1
SUPPLEMENTARY MATERIAL
2
3
1. Analytical Procedures
4
5
1.1 Major and Trace Element Analysis
6
7
New whole rock, major and trace element data for 19 fresh, medium- to coarse-
8
grained, equigranular samples from the Eastern Karakoram are presented. The data
9
are interpreted with respect to the available data for the Eastern Karakoram (Sinha et
10
al., 1999; Uphadhyay et al., 1999) and compared with magmatic rocks from the
11
Karakoram, the High Himalaya, the Trans-Himalaya belt and Southern Tibet (Allègre
12
& Othman, 1980; Crawford & Searle, 1992; Crawford & Searle, 1993; Crawford &
13
Windley, 1990; Debon et al., 1987; Debon & Khan, 1996; Deniel et al., 1987;
14
Honneger et al., 1982; Inger & Harris, 1993; Le Fort et al., 1983; Miller, 1999;
15
Petterson & Windley, 1985; Petterson & Windley, 1991; Rex et al., 1988; Schärer et
16
al., 1990; Searle et al., 1992; Searle et al., 1997; Thow, 2004; Vidal et al., 1982 &
17
1984).
18
19
Samples were analysed for major and trace element abundances by XRF spectrometry
20
at the Open University. REE data were obtained by ICP-AES at Oxford Brookes
21
University and by ICP-MS at the University of Oxford (see Table S1B caption for
22
details of samples analysed at each institution). Type-samples were selected to
23
represent each formation based upon petrology, field relations and sample quality.
24
25
1.2 Isotope Geochemistry Analysis
26
27
The Sm-Nd analyses were undertaken at NERC Isotope Geosciences Laboratory
28
(NIGL). Prior to analysis, the samples were spiked with
29
decomposed using HF and 2-3 drops of HNO3 in sealed Teflon™ bombs heated to
30
120°C. After additional treatment with HNO3 the samples were converted to a
31
chloride by the addition of 6M HCl. Separation of Sr and REE from the chloride
32
solution was achieved by standard ion exchange using Biorad® AG50W-X8 ion
33
exchange resin. Reverse-ion chromatography was then used to separate Sm and Nd
34
from the REE. The columns for this procedure contained di-2-ethylhexyl
150
Nd and
147
Sm tracers and
1
35
orthophosphoric acid (HDEHP)-coated Biobeads®. Procedural blanks were < 300 pg
36
for Sr and < 130 pg for Nd.
37
38
All isotope ratios were measured using a Finnegan-MAT 262 mass spectrometer at
39
NIGL. The analytical data are presented in Table S2. The analytical uncertainties in
40
isotope ratios are ±0.01% for
41
and
42
146
43
Johnson and Matthey® Nd standards were run for each sample batch and provided a
44
mean
45
0.511199 ± 0.000024 (2σ, n =23, batch 512). These values are considered rather high
46
and relate to a period during which an unexplained bias in the
47
introduced into the mass-spectrometric analysis. Following laboratory practice, the
48
results have been corrected to a value of 0.511124 for J & M, which corresponds to
49
0.511864 for the La Jolla international standard. Replication of an
50
standard gave a mean of 0.710256 ± 0.000018 (2σ, n = 29, batch 505 & 506) and
51
0.710249 ± 0.000023 (2σ, n =49, batch 512).
87
143
Nd/144Nd and 87Rb/86Sr, and ±1.00% for
Rb/86Sr. Mass fractionation of
Nd/144Nd = 0.7219 and
143
87
143
147
Sm/144Nd
Nd/144Ndmeasured was corrected relative to
Sr/86Srmeasured corrected relative to
86
Sr/88Sr = 0.1194.
Nd/144Nd ratio of 0.511199 ± 0.000017 (2σ, n =36, batch 505 & 506) and
143
Nd/144Nd ratio was
87
Sr/86Sr NBS 987
52
53
1.3 Coupled LA-MC-ICP-MS & ID-TIMS U-Pb data analysis methodology
54
55
The analytical work for absolute age determination, using both Isotope Dilution –
56
Thermal Ionisation Mass Spectrometry (ID-TIMS) and laser ablation multi-collector
57
inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was undertaken at
58
the NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth,
59
UK.
60
61
ID-TIMS analyses were analysed following conventional techniques (e.g. Krogh,
62
1973; Krogh, 1982; Parrish, 1987; Corfu & Noble, 1992; Noble et al., 1993) using a
63
205
64
Mass spectrometry data were reduced using the MS-DOS program ROCKAGE, an
65
algorithm based upon the numerical analysis and error propagation of Roddick (1987)
66
with decay constants defined by Jaffey et al. (1971). The plotting of reduced data onto
67
Concordia or Isochron diagrams was done using ISOPLOT 3.0 (Ludwig 2003).
68
Uncertainties quoted for all ages are 2σ. Corrections for common lead were made by
Pb-233U-235U-230Th mixed spike (Krogh & Davis, 1975; Parrish & Krogh, 1987).
2
69
determining the initial common lead values from K-feldspar within the sample for
70
fractions P8, P46, P113, P112, P175 and P142, with the Stacey-Kramers model
71
composition being generally satisfactory for the remaining cases (Stacey & Kramers,
72
1975). The U-Pb data are summarised in Tables S3-7 and are illustrated in Figures 4
73
& 6.
74
75
For dating via LA-MC-ICP-MS, the methodology of Horstwood et al. (2003) was
76
followed. Measurements were obtained using a Thermo-Elemental Axiom MC-ICP-
77
MS system that was coupled to a New Wave Research LUV266X Nd:YAG laser.
78
Instrumental mass bias and plasma-induced inter-element fractionation was corrected
79
by simultaneously aspirating a 205Tl/235U solution during measurements using a Cetac
80
Technologies Aridus desolvating nebulizer. All data obtained via in situ
81
measurements were reduced on an in-house spreadsheet with ages determined using
82
ISOPLOT 3.0 (Ludwig, 2003).
83
84
Prior to laser ablation, samples were not polished in order to optimise analysis of the
85
younger magmatic component. This is particularly important because examination via
86
ID-TIMS suggests the presence of inherited cores. Clearly, when grains are not etched
87
or polished it is important to scrutinise the data for Pb-loss on external surfaces.
88
Fortunately, Pb-loss is evident by varying the fluence of each analysis. By increasing
89
the fluence for subsequent analyses of individual grains, Pb-loss will be evident if the
90
data lack coherence with younger ages and associated greater common lead, this may
91
be particularly apparent for high U samples.
92
93
Supplementary References
94
95
Allègre, C. J., and D. B. Othman (1980), Nd-Sr isotopic relationship in granitoid
96
rocks and continental crust development: a chemical approach to orogenesis, Nature,
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286, 335-346.
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Batchelor, R. A., and P. Bowden (1985), Petrogenetic interpretation of granitoid rock
series using multicationic parameters, Chem. Geol., 43-55.
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3
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Corfu, F., and S. R. Noble (1992), Genesis of the southern Abitibi greenstone belt,
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Superior Province, Canada: Evidence from zircon Hf-isotope analyses using a single
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filament technique, Geochem. Cosmochem. Acta, 56, 2081-2097.
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106
Crawford, M. B., and M. P. Searle (1992), Field relationships and geochemistry of
107
pre-collisional (India-Asia) granitoid magmatism in the central Karakoram,
108
Tectonophysics, 206, 171-192.
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110
Crawford, M. B., and M. P. Searle (1993), Collision-related granitoid magmatism and
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crustal structure of the Hunza Karakoram, north Pakistan, in Treloar, P.J., Searle
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M.P., eds., Himalayan Tectonics, Geol. Soc. London Spec. Pub., 74, 53-68.
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Crawford, M. B., and B. F. Windley (1990), Leucogranites of the Himalaya /
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Karakoram: implications for magmatic evolution within collisional belts and the study
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of collision related leucogranite petrogenesis, Journal of Volcan. Geotherm. Res., 44,
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1-19.
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Debon, F., and N. A. Khan (1996), Alkaline orogenic plutonism in the Karakorum
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batholith: the Upper Cretaceous Koz Sar complex (Karambar valley, N. Pakistan),
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Geodinam. Acta, 9, 145-160.
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Debon, F., and P. Le Fort (1983), A chemical-mineralogical classification of common
124
plutonic rocks and associations, Trans. Roy. Soc. Ed.: Earth Sciences, 73, 135-149.
125
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Debon, F., P. Le Fort, D. Dautel, J. Sonet, and J. L. Zimmerman (1987), Granitoids of
127
western Karakoram and northern Kohistan (Pakistan): a composite Mid Cretaceous to
128
Upper Cenozoic magmatism, Lithos, 20, 19-24.
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Deniel, C., P. Vidal, and A. Fernandez (1987), Isotopic study of the Manaslu granite
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(Himalaya, Nepal) – inferences on the age and source of Himalayan leucogranites,
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Contrib. Min. Pet., 96, 78-92.
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DePaolo, D. J. (1981), Nd in the Colorado Front Range and implications for crust
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formation and mantle evolution in the Proterozoic, Nature, 291, 193-196.
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Honegger, K., V. Dietrich, W. Frank, A. Gansser, M. Thoni, and V. Trommsdorff
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(1982), Magmatism and metamorphism in the Ladakh Himalaya (the Indus-Tsangpo
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suture zone), Earth Planet. Sci. Lett., 60, 253-292.
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Horstwood, M. S. A., G. L. Foster, R. R. Parrish, S. R. Noble, and G. M. Nowell
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(2003), Common-Pb corrected in-situ U-Pb accessory mineral geochronology by LA-
143
MC-ICP-MS, Journal of Analytical Atomic Spectrometry, 18, 837-846.
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Inger, S., and N. Harris (1993), Geochemical constraints on leucogranite magmatism
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in the Langtang valley, Nepal Himalaya, J. Pet., 34, 345-368.
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Jaffey, A. H., K. F. Flynn, L. E. Glendenin, W. C. Bentley, and A. M. Essling (1971),
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Precision measurement of the half-lives and specific activities of U235 and U238, Phys.
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Rev., Series C4, 1889-1906.
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Krogh, T. E. (1973), A low contamination method for the hydrothermal
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decomposition of zircon and extraction of U and Pb for isotopic age determinations,
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Geochem. Cosmochem. Acta, 37, 485–494.
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Krogh, T. E. (1982), Improved accuracy of U-Pb zircon ages by the creation of more
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concordant systems using an air abrasion technique, Geochem. Cosmochem. Acta, 46,
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637-649.
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160
Krogh, T. E., and G. L. Davis (1975), The production and preparation of 205Pb for use
161
as a tracer for isotope dilution analyses, Carnegie Institution of Washington Yearbook,
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416–417.
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164
La Roche, H. de (1964), Sur l’expression graphique des relations entre la composition
165
chimique et la composition minéralogique quantitative des roches cristallines.
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Présentation d’un diagramme destiné à l’étude chimico-minéralogique des massifs
167
granitiques ou grano-dioritiques. Application aux Vosges cristallines, Sci. Terre, 9,
168
293-337.
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170
La Roche, H. de, J. Leterrier, P. Grandclaude, and M. Marchal (1980), A
171
classification of volcanic and plutonic rocks using R1R2-diagram and major element
172
analyses – its relationships with current nomenclature, Chem. Geol., 29, 183-210.
173
174
Le Fort, P., A. Michard, J. Sonet, J. L. Zimmerman (1983), Petrology, geochemistry
175
and geochronology of some samples from the Karakorum axial batholith, northern
176
Pakistan, in Granites of Himalaya, Karakorum and Hindu Kush, Inst. Geol. Punjab
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Uni. Press, edited by F.A. Shams, 377-387.
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179
Ludwig, K. R. (2003), Isoplot3, a geochronological toolkit for Microsoft Excel.
180
Berkeley Geochronology Center Special Publication No. 1a.
181
182
Miller, C., R. Schuster, U. Klotzli, V. Mair, W. Frank, and F. Purtscheller (1999),
183
Post-collisional potassic and ultrapotassic magmatism in SW Tibet: Geochemical, Sr-
184
Nd-Pb-O constraints for mantle source characteristics and petrogenesis, J. Pet., 40,
185
1399-1424.
186
187
Noble, S. R., R. D. Tucker, and T. C. Pharaoh (1993), Lower Palaeozoic and
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Precambrian igneous rocks from eastern England and their bearing on late Ordovician
189
closure of the Tornquist Sea: Constraints from U-Pb and Nd isotopes, Geol. Mag.,
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130, 835-846.
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192
Parrish, R. R. (1987), An improved micro-capsule for zircon dissolution in U-Pb
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geochronology, Chem. Geol., 66, 99-102.
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195
Parrish, R. R., and T. E. Krogh (1987), Synthesis and Purification of 205Pb for U-Pb
196
Geochronology, Chem. Geol., 66, 103-110.
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198
Petterson, M. G., and B. F. Windley (1985), Rb-Sr dating of the Kohistan arc-
199
batholith in the Trans-Himalaya of N. Pakistan, and tectonic implications, Earth
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Planet. Sci. Lett., 74, 45-57.
201
202
Petterson, M. G., and B. F. Windley (1991), Changing source regions of magmas and
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crustal growth in the Trans-Himalayas: evidence from the Chalt volcanics and
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204
Kohistan batholith, Kohistan, northern Pakistan, Earth Planet. Sci. Lett., 102, 326-
205
341.
206
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Rex, A. J., M. P. Searle, R. Tirrul, M. B. Crawford, D. J. Prior, D. C. Rex, and A.
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Barnicoat (1988), The geochemical and tectonic evolution of the central Karakoram,
209
North Pakistan, Phil. Trans. R. Soc. Lond., A326, 229-255.
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Roddick, J. C. (1987), Generalized numerical analysis with applications to
212
geochronology and thermodynamics, Geochem. Cosmochem. Acta, 51, 2129-2135.
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Schärer, U., P. Copeland, T. M. Harrison, and M. P. Searle (1990), Age, cooling
215
history and origin of postcollisional leucogranites in the Karakoram batholith, a
216
multisystem isotope study, J. Geol., 98, 233-251.
217
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Searle, M. P., M. B. Crawford, and A. J. Rex (1992), Field relations, geochemistry,
219
origin and emplacement of the Baltoro granite, central Karakoram, R. Soc. Edin.
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Trans., 83, 519-538.
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Searle, M. P., R. R. Parrish, K. V. Hodges, A. Hurford, M. W. Ayres, and M. J.
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Whitehouse (1997), Shisha Pangma leucogranite, south Tibetan Himalaya: field
224
relations, geochemistry, age, origin, and emplacement, J. Geol., 105, 295-317.
225
226
Sinha, A. K., H. Rai, R. Uphadhyay, and R. Chandra (1999), Contribution to the
227
geology of the Eastern Karakoram, India, in Himalaya and Tibet: Mountain Roots to
228
Mountain Tops, Geol. Soc. America Spec. Pub., vol. 328, edited by A. Macfarlane et
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al., 33-46.
230
231
Stacey, J. S., and J. D. Kramers (1975), Approximation of terrestrial lead evolution by
232
a two-stage model, Earth Planet. Sci. Lett., 26, 207-221.
233
234
Thow, A. (2004), Tectonic, Metamorphic and Magmatic Evolution of the Central
235
Karakoram Crust, Northern Pakistan, PhD thesis, University of Oxford, UK.
236
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237
Uphadhyay, R., A. K. Sinha, R. Chandra, and H. Rai (1999), Tectonic and magmatic
238
evolution of the Eastern Karakoram, India, Geodinam. Acta, 12, 341-358.
239
240
Vidal, P., J. Bernardgriffiths, A. Cocherie, P. Le Fort, J. J. Peucat, and S. M. F.
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Sheppard (1984), Geochemical comparison between Himalayan and Hercynian
242
leucogranites, Phys. Earth Planet. Int., 35, 179-190.
243
244
Vidal, P., A. Cocherie, and P. Le Fort (1982), Geochemical investigations of the
245
origin of the Manaslu leucogranite (Himalaya, Nepal), Geochim. et Cosmocim. Acta,
246
46, 2279-2292.
247
248
Figure Captions:
249
250
Figure S1A: R1R2 classification of plutonic rocks of the Eastern Karakoram. The
251
samples are grouped as co-magmatic granitoid suites on the basis of their field
252
relations, mineralogy and age. Table DR1 displays summary major and trace element
253
geochemical data for all samples. Weight percent silica contours based on data from
254
the CLAIR file. R1R2 axes, evolutionary trends and silica contours from La Roche et
255
al. (1980).
256
257
Figure S1B: Distribution of the Eastern Karakoram Granitoid samples in the
258
'characteristic minerals' diagram of Debon and Le Fort (1983). The parameters are in
259
gram-atoms x 103 in 100g of rock. ‘A’ is the 'aluminous index' whilst ‘B’ is
260
proportional to the mafic mineral content (La Roche, 1964). The samples are
261
separated between peraluminous (+ve A) and metaluminous (-ve A) fields. Typical
262
mineral components for each field are provided in sectors I-IV.
263
264
Figure S2: Classification comparison of the Eastern Karakoram Granitoids with pre-
265
and post-collisional granitoids from the Karakoram, Ladakh and Kohistan. A)
266
Miocene plutonic rocks of the Eastern Karakoram and the Baltoro Plutonic Unit; B)
267
Pre-collisional plutonic magmatism of the Eastern Karakoram and the main
268
Karakoram Axial Batholith; C) Pre-collisional plutonic magmatism of the Ladakh-
269
Kohistan Trans-Himalaya Batholith. Weight percent silica contours based on data
8
270
from the CLAIR file. R1R2 axes, evolutionary trends and silica contours from La
271
Roche et al. (1980).
272
273
Figure S3: Comparison of the Eastern Karakoram Granitoids with pre- and post-
274
collisional granitoids from the Karakoram, Ladakh and Kohistan. A) Miocene
275
plutonic rocks of the Eastern Karakoram and the Baltoro Plutonic Unit; B) Pre-
276
collisional plutonic magmatism of the Eastern Karakoram and the main Karakoram
277
Axial Batholith; C) Pre-collisional plutonic magmatism of the Ladakh-Kohistan
278
Trans-Himalaya Batholith. Samples are plotted on the 'characteristic minerals'
279
diagram of Debon & Le Fort (1983). The parameters are in gram-atoms x 103 in 100g
280
of rock. ‘A’ is the 'aluminous index' whilst ‘B’ is proportional to the mafic mineral
281
content (La Roche 1964). The samples are separated between peraluminous (+ve A)
282
and metaluminous (-ve A) fields.
283
284
Figure S4: Tectono-magmatic discrimination comparison of the Eastern Karakoram
285
Granitoids with pre- and post-collisional granitoids from the Karakoram, Ladakh and
286
Kohistan. A) Miocene plutonic rocks of the Eastern Karakoram and the Baltoro
287
Plutonic Unit; B) Pre-collisional plutonic magmatism of the Eastern Karakoram and
288
the main Karakoram Axial Batholith; C) Pre-collisional plutonic magmatism of the
289
Ladakh-Kohistan Trans-Himalaya Batholith. Data is plotted on the R1R2 diagram of
290
La Roche et al. (1980). Tectono-magmatic fields (1-6) after Batchelor & Bowden
291
(1985).
292
293
Table Captions
294
295
Table S1: Major and Trace element data for Eastern Karakoram Granitoids. Values
296
provided for the diagrams of R1R2 classification and B vs A characteristic mineral
297
(Figures S1-4). Field locations (see Figures 1-3): MMC = Muglib Migmatite
298
Complex, TDL = Tangtse-Darbuk Leucogranites, NSL = Nubra - Siachen
299
Leucogranites, AD = Arganglas Diorites, TDG = Tangtse-Darbuk Granitoids.
300
301
Table S2: Rb-Sr and Sm-Nd data for EKG samples and representative KMC
302
metapelites (this study and Thow 2004). Ages for samples are determined by U-Pb
303
geochronology (this study), except for assumed ages (denoted by superscript ‘a’).
9
304
KMC ages based upon the M2 metamorphic ages of Thow (2004). Mantle separation
305
ages (TDM) were determined following the method of DePaolo (1981).
306
307
Table S3: U-Pb ID-TIMS data for all data displayed on Concordia diagrams (Figure
308
4).
309
(1)
Rock-type: MCD (Mid Cretaceous Diorites); LCD (Late Cretaceous Diorites);
310
MMC (Muglib Migmatite Complex); TDL (Tangtse-Darbuk Leucogranites); NSL
311
(Nubra-Siachen Leucogranites).
312
313
314
(2)
Fraction codes: Z (zircon); M (monazite); X (xenotime); T (titanite); A (allanite);
R (rutile)
(3)
c=colorless, y=yellow, o=orange/brown, p=pink, op=opaque, tr=translucent,
315
td=turbid, st=slightly turbid, an=anhedral, eu=euhedral, et=euhedral tips, ni=no
316
inclusions, ri=rare inclusions, mi=many inclusions, ab=abraded; pl=pleochroic;
317
number of grains; length of grains (μm).
318
(4)
Masses measured on a Cahn 200 microbalance. Absolute error 0.5-1.0 μg
319
(5)
Radiogenic lead corrected for mass fractionation, laboratory Pb, spike and initial
320
common Pb.
321
(6)
322
(7) 206
323
Total common Pb in analysis.
Pb/204Pb is a measured ratio corrected for mass fractionation and common lead in
the 205Pb/235U spike.
324
(8)
Ratio calculated from 208Pb/206Pb.
325
(9)
Corrected for mass fractionation, laboratory Pb & U spike and initial common Pb
326
(Stacey & Kramers, 1975). Quoted errors are 1σ uncertainty (%).
327
(10)
328
(11) 207
329
Quoted errors are 2σ uncertainty (Ma).
Pb/235U -
206
Pb/238U error correlation coefficient calculated after the method of
Roddick (1987).
330
331
Table S4: U-Pb ID-TIMS data for all data displayed on Concordia diagrams (Figure
332
4). See Table S3 for key.
333
334
Table S5: U-Pb isochron data for Figure 4.
335
(1)
336
337
Rock-type: TDL (Tangtse-Darbuk leucogranites); MMC (Muglib Migmatite
Complex).
(2)
Fraction codes: Z (zircon); T (titanite); A (allanite); F (feldspar).
10
338
(3)
c=colorless, op=opaque, tr=translucent, td=turbid, st=slightly turbid, an=anhedral,
339
ni=no inclusions, ri=rare inclusions, mi=many inclusions, pl=pleochroic; number of
340
grains; length of grains (μm).
341
(4)
Masses measured on a Cahn 200 microbalance. Absolute error 0.5-1.0 μg.
342
(5)
Common lead, blank corrected.
343
(6) 206
344
345
the 205Pb/235U spike.
(7)
346
347
Corrected for mass fractionation, Pb and U blank. Quoted errors are 1σ uncertainty
(%).
(8) 238
348
349
Pb/204Pb is a measured ratio corrected for mass fractionation and common lead in
U/204Pb -
206
Pb/204Pb error correlation coefficient calculated after the method of
Roddick (1987).
(9) 235
350
U/204Pb -
207
Pb/204Pb error correlation coefficient calculated after the method of
Roddick (1987).
351
352
Table S6: U-Pb data obtained via LA-MC-ICP-MS for Pre-collisional magmatism.
353
Data point error ellipses are 2sigma. See Figure 5 and text for details
354
.
355
Table S7: U-Pb data obtained via LA-MC-ICP-MS for Post-collisional magmatism.
356
Data point error ellipses are 2sigma. See Figure 5 and text for details
357
358
Table S8: Summary geochronology for the Karakoram. References in Figure 7.
359
11