texture 15386 0.5 mm

45. Jeff Taylor Pristine Highland Rocks45 KREEP basalts 0.5 mm Texture similar to terrestrial basalts (specifically similar to pahoehoe). 15386Hawaiian pahoehoe

46. Jeff Taylor Pristine Highland Rocks46 KREEP basalts Composed mostly of plagioclase and pigeonite Pyroxenes typical of basaltic compositions, trending from pigeonite to subcalcic augite to augite

47. Jeff Taylor Pristine Highland Rocks47 KREEP Basalts and Differentiates

48. Jeff Taylor Pristine Highland Rocks48 KREEP basalts A-15 KREEP basalts appear to be an igneous system—they plot along a cotectic A-15 KREEP basalts show an extensive low-P fractional crystallization sequence, ending with a rock called the quartz monzodiorite A-17 KREEP basalts not related to A-15, but only limited sampling

49. Jeff Taylor Pristine Highland Rocks49 KREEP basalts: Quartz Monzodiorite Found at Apollo 14 and 15 Evolved composition: –High REE –High Fe/Mg Fractional crystallization product of KREEP basalt Suggests alkalic rocks can be formed by fractionation of a KREEP basalt magma 1 mm

50. Jeff Taylor Pristine Highland Rocks50 Alkali Suite > 90% plagioclase (more or less) Plagioclase is very sodic, by lunar standards High REE and have typical KREEP patterns Rich in phosphate minerals (which is where REE reside) Gabbro-norites and norites Really are plagioclase- rich mafic cumulates Anorthosites and granites only from Apollo 12, 14, and 15, but mafic ones from A-16 and 17, too (western and eastern near side) Alkali Anorthosites Mafic Alkalic Rocks

51. Jeff Taylor Pristine Highland Rocks51

52. Jeff Taylor Pristine Highland Rocks52 “Granites” 0.5 mm Qtz Kspar

53. Jeff Taylor Pristine Highland Rocks53 Granites Not really coarse-grained rocks like terrestrial granites, and they do not compose huge intrusions—should be called “felsites.” –Biggest is a 1.9-gram fragment in a breccia! –But they do have some coarse, graphic intergrowths consisting of quartz and albite REE pattern not exactly KREEP-like 1 mm

54. Jeff Taylor Pristine Highland Rocks54 Ferrobasaltic Rocks Found as fine-grained melts or even glasses Rich in FeO (> 25 wt%) Very rich in REE Formation likely to have involved silicate liquid immiscibility, which may have produced felsites at the same time

55. Jeff Taylor Ferrobasalts – Felsite Pair Pristine Highland Rocks55

56. Jeff Taylor Pristine Highland Rocks56 Parent Magmas (from Plagioclase)

57. Jeff Taylor Pristine Highland Rocks57 Terrestrial Continents Continental crust/primitive mantle =  30 Upper crust/primitive mantle =  55 Granite/primitive mantle =  100 Moon evolved rocks/lunar primitive mantle =  1000