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Jul 1, 2015 - Roger Putnam1, Allen F. Glazner1, Drew S. Coleman1, Andrew R.C. Kylander-Clark2, Tamlin Pavelsky1, and Miquela I. Abbot1,3.
Research Paper

GEOSPHERE

Plutonism in three dimensions: Field and geochemical relations on the southeast face of El Capitan, Yosemite National Park, California

GEOSPHERE; v. 11, no. 4

Roger Putnam1, Allen F. Glazner 1, Drew S. Coleman1, Andrew R.C. Kylander-Clark2, Tamlin Pavelsky1, and Miquela I. Abbot 1,3 doi:​10​.1130​/GES01133​.1

1 2

20 figures; 6 supplemental files

3

Department of Geological Sciences, University of North Carolina, Chapel Hill, North Carolina 27599-3315, USA Department of Earth Science, University of California, Santa Barbara, California, 93106-9630, USA Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, 60637, USA

CORRESPONDENCE: [email protected] CITATION: Putnam, R., Glazner, A.F., Coleman, D.S., Kylander-Clark, A.R.C., Pavelsky, T., and Abbot, M.I., 2015, Plutonism in three dimensions: Field and geochemical relations on the southeast face of El Capitan, Yosemite National Park, California: Geosphere, v.  11, no.  4, p.  1133–1157, doi:​​10​​.1130​​/GES01133​.1​. Received 5 October 2014 Revision received 14 May 2015 Accepted 11 June 2015 Published online 1 July 2015

ABSTRACT Detailed geologic mapping on the ~1-km-tall, vertical southeast face of El Capitan was completed to determine the chronology and geometry of emplacement. Field relations reveal a complex intrusive history at the boundary between two intrusive suites involving interaction between several granitic units. No resolvable faulting or other postemplacement deformation was observed. New U-Pb zircon geochronologic data (laser ablation and isotope dilution) demonstrate assembly of the El Capitan Granite and diorites of the Rockslides and North America between ca. 106 and 103 Ma. New ages for the Taft (106.6 ± 0.7 Ma), Leaning Tower (104.1 ± 0.10 Ma), and Bridalveil (103.4 ± 0.4 Ma) plutons reveal that they intruded over the same interval as the other plutonic rocks exposed on the face of El Capitan, although field relations and geochronology suggest a distinct order of emplacement. Two sets of aplite dikes are also exposed. Their whole-rock compositions suggest segregation at depths of 5–6 km and derivation from the intrusive suites of Yosemite Valley or Buena Vista Crest. Chemical analysis of samples collected along ~1-km-tall vertical transects through the El Capitan and Taft Granites reveals no systematic variations in major or trace elements. Analysis of 78 photographs within the El Capitan Granite also shows no systematic variations in texture or mineralogy with elevation. Lack of resolvable vertical variations in both field and petrologic observations is consistent with incremental assembly, and is hard to reconcile with models that envision magma chambers as large fractionating bodies.

INTRODUCTION

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Plutonic rocks are fundamental building blocks of Earth’s crust, yet much about processes associated with their emplacement and evolution remains poorly understood. Plutons were long viewed as the remains of massive, mobile, largely liquid magma bodies that rose into the crust (Daly, 1933; Buddington, 1959; Bateman, 1992) and were emplaced over time scales on the order of 105 years (e.g., Harrison and Clarke, 1979; Spera, 1980). Recent geochronologic studies, however, show that many plutons were likely assembled over time

scales from 105 to 106 Ma, in batches that are significantly smaller than the full pluton volume (Coleman et al., 2004; Glazner et al., 2004; Matzel et al., 2006; Bolhar et al., 2010; Davis et al., 2012; Leuthold et al., 2012; Schoene et al., 2012; Frazer et al., 2014). These studies are difficult to reconcile with the view that plutons are frozen remnants of large (~103 km3), long-lived (~106–107 m.y.) melt-interconnected reservoirs (e.g., Paterson and Vernon, 1995; Hildreth and Wilson, 2004; Miura and Wada, 2007; Walker et al., 2007; Memeti et al., 2010). Detailed mapping, coupled with geochronologic and geochemical studies of well-exposed plutonic systems, can help to evaluate these models of magma emplacement. In situ crystal-liquid fractionation of a single intrusion is commonly invoked to explain formation of both lateral and vertical zoning in plutons (e.g., Bateman and Chappell, 1979; Atherton, 1981; Tindle and Pearce, 1981; Sawka et al., 1990; Verplanck et al., 1999; Economos, et al., 2009), and vertical profiles of ignimbrites frequently display compositional patterns interpreted to reflect vertical zonation in magma chambers (Bacon and Druitt, 1988; Hildreth and Wilson, 2007). If a pluton crystallized from a largely liquid body at some point, such fractionation should produce both vertical and horizontal zonation in mineral abundances and whole-rock geochemistry, as early crystallizing minerals form and residual melt segregates from them (e.g., Ragland and Butler, 1972; Baker and McBirney, 1985). Several studies (e.g., Sawka et al., 1990; Bachl et al., 2001; Hirt, 2007) have also reported vertical variations in crystal size and modal abundance that were inferred to result from vertical segregation of crystals and liquid within large magma bodies. Vertical variations in incompati­ ble elements produced by this process could also redistribute heat-producing elements (Sawka and Chappell, 1988). By contrast, in an incrementally emplaced pluton, compositional variability cannot have been produced wholly by crystal-liquid separation at the level of observation (Glazner et al., 2004). The overall compositional zoning of many intrusive bodies is thus inferred to result from other processes, such as changes in the composition of the magma supplied from a deeper source (Clemens et al., 2010; Tappa et al., 2011; Coleman et al., 2012), superimposed with local variability produced by crystal-liquid separation. Yosemite Valley, California (Fig. 1), provides opportunities to generate true vertical mapping and geochronologic and geochemical transects through

© 2015 Geological Society of America

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Figure 1. Yosemite Valley looking east from Discovery View. The 900-m-tall granite cliff of El Capitan dominates the left side of the photograph. The shadowed valley floor is at 1200 m elevation; from center to right, the snow-covered north face of Cloud’s Rest (3028 m), Half Dome (2690 m), and Sentinel Rock (2128 m) comprise tall, unbroken granodiorite cliffs and slopes.

largely undeformed plutons, and thus, to test these contrasting views of pluton genesis. Studies of spatial zoning in granitic pluton geochemistry and mineral composition are generally based on observation of outcrop surfaces that have little relief in the vertical dimension compared to the horizontal (e.g., Tindle and Pearce, 1981), although relief of over 2 km can be produced by deep river incision (Cornejo and Mahood, 1997). Undeformed plutons with vertical cliff exposure comparable to or greater than the face of El Capitan are rare and remote (Michel et al., 2008; Searle and Parrish, 2010). Direct observation of significant vertical pluton extents is thus generally limited to plutons exhumed by tilting (e.g., Flood and Shaw, 1979; John, 1988; Seager and McCurry, 1988; Rosenberg et al., 1995; Bachl et al., 2001). Although these examples may ­offer much deeper exposure than those found in single cliffs, such studies are subject to uncertainties in structural reconstruction and interpretation, and the defor­ma­tion that produced the exposure commonly obscures original features in the tilted rocks. Sawka et al. (1990) examined vertical variability in relatively undeformed Jurassic plutons exhumed by normal faulting along the eastern margin of the Sierra Nevada in California. They interpreted variations in major- and traceele­ment data with elevation as being consistent with those predicted by crystal-liquid fractionation models. Although elevation in this area reaches 4205 m with 900 m of topographic relief, the horizontal distance over which this elevation is gained is ~1400 m, resulting in an average slope of 32°. Thus, this ambitious transect is still a relatively low-angle oblique cut through the plutonic system, where differences in elevation are not truly vertical differences in the original system.

GEOSPHERE  |  Volume 11  |  Number 4

In Yosemite Valley, Quaternary glaciation, river erosion, and ongoing rockfall have produced a steep-sided valley with over 1 km of local relief (Fig. 1). The vertical northwest cliff face of Half Dome is 680 m tall, and continuous exposure from the top of Half Dome to Tenaya Creek covers 1340 vertical meters at an average angle of 51°. This entire section is sculpted in one pluton, the Half Dome Granodiorite (Calkins, 1985). El Capitan (Figs. 1 and 2) exposes a 1-km vertical section of plutonic rocks (Calkins, 1985; Peck, 2002) in a massive cliff that is locally overhanging but is typically steeper than 75°. The southeast face of El Capitan has continuous and steep exposure, fully visible from the valley floor, which is crossed by over 70 named climbing routes and is thus more accessible for observation, mapping, and sampling than other km-tall cross sections of granitic systems around the world. Its south-facing aspect provides rock that is largely unobscured by water staining and lichen growth that covers parts of nearby north-facing cliffs such as Half Dome and Glacier Point. Prior work (Calkins, 1930; Reid et al., 1983; Bateman, 1992; Ratajeski et al., 2001) revealed that the southeast face of El Capitan exposes the intersection of two major intrusive suites and two mafic dike swarms. However, understanding contact relationships among these units and their emplacement chronology was hampered by the extreme vertical nature of the study area. In intervening years, new remote sensing tools were devised, the precision of U-Pb geochronology was significantly improved, and rock climbing techniques were refined, making El Capitan a much more accessible exposure on which to study interactions between intrusive units and to test hypotheses regarding the mechanisms and time scales of pluton emplacement in a near-vertical transect. In this article, we present the field relations revealed by decimeter-scale mapping of the southeast face of El Capitan (Putnam et al., 2014), supplemented by new geochemical analyses and U-Pb dating of zircon. These data reveal 3 Ma assembly of the plutonic system and show no evidence for gravity-driven separation of crystals and liquid over the 1 km vertical extent of the cliff. In this contribution, we use climbing route designations (italicized) as landmarks in describing the geology, along with both official and unofficial (e.g., North America; The Alcove) local place names (Fig. 3; Putnam and Sloan, 2014).

GEOLOGIC BACKGROUND El Capitan (Fig. 1) is in the west-central portion of the Sierra Nevada batho­ lith, near the west end of Yosemite Valley (Fig. 2). It was carved in rocks of the intrusive suite of Yosemite Valley (ISYV; Reid et al., 1983; Bateman, 1992; Ratajeski et al., 2001), which is intruded on the east by the massive Tuolumne Intrusive Suite (TIS; Bateman, 1992). Most mapping and sampling of El Capitan has focused on outcrops along the base and on the summit dome and on optical reconnaissance (Calkins, 1930; Bateman 1992; Peck, 2002). Mafic dike swarms cropping out on the face were used to study magma mixing processes by Reid et al. (1983), Ratajeski et al. (2001), and Nelson et al. (2013). A detailed

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119°35′ W

North Dome EC 26 ECS7 ECS726

37°44′ N

The Cookie Slide

YOS-104 YO YOS-104 04 4

El Capitan

CS72 CS CS720 S 0

41

37°42′ N

EC 1 ECS0 ECS01

YOS-23C

Lower Cathedral Rock

LC-01, LC-02

Middle Cathedral Rock

Glacier Point

Taft Point

140

Figure 2. Simplified geology of the Yosemite Valley area, California (CA), modified from Calkins (1985) and Peck (2002). Diorite, gabbro, and all other mafic units are colored green, independent of age or intrusive suite association. All intrusive rocks in the map area were intruded between ca. 115 and 90 Ma (Bateman, 1992), becoming younger from west to east. Some of the map units were intruded contemporaneously. The locations of the geochronology samples are shown (except for RF-01, which was taken near the town of El Portal, ~6 km west of the edge of this map).

Geochronology Sample

map of the summit was made by Ratajeski et al. (2001; Fig. 4), and a portion of the southeast face was mapped in order to study the genesis of a prehistoric rock avalanche (Stock and Uhrhammer, 2010). Geomorphologic and geochronologic data indicate that the Sierra N ­ evada batholith has been tilted westward only a few degrees since the Late Cretaceous (Huber, 1981; House et al., 2001). There are no data suggesting significant postintrusive deformation of the region; so we assume that the near-vertical face of El Capitan represents a vertical transect through the magmatic system.

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The Intrusive Suite of Yosemite Valley Numerous units of the ISYV are exposed on the summit and face of El Capi­ tan. This suite is interpreted to have been emplaced in a continental-arc environment from 105 to 95 Ma (Stern et al., 1981; Bateman, 1992). To the west, the ISYV intrudes Paleozoic metasedimentary rocks and granodioritic units of the 124–105 Ma Fine Gold Intrusive Suite (Lackey et al., 2012). To the east, the ISYV is intruded by the Late Cretaceous TIS (Bateman, 1992), which was emplaced from 95 to 85 Ma (Fig. 2; Coleman et al., 2004; Memeti et al., 2010).

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Salathé Wall

Muir Wall

The Nose

New Dawn Mescalito

Dawn Wall

North America Wall

Figure 7a

Tangerine Trip The Shield

The Great Roof

Zodiac The Prophet

Horsetail Falls

The Devil’s Brow

North America Wall

El Capitan Tower

The Heart

East Buttress

Gray Circle

Figure 8 Figure 8

El Capitan Tree Figure 9b

New Dawn

The N ose

Figure 5

Freeb last

The Alcove

The Footstool

The Black Tower

Figure 9a The Brain

Figure 7c

Figure 7d

Figure 3. Notable locations and climbing routes on the southeast face of El Capitan. The names of each climbing route are listed at the top of the route. General locations are shaded orange. The Nose travels along the curving arête separating the sunlit and shaded parts of the cliff. The North America Wall is the concave section of wall to the right of the Nose, marked by mafic dikes in the shape of North America. The exposure visible in this image is the area of Figure 6. Location names and route paths taken from Putnam and Sloan (2014). The scale bar is an approximate horizontal scale; absolute scale varies because the image is a flattened representation of a three-dimensional surface. The view angle is to the north. Photograph courtesy of www​.xRez​.com.

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Research Paper 267000

269000

268000

2300

Kt

4178000

Kd Kt

Kec

Kd

1800

Summit 2308m Kec

Kd

Kd

Kd

Figure 4. Geologic map of the El Capitan summit area modified from Calkins (1985) and Ratajeski et al. (2001). Shaded gray polygon is the southeast face of El Capitan and the area of Figures 3 and 6. Most contacts on this map are sharp to locally gradational. There is over 1000 m of relief between the summit and base of El Capi­ tan and over 900 m of relief in the map area. Dashed line is hiker’s trail to summit, and solid black lines are roads. The contour interval is 100 m, and the UTM datum is NAD83, zone 11S.

Kt

Kgb

Kd Kd Kt

4179000

Kt

Kt

0

130

0

0.25

El Capitan Picnic Area

Base 1255m

Qat

0.5

1

El Capitan Meadow Qat

Alluvium and talus

Kd

Diorite, gabbros, & other mafic rocks

N Kgb Tonalite of the Gray Bands Kt

Kec

k

El Capitan Granite

Taft Granite

Petrographic characteristics of the ISYV were described by Calkins (1930), Pabst (1938), Smith (1967), Reid et al. (1983), Bateman et al. (1984), and Ratajeski et al. (2001), and chemical analyses of various units were presented by Reid et al. (1983), Bateman et al. (1984), Ratajeski et al. (2001), and Nelson et al. (2013).

Granites The El Capitan Granite is the dominant unit exposed on the southeast face of El Capitan and was the first unit to be emplaced (Ratajeski et al., 2001). The main body of the pluton is 30 km long and 5 km wide and is a principal mem-

GEOSPHERE  |  Volume 11  |  Number 4

iver

Merced R

El Capitan Bridge

Km

ber of the ISYV (Huber et al., 1989; Bateman, 1992). It is slightly porphyritic with 1–2 cm K-feldspar phenocrysts and biotite as the principal mafic mineral. Existing U-Pb zircon isotope dilution–thermal ionization mass spectrometry (ID-TIMS) geochronologic data for the El Capitan Granite in the type locality are discordant but suggest an age of 105–102 Ma (Ratajeski et al., 2001). The Taft Granite, a medium-grained, equigranular biotite granite, intrudes and is more leucocratic than the El Capitan Granite. The El Capitan and Taft Granites overlap on all major- and trace-element trends, although the Taft is generally more felsic (Bateman, 1992). This granite has proven difficult to date: Stern et al. (1981) obtained a discordant U-Pb zircon ID-TIMS age of 95 Ma, but Ratajeski et al. (2001) found that Taft zircons, like those of the El Capitan, plot near concordia at 105–102 Ma.

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Research Paper Mafic Units The El Capitan and Taft Granites are both cut by a series of compositionally diverse, biotite-rich, hornblende-poor, moderately dipping dikes and pods of dioritic to granodioritic rock previously referred to as pre–North America dikes (Ratajeski et al., 2001) and herein called dikes of the Oceans after their abundance in the outcrops east and west of the North America feature (Fig. 3). These dikes contain partially reacted xenoliths of other plutonic rocks up to 15 m across (Reid et al., 1983; Ratajeski et al., 2001). A steeply south-dipping tonalitic unit crops out in the center of the Nose. This unit was mapped as diorite separating the El Capitan and Taft Granites by Calkins (1985) and Peck (2002), and it was mapped by Ratajeski et al. (2001) as a marginal facies of the Taft Granite (Fig. 4). Herein, it is referred to as tonalite of the Gray Bands. The diorite of North America comprises a series of steeply dipping mafic dikes that derives its name from the resemblance of its exposure to the continent of North America (Fig. 3). It displays high compositional and textural variability but is largely Al-rich hornblende gabbro and diorite (Ratajeski et al., 2001). Precise dating of the diorite of North America has proven difficult because of Pb-loss and inherited zircons, but it is spatially associated with the Taft Granite, and they are interpreted to be coeval because the contacts of the diorite with the Taft Granite are diffuse and often grade into schlieren (Ratajeski et al., 2001).

Intrusive Suite of Buena Vista Crest The intrusive suite of Buena Vista Crest mostly crops out south of the ISYV and, in some areas, intrudes it (Fig. 2). Bateman (1992) recognized this suite as normally zoned, comprising several successively younger inward map units. One unit, the Granodiorite of Ostrander Lake, was discordantly dated at ca. 112 and 107 Ma (Stern et al., 1981), and the granodiorite of Illilouette Creek was dated at 99 ± 1 Ma (Tobisch et al., 1995). Reconnaissance mapping (B. Law, 2010, personal commun.) suggested that another unit of the intrusive suite of Buena Vista Crest, the Leaning Tower Granite, crops out on El Capitan. It is a medium-gray, medium-grained rock with distinctive biotite and hornblende clusters ~10 mm in diameter. Bateman (1992) mapped it as a marginal facies of the intrusive suite of Buena Vista Crest and inferred that it was coeval with the granodiorite of Illilouette Creek. The type locality for this unit is located on the south side ofYosemite Valley in the Cathedral Rocks area (Fig. 2), and Calkins (1985) did not map it in the vicinity of El Capitan.

METHODS Supplemental Figure. Sample photographs. Please visit http://​dx​.doi​.org​/10​.1130​/GES01133​.S1 or the full-text article on www​.gsapubs​.org to view the Supplemental File. 1

GEOSPHERE  |  Volume 11  |  Number 4

Mapping Mapping was conducted using several data sets and techniques. We employed remote sensing using light detection and ranging (LiDAR) point-cloud

and return strength data, high-resolution gigapixel photographs of the southeast face taken by xRez Studios (www​.xRez​.com) and, as part of this investigation, photographs of rock texture taken by rock climbers as they ascended the cliff, and high-resolution photographs taken of the cliff face taken from El Capitan Bridge by climbing photographer Tom Evans. We made direct examination of the face by rappelling the Prophet and the Nose and climbing the Muir Wall, New Dawn, Zodiac, Freeblast, East Buttress, and lower half of the North America Wall (Fig. 3). We constructed gigapixel photographs in May 2012 using a Gigapan robotic camera mount with a Nikon D5000 SLR and a 300 mm lens. These photographs were taken from the East Buttress of Middle Cathedral Rock, 1200–1500 m from the mapped face, at look-up angles of –6° to 28°, typically in flat light. Theoretical resolution with this setup is 2.2–2.7 cm/pixel and is consistent with resolution estimated from the photographs (e.g., 10 mm climbing rope is easily visible, and a climber’s helmet is typically 6–7 pixels wide). For photographs by Tom Evans­, the theoretical resolution is ~1 cm/pixel, but these images are significantly more oblique (typical look-up angles of 12°–39°). Mapped contacts are accurate to within 10 cm within the frame of reference of individual photographs, but all photographs are subject to camera distortion. Gradational contacts on El Capitan are on decimeter scale and are visible with this camera technology. The map was constructed using geographic information system (GIS) software. Contact lines of different units were manually digitized over a gigapixel image of the southeast face. These polygons were assigned rock types by evaluating the rock texture visible in close-up photographs of the rock taken by climbers (Fig. 5). Where contacts were obscured by shadows, lichen, surface encrustation, or photo-stitching errors, Tom Evans’ photographs were examined because they were taken under a variety of lighting conditions, from different vantage points with a different perspective, and often show contacts better than gigapixel imagery.

Mineral Abundance and Grain Size Photographs taken by climbers on the southeast face presented the means to study vertical changes in rock texture. Using the Exelis ENVI image processing package, mineral types were classified using simple quantitative thresholds in pixel value for 78 photographs taken over much of the extent of the El Capitan Granite (Supplemental Figure1). Images were classified in accordance with the distribution of biotite and hornblende (black-brown), feldspars (whitepink), and quartz (gray). Only photographs of fresh faces with no shadows were selected for this analysis. For each mineral type, contiguous regions representing individual crystals, defined using a 4-connect neighborhood, were automatically identified. One-pixel groups were ignored. From these classifications, the relative mineral group abundances and mean crystal sizes were calculated. To verify the accuracy of this method, a point count was conducted on six of the analyzed photographs. The manually counted relative mineral abundances were within ±5.1% of the automatically calculated values.

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B

A SUPPLEMENTAL TABLE 1. MAJOR ELEMENT DATA DETERMINED BY XRF Sample number BRO-02 EB-01

Rock type

Relative elevation (m)!

Kap

SiO 2 (wt%)

TiO 2 (wt%)

77.15

0.079

NA

Kap

ECT-01 ECT-02

354

Kt

76.67

272

Kap

75.94

315

76.43

0.05 0.09 0.07

Al 2 O 3 (wt%) 12.79 12.83 13.06 13.54

Fe 2 O 3 T (wt%) 0.97 0.52 1.23 0.79

MnO (wt%) MgO (wt%) CaO (wt%) Na2 O (wt%) K 2 O (wt%) 0.014

0.14

0.02

1.08

0.01

0.04

0.41

0.14

0.02

1.08

0.21

1.31

2.78 2.67 2.96 3.66

5.67 6.80 5.35 4.30

P2 O 5 (wt%)

Sum

0.07

100.743

0.00 0.02 0.00

Loss on ignition

99.96 99.91 100.32

N.D. 0.34 0.23 0.23

Location description" 10 m right of Rixon's Pinnacle Right The East Buttress, belay 4 El Capitan Tree , belay 3 El Capitan Tree , belay 5

ECT-04

Kec

308

75.07

0.29

13.69

2.51

0.05

0.71

3.29

3.83

1.01

0.04

100.49

0.38

El Capitan Tree , belay 7

ECT-06

Kap

292

77.04

0.03

13.23

0.58

0.02

0.04

0.88

3.86

4.58

0.00

100.25

0.18

El Capitan Tree , 20 m down the first rappell

ECT-07 FS-01

Kec

230

Kap

FS-02

75.75

224

Kt

FT-01

74.77

222

Kap

HLR-01 HLR-02

NA

Kec

239

Kec

163

0.09 0.09 0.041 0.26

13.39 14.46 13.62 12.78 14.93

1.02 0.72

0.03

0.09

0.02 0.03 0.017

0.91

0.08

0.93

0.04

0.05

0.74

0.50

0.05

1.92

0.44

3.51 3.61 3.08 3.36

4.71 5.96 5.76 5 4.58

0.00 0.00 0.00 0.00

99.66 100.11 100.06 97.908

0.02

100.42 100.34

0.04 0.44 0.33 N.D.

El Capitan Tree, 40 m down the secoN.D. rappel The Footstool, left side of summit The Footstool, 4 m below right side of summit 271045, 4181409 Heart Ledges rappel line, 1st station

Lower Cathedral Rock, float 10 m below Jungle Boogie

0.06

99.37

0.27

Lower Cathedral Rock, Overhang Bypass start

3.52

0.06

100.43

0.38

Kec

94

Kt

71.67

813

Kec

76.25

360

72.00

451

Ktn

74.81

457

67.18

0.21 0.15 0.30 0.24 0.60

14.91 13.42 15.14 13.42 16.65

1.99 1.46 2.42 2.00 4.37

0.06

0.45

0.03

1.89

0.24

0.05

1.31

0.65

0.04

2.25

0.47

0.09

1.92

1.08

3.47

3.79 3.17 3.58 3.24 4.26

4.38 4.38 4.00 3.75 2.57

0.02 0.02 0.05 0.02 0.13

100.43 99.91 100.41 100.64 99.92

0.53

Heart Ledges rappel line, 3rd station

0.40

3.88

3.41

Kec

99.55

0.37

100.11

3.25

3.11

ME-02

0.06

0.33

0.11

3.02

1.17

3.71

3.53

0.03

1.02

0.08

MW-01

3.44

3.72 2.92

0.06

3.81

0.06

3.07

3.56

3.27

15.07

MW-02

1.11

3.47

3.43

15.39

0.44

3.34

0.06

1.81

0.97

0.41

69.43

15.96

3.20

1.10

0.03

0.92 1.02 2.14

69.18

Na

0.48

14.95

1.99

NA

69.36

0.41

13.68

NA

Klt Klt

MW-03

70.61

0.22

Klt Kbv

LJ-01

NA

0.03

75.40 74.91 72.16 74.64

LC-01 LC-02 LC-05 LC-06

0.52 0.25 0.50 0.53 0.28

Lower Cathedral Rock, float 10 m below Jungle Boogie

Lower Cathedral Rock, 10 m right of EN.D. of the Line Left side of the summit of Little John Mescalito, belay 26 Muir Wall , belay 12 Muir Wall , belay 15 Muir Wall , belay 15

MW-04

Ktn

529

66.03

0.59

17.38

4.48

0.12

1.37

4.02

4.57

1.95

0.14

100.58

0.58

Muir Wall , belay 18

MW-05

Kec

546

72.66

0.27

14.37

2.46

0.04

0.65

2.35

3.52

3.57

0.04

100.23

0.29

Muir Wall , belay 19

MW-06

Ktn

MW-07

589

Kec

MW-08

74.24

688

Kt

MW-11

73.85

654

Kt

MW-10

61.25

628

Kt

MW-09

76.41

727

Kt

76.78 74.13

0.78 0.18 0.18 0.12 0.15

19.34 14.36 13.95 13.10 12.94 14.14

5.30 1.70 1.70 1.68 1.36 1.45

0.06

1.81

0.04

5.80

0.41

0.02

2.03

0.28

0.03

1.77

0.19

0.03

1.35

0.18 0.22

4.13 3.42 3.30 3.14

1.90 4.16 4.27 4.59

0.21

99.73 100.46

0.00

100.39

0.00 0.00

99.75 99.14

0.33 0.30 0.49 0.35 0.24

Muir Wall , belay 21 Muir Wall , belay 23 Muir Wall , belay 24 Muir Wall , belay 27

100.21 100.09

0.31

Quo Vadis, belay 21

3.29

0.11

0.85

2.83

4.32

2.39

0.09

100.56

0.26

Muir Wall , belay 32

13.84

1.74

0.04

0.42

1.94

3.63

3.60

0.03

99.99

0.25

North America Wall, belay 4

0.66

2.03

3.65

4.45

0.04

99.88

0.44

North America Wall, belay 5

3.20

4.74

0.41

Muir Wall , belay 22

0.01 0.00

15.76

0.18

1.16

4.80

0.02

13.20

0.42

74.66

0.16

3.42

3.93

0.13

70.16

307

0.03

1.39

3.70

75.15

823

Kec

1.39

0.05

1.25

800

Kt

NAW-01

MW-12

760

0.14

Kt

MW-13 NAW-02

Kec

333

71.95

0.27

15.00

2.46

0.07

NAW-03

Kec

366

73.88

0.30

13.51

2.66

0.05

0.71

2.24

3.32

3.27

0.04

100.06

0.31

NAW-04

Kec

415

70.78

0.28

15.38

2.50

0.04

0.65

2.50

3.46

4.24

0.05

100.15

0.31

NED-01 NED-02 NED-03 NED-04 NED-05

Kec

126

Kec

74.64

244

Kec

76.06

322

Kec

71.40

358

75.42

0.21 0.24

13.57 12.06 15.21

1.89 2.19 2.22

0.04

0.42

0.06

1.75

0.50

0.05

0.74

0.54

2.05

0.59

3.31 2.13

4.22 6.14 4.32

0.02 0.03 0.03

99.85 100.06 99.06 100.46

0.22 0.41 0.19 0.34

North America Wall, belay 6 North America Wall, belay 8 New Dawn, belay 1 New Dawn, belay 4 New Dawn, belay 7

4.27

0.02

100.51

0.22

New Dawn, 30 m above belay 15

4.03

0.03

99.83

0.36

New Dawn, belay 17

NED-08

Kec

657

Kt

74.26

718

75.99

793

76.40

852

70.47

665

74.97

689

75.39

724

76.05

0.25 0.14 0.14 0.11 0.15 0.15 0.12

13.78 13.01 13.22 12.32 13.71 13.37 12.99

2.27 1.46 1.30 1.29 1.58 1.53 1.20

0.07

0.57

0.07

1.99

0.20

0.03

1.39

0.19

0.03

1.48

0.17

0.04

1.05

0.24

0.04

1.38

0.26

0.03

1.41

0.16

1.41

3.70 3.30 3.29 2.96 3.49 3.29 3.13

3.59 4.33 4.25 4.34 4.37 4.38 4.14

0.03 0.00 0.00 0.02 0.00 0.01

100.29 92.75 99.91 99.82 99.22 100.29

0.53

New Dawn, belay 8

100.06

3.56 3.80

Kt

4.12

0.03 0.03

1.77 2.06

Kt

3.71

3.89

0.50 0.48

Kt

1.84

3.77

0.06 0.05

Kt

0.48

3.15

2.11 1.99

Kt

0.06

1.63

14.14 14.79

NED-09

2.14

0.07

0.23 0.23

NED-10

14.38

2.36

73.79 72.59

NO-02

0.23

12.66

520 595

NO-03

72.09

0.25

Kec Kec

NED-12

455

0.27

NED-06 NED-07

NO-01

Kec

Quo Vadis, belay 20

0.32 0.40 0.13 0.30 0.35 0.28

99.85

Kt

791

76.38

0.13

13.12

1.45

0.03

0.20

1.27

3.31

4.41

0.00

100.13

0.53

The Nose, 10 m below belay 28

Kt

812

72.52

0.28

14.62

2.56

0.07

0.55

2.19

4.23

2.78

0.05

99.73

0.21

The Nose, belay 29

NO-06

Kt

847

75.73

0.12

13.49

1.30

0.03

0.16

1.11

3.03

5.18

0.00

Kec

175

73.78

0.19

13.93

1.89

0.05

0.42

1.77

3.49

4.20

0.02

NS-01

Klt

PRO-01 PRO-02 PRO-03

217

Kt

Kt Kap

68.30

572

Kt

75.83

523

Kt

PRO-04 PRO-06

76.78

479

77.97

428

75.64

335

76.18

0.57 0.07 0.11 0.11 0.08 0.02

15.03 13.26 12.86 12.01 13.77 13.50

4.10 0.95 1.34 1.43 1.09 0.45

0.08

1.53

0.03

3.64

0.09

0.02

1.00

0.13

0.04

1.33

0.13

0.03

1.08

0.10

0.02

1.14

0.00

0.68

3.25 2.81 2.73 2.71 3.13 3.34

3.39 5.87 5.06 4.70 5.51 5.85

0.09 0.00 0.00 0.00 0.00 0.00

99.98

0.50

The Nose, belay 31

0.18

The Nose, belay 4

99.62

0.70 0.64 0.24 0.29 0.43 0.45

Native Son, route start The Prophet, belay 14 The Prophet, belay 9 The Prophet, 1 m below belay 7 The Prophet, 20 m above belay 5 The Prophet, belay 3

PRO-07

Kt

301

75.58

0.13

13.14

1.37

0.03

0.18

1.33

3.00

4.87

0.00

99.63

0.44

The Prophet, 25 m above belay 2

PRO-09

Klt

242

67.83

0.59

15.27

4.33

0.08

1.66

3.81

3.46

2.91

0.13

100.05

0.67

The Prophet, route start

PRO-10 SW-01

Kt

243

Kec

SW-02

75.96

213

Kec

SW-03

73.52

285

Kap

SW-04

74.20

338

Kec

SW-05

75.76

334

Kec

74.63

287

72.79

0.15 0.21 0.19 0.09 0.20 0.12

12.95 14.16 13.80 13.63 13.99 14.43 13.16

1.29 1.92 1.87 1.11 1.73 2.42 1.31

0.03

0.19

0.05

1.29

0.44

0.05

1.67

0.45

0.04

1.91

0.15

0.05

1.18

0.39

0.06

1.71

0.63

0.04

1.95

0.30

1.26

2.93 3.28 3.50 3.47 3.42 3.52 3.28

4.82 4.78 3.70 4.74 4.35 4.03 4.45

0.03 0.02 0.02

99.67 100.16 100.48

0.00

100.14

0.02

100.20

0.04

99.87

0.04

100.11

0.32 0.29 0.25 0.39 0.35 0.15 0.22

The Prophet, 10 m right of the start of the route Salathe Wall , belay 6 Salathe Wall , belay 8 Salathe Wall , belay 10 Salathe Wall , belay 10 Salathe Wall , belay 11

Kec Kec

309

76.51

0.13

12.78

1.33

0.04

0.18

1.10

3.02

4.76

0.03

99.85

0.44

Zodiac , belay 3

Kt

337

75.63

0.12

13.51

1.22

0.04

0.14

1.12

3.23

5.08

0.02

99.68

0.53

Zodiac , belay 4

Kap

412

75.59

0.032

13.32

0.91

0.204

0.02

0.6

3.76

4.8

0.00

99.236

N.D.

Zodiac , belay 7

ZO-05

76.22

0.28

ZO-01 ZO-02 ZO-03 ZO-06

277

Zodiac , belay 2

Klt

410

68.43

99.85

0.35

Zodiac , 10 m above belay 7

ZO-07

Kt

637

76.00

0.13

13.15

1.28

0.02

0.15

1.09

2.80

5.04

0.02

99.68

N.D.

Zodiac , belay 15

AGV-1 §

mean accepted

60.21 60.24

1.08 1.07

17.31 17.37

6.82 6.85

0.10 0.10

1.56 1.57

5.04 4.99

4.34 4.37

2.97 2.95

0.53 0.52

99.96 100.00

0.35

Mean of all samples

0.54

15.26

3.97

0.07

1.49

3.71

3.33

2.92

0.12

7

The Nose, belay 26

99.89 100.33 100.18 100.49 100.02 100.07

7

New Dawn, belay 19 New Dawn, belay 22 New Dawn, belay 25 New Dawn, belay 28 "The Nose", belay 24 The Nose, belay 25

0.00

NO-04 NO-05 NO-07

0.26

New Dawn, belay 11

C

s.d. 0.11 0.01 0.06 0.04 0.00 0.02 0.02 0.08 0.01 0.01 Note: Samples are stored in the collections of University of North Carolina, Chapel Hill Department of Geological Sciences, Chapel Hill, North Carolina 27599. Major element compositions are in weight percent. Major elements compositions express total Fe as Fe2O3 and have been normalized 100 wt% anhydrous. *The elevation, in meters, above the lowest point of exposed rock on the southwest face of El Capitan, near the start of the Nose (Figure 4) †

Most samples were taken from >500m cliffs, rendering GPS innacurate. Therefore, locations are described relative to climbing routes (Reed, 1996; Putnam and Sloan, 2014) as observed facing the cliff. UTMs given in NAD 1983 Zone 11S. § Results of 12 replicate analyses of USGS standard AGV-1.

Supplemental Table 1. Major element data deter­ mined by XRF. Please visit http://​dx​.doi​.org​/10​.1130​ /GES01133​.S2 or the full-text article on www​.gsapubs​ .org to view Supplemental Table 1. 2

SUPPLEMENTAL TABLE 2. TRACE ELEMENT DATA DETERMINED BY XRF Sample number

Rock type

Host rock*

Relative elevation (m) !

Ni (ppm)

Cu (ppm)

Zn (ppm)

BRO-01

Kap

Ks

N.A.

0.00

2.00

12.40

169.01

BRO-02

Kap

Khd

N.A.

2.00

0.80

Rb

(ppm) Sr

(ppm) Y 87.82

(ppm) Zr

(ppm) 26.80

1.74

22.90

Nb (ppm) 0.90

Ba (ppm)

Th (ppm)

78.67

17.80

76.66

22.50

2.07

10.40

The East Buttress, belay 4

8.00

El Capitan Tree , belay 5

5.80

El Capitan Tree , 20 m down the first rappell

6.10

269280, 4181129

Kd

N.A.

3.20

0.70

13.50

319.89

10.41

7.21

12.40

4.80

Kap

Kd

N.A.

0.80

0.80

15.50

90.77

124.81

17.21

60.90

10.80

ECT-06

Kap

Kd

N.A.

0.00

0.00

15.40

113.33

80.23

15.92

27.50

13.80

345.81

EGP-01

Kap

Kec

N.A.

1.70

0.80

10.00

170.67

187.65

26.52

25.40

31.40

1212.24

9.48

36.30

11.80

240.73

6.81

107.90

EGP-02

Kap

Kec

N.A.

0.00

Kap

Kec

N.A.

0.10

EL-02

Kap

Kec

FS-01

1.40

11.90

92.72

0.30

20.80

177.29

N.A.

1.30

0.60

14.80

187.51

Kt

N.A.

4.20

0.00

12.50

129.14

FS-03

Kap

Kt

N.A.

1.80

4.90

19.60

130.95

FT-01

Kap

Kec

N.A.

3.10

2.70

10.80

164.23

FT-02

Kap

Kec

N.A.

2.60

3.10

11.30

146.20

FT-03

Kap

Kec

N.A.

3.20

6.70

11.50

152.03

23.89

FT-04

Kap

Kap

Kec

N.A.

1.10

1.00

10.60

140.68

39.44

LE-01

Kap

ME-01

Kt

Kap

NED-11 NF-01

N.A.

Kt

Kap

N.A.

Kt

Kap

NO-02

N.A.

Khd

N.A.

0.30 0.30 0.90 0.00

0.90 0.00 1.40 5.90

23.00 10.30 13.60 10.80

147.53 125.04 126.82 165.73

East Ledges Decent, first rappel station

32.60

East Ledges Decent, 20 m left of the third rappel

261.60

5.30

The Footstool, left side of summit

14.60

448.29

7.50

3 m up Wyoming Sheep Ranch

39.50

14.00

49.87

34.10

271045, 4181409

9.80

512.24

45.00

270765, 4181945

12.42

21.42

32.65 22.81

101.20

20.54

28.60

15.40

58.52

29.70

271047, 4182592

6.83

0.00

4.10

96.72

13.10

270861, 4183146

84.94 59.74 56.40 121.98

12.14 9.08 22.74 2.13

23.20

0.00

14.51

91.22

39.30 17.20 34.30 55.30

22.00 7.10 15.20

596.27 114.37 168.07

10 m left of N.A.tive Son start

9.40

The Prophet, belay 3

8.60

40 m right of The Prophet start

14.42

152.00

141.90

312.90

23.85

201.00

N.D.

2.80

19.30

159.96

50.73

16.02

26.80

12.50

3.30

0.00

15.30

305.19

9.27

6.58

27.20

2.20

20.35

N.A.

1.40

1.40

19.70

135.72

59.86

17.22

28.60

9.70

284.04

Kap

Khd

Kap

Khd Khd

Kap

Khd

Kap

Kgp

N.A. N.A. N.A.

1.70 0.80 1.30

1.80 4.90 2.90

19.80 20.50 17.00

180.20

223.20

172.88

225.37

169.66

227.87

3.12

32.70 35.80

2.00 0.80

395.19

19.30

400.57

16.80 16.70

The Royal Arches, belay 7

82.18

18.02

51.20

15.80

159.62

147.01

16.57

66.10

18.90

751.49

32.80

105.95

204.69

10.98

72.00

15.60

1083.92

8.40

0.90

15.20

85.68

96.64

7.79

18.10

3.90

260.38

20.20

10m up the Wall of Early Morning Light

10

2.00

N.D.

31.85

26.76

El Cap Slab - near ESC-01

274737, 4181089

18.50 11.90

20 m left of rust streak the Waterfall Route start

8.10

South Seas start

30 m right Rhombus Wall talus summit

Salathe Wall , belay 10

Kt

N.A.

165.44

201.34

9.39

1244.64

Kec

N.A.

0

N.D.

N.D.

N.D.

119.00

216.00

N.D.

N.D.

N.D.

806.00

36.10

Start of the Nose

Kap

Kd

N.A.

6.60

0.00

8.40

429.69

28.42

52.45

87.00

23.20

83.15

18.20

Zodiac , belay 6

ZO-05

Kap

Kd

24.40

Zodiac , belay 7

YOS-1

AGV--1**

N.D.

93.74 464.76

YOS-180 # ZO-04

#

9.23

21.40

The Royal Arches, belay 9

147.60

21.80

0.00

0.30

3.00

34.96

274008, 4181083

21.60

4.60

0.20

30.00

1.50

575.32

0.10

1.90

N.A.

2.49

27.80

0.00

1.50

N.A.

Kec

85.77

3.63

31.90

19.90

N.A. N.A.

Kec

Kap

165.08

39.94

3.89

5.70

0.40

Kt Kec

Kap

10.70

277.34

1.88

1.70

N.A.

Kap Kap

WOEML-01

RHO-01

17.90

216136, 4178441 The Nose, belay 25

SW-03

RS-01 SS-02

N.A.

Start of Lunar Eclipse

The Nose, belay 29

6.20

391.85

N.D.

0.70

N.A.

Kt

20.20

New Dawn, belay 28

19.00

155.94

N.D.

N.A.

Kt

N.A.

4.10

1.80

19.80

345.88

0.00

35.83

95.50

16.20

4.09

mean

17.5

N.A.

N.A.

73.2

704.0

21.0

280.0

18.8

1164.0

accepted

19.0

68.6

658.0

20.0

230.0

15.0

1140.0

6.1

s.d.

4.9

0.6

0.2

3.6

0.3

4.6

0.7

10.3

Figure 5. Example of mapping methods. (A) and (B) are the area around the 7th belay on Tangerine Trip (Fig. 3), which is indicated by the circled 7 on both images. Note the climbers around the belay for scale. (A) High-resolution image with the contacts of units digitized. (B) Map displays the assigned units. Pink is El Capitan Granite (Kec); light green is dikes of the Oceans (Kdo); and dark green is the diorite of North America (Kd). Light-yellow lines are aplite dikes, and the thick dark red line is the path of the climbing route. (C) Photograph taken at this location courtesy of www​.xRez​.com.

Mescalito, belay 26

28.00

891.46 252.39

N.D.

812

Klt

Kap

Kap

9.20

184.52 2032.64

N.A. N.A.

Kap

RA-04

6.10 10.40

0.00 N.D.

Kt Kt Kap

PRO-08 RA-01

N.D.

268756, 4180619

34.60

33.80

7.50

33.20

3.34

76.21

NO-05

RA-02

N.D.

26.00

13.25

0.00

23.00

40.21

PRO-06

2.00

Location description§ Lower Brother, 30 m right of Positively 4 th Street 10 m right of Rixon's PinN.A.cle Right

107.58

NS-02

RA-03

689

92.20 12.06

0.00

472.31

134.68

Kap

ECT-02

EL-01

82.29

2.54

15.90

EB-01

9.3

Note: Samples stored in the collections of University of North Carolina, Chapel Hill Department of Geological Sciences, Chapel Hill, North Carolina 27599. Trace element compositions in parts per million (ppm). N.A. = not available, N.D. = not determined *The rock in which the aplite dike is hosted. N.A. if the sample is not an aplite. † The elevation, in meters, above the lowest point of exposed rock on the southwest face of El Capitan, near the start of the Nose (Figure 4) § Most samples were taken from >500m cliffs, rendering GPS innacurate. Therefore, locations are described relative to climbing routes (Reed, 1996; Putnam and Sloan, 2014) as observed facing the cliff. UTMs given in NAD 1983 Zone 11S. # From Ratajeski et al., 2001 **Results of 4 replicate analyses of USGS standard AGV-1

Supplemental Table 2. Trace element data determined by XRF. Please visit http://​dx​.doi​.org​/10​.1130​ /GES01133​.S3 or the full-text article on www​.gsapubs​ .org to view Supplemental Table 2. 3

SUPPLEMENTAL TABLE 3. ICPMS DATA (ppm) Co (ppm) Cu (ppm) Zn (ppm) Ga (ppm) Ge (ppm) Rb (ppm) Sr (ppm) Y ±5 ±1 ± 10 ± 30 ±1 ± 0.5 ±1 ±2 13 1 B.D.L. B.D.L. 15 2.0 132 89 7 B.D.L. 20 B.D.L. 15 3.0 150 25 24 4 B.D.L. 40 16 1.8 127 216 25 4 10 50 13 2.0 172 170 25 3 10 50 17 1.8 133 259 27 3 10 60 16 1.5 133 174 24 3 10 60 16 1.9 137 226 24 3 10 50 16 1.8 132 196 23 3 B.D.L. 50 17 1.7 138 288 28 3 20 50 16 2.1 125 230 12 2 B.D.L. 40 15 1.5 110 213 15 1 10 B.D.L. 14 1.3 102 335 12 1 10 40 14 1.4 114 207 13 1 10 B.D.L. 14 1.7 142 247 7 B.D.L. 10 18 3.5 30 328 4 Note: Samples stored in the collections of University of North Carolina, Chapel Hill Department of Geological Sciences, Chapel Hill, North Carolina 27599.

Sample number BRO-02 FT-01 NED-01 NED-02 NED-03 NED-04 NED-05 NED-06 NED-07 NED-08 NO-01 NO-03 NO-04 NO-06 ZO-05

Rock type Kap Kap Kec Kec Kec Kec Kec Kec Kec Kec Kt Kt Kt Kt Kap

Host rock* Khd Kec N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. Kd

Relative elevation (m)! N.A. N.A. 126 244 322 358 455 520 595 657 665 724 791 847 N.A.

Sc (ppm) Be (ppm) V "1 ±1 B.D.L. 1 2 3 3 2 3 1 3 2 4 2 3 2 4 2 3 2 5 2 3 1 1 1 2 1 2 2 3 3

(ppm) Zr (ppm) ± 0.5 ±1 1.1 49 34.8 77 9.6 148 12.7 145 13.6 138 13.5 169 15.7 141 13.8 133 12.7 138 23.3 143 8.0 111 10.2 107 8.3 89 8.5 91 38.8

108

*The rock in which the aplite dike is hosted. N.A. if the sample is not an aplite. †

The elevation, in meters, above the lowest point of exposed rock on the southwest face of El Capitan, near the start of the Nose (Figure 4)

§

Most samples were taken from >500m cliffs, rendering GPS innacurate. Therefore, locations are described relative to climbing routes (Reed, 1996; Putnam and Sloan, 2014) as observed facing the cliff. UTMs g

Supplemental Table 3. ICPMS data. Please visit http://​dx​.doi​.org​/10​.1130​/GES01133​.S4 or the fulltext article on www​.gsapubs​.org to view Supplemental Table 3. 4

GEOSPHERE  |  Volume 11  |  Number 4

Sample Collection

Whole-Rock and Trace-Element Geochemistry

Samples of all units were collected from the base, summit, and face of El Capitan and from the base of Lower Cathedral Rock on the south side of Yosemite Valley (Supplemental Figure [see footnote 1], Supplemental Tables 12 and 23). Samples (typically ~500 g) from the face were primarily collected from belay stances on climbing routes at sites that had no impact on the climbing route. Specific climbing routes were selected for sampling to test for vertical variation because they passed through large extents of single units. Samples were collected from areas interpreted to be representative of the unit, and areas of significant evidence for mingling and mixing (Reid et al., 1983; Ratajeski et al., 2001) were avoided. The elevation of each sample from the southeast face of El Capitan was determined using a georeferenced terrestrial LiDAR point cloud and are accurate to within a meter. Additional aplite samples were collected along the walls of the valley from El Capitan east to North Dome (Fig. 2; Supplemental Table 2 [see footnote 3]).

Whole-rock and trace-element analyses were performed using wavelength-dispersive X-ray fluorescence (XRF) at the University of North Carolina at Chapel Hill on a Rigaku Supermini XRF spectrometer following powdering in a steel jaw crusher and ceramic shatter box. Loss on ignition was determined by heating ~2 g of rock powder to 950 °C for 1.5 h. Ignited sample (0.9000 ± 0.005 g) and 64.7% Li2B4O7, 35.3% LiBO2, 0.5% LiBr flux (8.1000 ± 0.005 g) were melted in a Pt crucible and fused into a glass bead. Trace-element analyses were performed with XRF using pressed-powder disks. Unignited samples (6.000 g) were combined with paraffin powder (0.600 g), mixed in a ball mill, and hydraulically pressed into an Al mold. Calibrations were run against standards AGV-1, G-2, QLO-1, RGM-1, GSP-2, NIST 278, MAG-1, BHVO‑1, and DNC‑1; accuracy and reproducibility are reported in Supplemental Tables 1 and 2 (see footnotes 2 and 3). Extended trace-element analyses were performed by Actlabs (Ontario, Canada), where samples were dissolved by Li2B4O7 /LiBO2 ­fusion and analyzed by ICPMS (Supplemental Table 34).

Putnam et al.  |  Plutonism in three dimensions

1139

Research Paper Tests for significance of correlation of chemical values with elevation were performed using a 2-tailed t-test a significance level p = 0.05.

Geochronology Eight samples were selected for zircon U-Pb geochronology by both l­aser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) and single-grain isotope dilution-thermal ionization mass spectrometry (TIMS). ­ Samples were selected for geochronology from units on and around El Capitan in order to evaluate the timing of the mapped intrusive events. Of particular interest was the Leaning Tower Granite as there was no published date for the unit and knowing its age would help resolve the timing of the intrusions exposed on the southeast face of El Capitan. All samples were broken down using a jaw crusher and a disc mill. Zircons were separated using standard density (water table and heavy liquids) and magnetic techniques. Samples selected for LA-ICPMS dating include: El Capitan Granite from the Cookie Slide near the west entrance to Yosemite Park (CS720; 63 zircons) and the summit of El Capitan (ECS726; 28 zircons); Taft Granite (ECS‑01; 14 zircons); Leaning Tower Granite from the base of Lower Cathedral Rock, the type locality of the unit (LC-01; 27 zircons); Bridalveil Grano­ diorite (LC-02; 39 zircons); granite from near El Portal (presently mapped as El Capitan Granite [Huber et al., 1989] but texturally distinct at the sample location; RF-01; 26 zircons); diorite of the Rockslides (YOS-23C; 38 zircons); and diorite of North America (YOS-104; 36 zircons). Grains representative of the population’s size and morphology were separated from each sample, mounted in epoxy, polished using standard polishing techniques, and mapped by backscattered electron and monochromatic cathodoluminescence imaging on a scanning ­ electron microscope. Operating procedures for LA-ICPMS follow those outlined in Kylander-Clark et al. (2013). Spot analyses were run at 4 Hz for 15–20 seconds; spot sizes ranged from 15 to 24 µm in diameter and 6–8 µm deep. Isotopic concentrations were measured on the Nu Plasma, with 238U and 232Th on Faraday detectors, and 208Pb, 207Pb, 206Pb, and 204Pb concentrations were measured on ion counters. Isotopic ratios and standard correction were performed using Iolite (Paton et al., 2010), using the 91500 zircon (1065 Ma; Wiedenbeck et al., 1995) as the primary reference material; GJ1 (602 Ma; D. Condon, 2010, personal commun.), Plešovice (337 Ma; Sláma et al., 2008), SL1 (564 Ma; G ­ ehrels, 2000), and Temora2 (417 Ma; Black et al., 2004) were also measured for quality control. We consistently obtained weighted mean 206Pb/ 238U ages within 1% of the reference value for each of the secondary reference materials (605.5 ± 1.8 Ma (n = 52), 560.8 ± 5.0 Ma (n = 6), 340.2 ± 1.8 Ma (n = 20), 418.9 ± 5.4 Ma (n = 3) for GJ1, SL1, Plešovice, and Temora2, respectively, and thus conservatively add 1% in quadrature to the final age of each sample. The analytical uncertainty is expressed first, followed by the propagated uncertainty in brackets for each sample. All errors are 2s unless expressed otherwise. Three samples dated by LA-ICPMS were also dated by ID-TIMS: the El Capi­ tan Granite at the Cookie Slide and El Capitan’s summit (CS720 and ECS726,

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respectively) and the Leaning Tower Granite (LC-01). Zircon grains were thermally annealed at 900 °C for 48 h and were chemically abraded in 29M HF for 16 h at 220 °C to remove mineral inclusions and zones affected by radiation damage that are subject to Pb-loss (Mattinson, 2005). Fractions were spiked with a 205Pb-233U-236U tracer (Parrish and Krogh, 1987) and dissolved in 29M HF following a procedure modified after Krogh (1973) and Parrish (1987). Anion exchange (HCl) column chromatography was used to isolate U and Pb from the dissolved solution. Analyses of U and Pb were completed using a VG Sector 54 thermal ionization mass spectrometer at the University of North Carolina at Chapel Hill. Uranium was run on single Re filaments either as a metal, after loading in graphite and H3 PO4 , or as an oxide, after loading in silica gel. Lead was loaded in silica gel on single, zone-refined Re filaments. Both U and Pb were analyzed in single-collector peak-switching mode using a Daly ion-counting system. Data processing and age calculations were completed using the applications Tripoli and U-Pb_Redux developed as part of the EARTHTIME initiative (Bowring et al., 2011; McLean et al., 2011). Decay constants used were 238 U = 1.55125 × 10–10 a–1 and 235U = 9.8485 × 10–10 a–1 (Steiger and Jäger, 1977). Corrections for initial Th/U disequilibrium (Mattinson, 1973; Schmitz and Bowring, 2001) for the ID-TIMS samples were made using U-Pb_Redux (corrections are much smaller than the uncertainties in LA-ICPMS ages). An ­assumed magmatic Th/U ratio of 4 was used based on an average Th/U r­ atio of grano­dio­rites in the Sierra Nevada batholith drawn from the NAVDAT data­ base (www​.navdat​.org). The difference between an uncorrected 206Pb/ 238U weighted mean age and an age that has been corrected for a magmatic Th/U ratio of 4 is ~95 ka in these samples.

RESULTS Field Relations The new mapping (Fig. 6) reveals field relations that help to resolve an intrusive history previously obscured by problematic geochronology and physical inaccessibility. The oldest and most extensive intrusion, the El Capitan Granite, is homogenous in outcrop, with little obvious modal layering. On the southeast face, magmatic fabric is rare and, where present, poorly developed. Mafic enclaves are uncommon (occupying less than 0.01 area%) and typically small (