Fabrics of pre- and syntectonic granite plutons and ... - CPRM

More documents

Recommendations

Info

Granite foliation poles Campina Grande Serra Redonda 48 21 N southern domain S: 88 L: 60 Campina Grande Fig. 6. Drag-fold in banded gneiss hosting a diorite dike. The banded gneiss forms the hanging wall rocks thrusted on porphyritic granite and diorite of the Serra Redonda pluton. The feature suggest the dike crosscut the gneissic banding in the latest ductile stage of the thrust movement. 8 km Serra Redonda pluton Host regional rocks eastern domain porphyritic granite orthogneiss (Early Neoproterozoic) diorite C.J. Archanjo et al. / Journal of Structural Geology 30 (2008) 310e326 MSZ Specimen for zircon U/Pb Shrimp analysis Matinhas shear zone (MSZ) S: 137 L: 104 GSZ NE domain Paleoproterozoic basement S: 129 L: 74 Galante shear zone (GSZ) Fig. 5. Structural map of the Campina Grande Magmatic Complex and country rocks. In the orientation stereograms the foliation pole (S, shaded area) and lineation (L) are shown on Schmidt net (lower hemisphere). Inset: the planar magmatic fabric of Campina Grande and Serra Redonda plutons. MSZ and GSZ correspond to, respectively, the Matinhas and Galante shear zones. S: 177 L: 141 S: 60 L: 44 some of them show a crosscutting relationship with a second, later, magmatic domain. Cores occur in most of the grains. These are rounded in shape; generally, complex internal structures are absent. Radial microfractures from the cores are also present, probably induced by metamictization-related volume expansion of the crystal lattice (e.g. Lee and Tromp, 1995). Fifteen analyses were performed on different zircon grains (Table 1) and plotted on a conventional Wetherill U/Pb Concordia diagram (Fig. 7). Eight analyses are significantly discordant, and were excluded from the age calculation. Two analyses (spots #11, #15) with high 207 *Pb/ 206 *Pb ages, are attributed to inherited, old zircons. The five remaining analyses (spots #1, #3, #4, #5, #6) define a Concordia age of 591 5.3 Ma, the best estimate for crystallization of the Teixeira pluton. Zircons extracted from the Serra Redonda pluton (sample SR1) are prismatic and euhedral, between 200 to 300 mm in length. The color varies from pinkish to light brown. CL images reveal typical magmatic oscillatory zoning. Eighteen zircon grains were dated (see Table 1). Most of the analytical points 315
Table 1 U/Pb SHRIMP isotopic data on zircons from the Teixeira and Serra Redonda granite plutons (NE Brazil) Grain Spot % 206Pbc U ppm Th ppm 232 Th/ 238 U 206 Pb* ppm 206 Pb/ 238 U Age a 207 Pb/ 206 Pb Age a % Discor dant Total 238 U/ 206 Pb % Total 207 Pb/ 206 Pb % 238 U/ 206 Pb a % 207 Pb*/ 206 Pb* a Teixeira 1.1 0.26 695 158 0.24 58.1 596.7 3.9 597 20 0 10.285 0.68 0.06195 0.54 10.312 0.68 0.05983 0.92 0.8 1.1 0.09698 0.68 0.596 2.1 0.52 603 270 0.46 48.7 576.4 3.9 596 25 3 10.637 0.71 0.064 0.58 10.692 0.71 0.05979 1.1 0.771 1.3 0.09353 0.71 0.528 3.1 0.53 832 225 0.28 69.3 593.6 3.9 625 22 5 10.313 0.68 0.0649 0.59 10.367 0.68 0.0606 1 0.806 1.2 0.09646 0.68 0.552 4.1 0.94 837 170 0.21 69.2 587.1 4.6 598 38 2 10.389 0.8 0.06751 0.47 10.488 0.81 0.0599 1.7 0.787 1.9 0.09535 0.81 0.423 5.1 0.61 902 180 0.21 73.7 582.7 4.4 654 21 11 10.507 0.78 0.06634 0.46 10.571 0.78 0.06141 10 0.801 1.3 0.0946 0.78 0.616 6.1 0.20 487 87 0.19 40 587.2 4 599 31 2 10.464 0.7 0.06152 1.2 10.485 0.7 0.05987 1.4 0.787 1.6 0.09537 0.7 0.437 7.1 3.53 1053 787 0.77 85.2 560.6 4.6 576 49 3 10.618 0.82 0.08804 0.67 11.007 0.86 0.0592 2.2 0.742 2.4 0.09085 0.86 0.358 8.1 4.89 1017 502 0.51 81.4 547.7 3.9 523 70 5 10.727 0.67 0.0977 1.1 11.278 0.75 0.0578 3.2 0.707 3.3 0.08867 0.75 0.229 9.1 2.63 1040 800 0.79 70.8 478.9 3.3 536 82 11 12.626 0.67 0.0795 2 12.967 0.71 0.0582 3.8 0.619 3.8 0.07712 0.71 0.186 10.1 2.15 518 152 0.30 38.2 520.9 5.9 623 79 16 11.63 1.1 0.0779 1.9 11.88 1.2 0.0605 3.7 0.702 3.8 0.08416 1.2 0.305 11.1 2.90 926 247 0.28 198 1396.9 9.5 1910 31 27 4.013 0.71 0.1409 0.96 4.133 0.75 0.117 1.8 3.902 1.9 0.242 0.75 0.395 12.1 6.48 1758 977 0.57 128 492.5 5.4 640 320 23 11.78 0.65 0.1134 4.6 12.6 1.1 0.061 15 0.668 15 0.07939 1.1 0.078 13.1 1.49 894 223 0.26 71.9 569 3.7 636 45 11 10.676 0.67 0.07302 1.3 10.837 0.69 0.0609 2.1 0.775 2.2 0.09228 0.69 0.313 14.1 3.82 836 377 0.47 66.9 553.2 3.9 566 57 2 0.14 0.68 0.09013 0.73 11.161 0.73 0.059 2.6 0.729 2.7 0.0896 0.73 0.271 15.1 1.02 522 118 0.23 53 714.1 7.7 1276 86 44 8.449 1.1 0.0915 3.9 8.536 1.1 0.0833 4.4 1.345 4.5 0.1171 1.1 0.252 Serra Redonda 1.1 0.22 408 208 0.53 33.3 584.2 4 578 23 1 10.52 0.72 0.06109 0.71 10.543 0.72 0.0593 1.1 0.7756 1.3 0.09485 0.72 0.565 2.1 0.15 456 251 0.57 36.7 576.6 4 575 20 0 10.671 0.73 0.06046 0.68 10.688 0.73 0.05921 0.91 0.7639 1.2 0.09357 0.73 0.628 3.1 0.19 488 258 0.55 39.1 573.9 3.9 581 22 1 10.721 0.7 0.06092 0.65 10.741 0.71 0.05939 1 0.7624 1.2 0.0931 0.71 0.571 4.1 0.00 438 243 0.57 36.8 601.1 4.2 616 15 2 10.233 0.74 0.06034 0.7 10.233 0.74 0.06034 0.7 0.8131 1 0.09772 0.74 0.724 5.1 0.05 595 412 0.72 47.5 572.3 3.9 591 23 3 10.765 0.7 0.0601 0.98 10.771 0.7 0.05966 1.1 0.7637 1.3 0.09284 0.7 0.554 6.1 0.14 374 194 0.53 30.2 578.6 4 599 20 3 10.635 0.72 0.06101 0.73 10.65 0.72 0.05986 0.93 0.775 1.2 0.0939 0.72 0.616 7.1 1.30 631 334 0.55 50.6 567.6 3.8 570 52 0 10.724 0.68 0.06965 0.99 10.865 0.7 0.0591 2.4 0.75 2.5 0.09204 0.7 0.282 8.1 0.42 535 265 0.51 42.9 572.3 4.9 598 25 4 10.725 0.88 0.06332 0.6 10.771 0.89 0.05986 1.1 0.766 1.4 0.09284 0.89 0.615 9.1 0.22 539 301 0.58 43.7 580.8 3.9 568 21 2 10.583 0.69 0.06086 0.61 10.607 0.7 0.05903 0.94 0.7673 1.2 0.09428 0.7 0.594 10.1 0.34 478 270 0.58 38.5 575.2 3.9 528 28 9 10.678 0.71 0.06076 0.67 10.715 0.71 0.05795 1.3 0.746 1.4 0.09333 0.71 0.492 11.1 0.10 567 296 0.54 45 569 3.9 592 18 4 10.825 0.71 0.06052 0.69 10.837 0.71 0.05968 0.82 0.7593 1.1 0.09228 0.71 0.654 12.1 0.02 491 259 0.54 39.3 573.8 3.8 596 14 4 10.739 0.7 0.05995 0.63 10.741 0.7 0.05979 0.66 0.7675 0.96 0.0931 0.7 0.727 13.1 0.13 522 249 0.49 42.1 577.7 4 597 22 3 10.653 0.71 0.06085 0.62 10.667 0.72 0.05981 1 0.773 1.2 0.09375 0.72 0.581 14.1 0.23 503 267 0.55 41 582.9 4 579 30 1 10.543 0.72 0.0612 1.1 10.568 0.72 0.05933 1.4 0.774 1.5 0.09463 0.72 0.468 15.1 0.14 458 236 0.53 36.5 571.7 4.9 586 24 2 10.768 0.9 0.06067 0.67 10.783 0.9 0.05953 1.1 0.761 1.4 0.09273 0.9 0.631 16.1 0.14 522 275 0.54 41.6 572.1 5.4 596 23 4 10.76 0.98 0.06093 0.63 10.77 0.99 0.05979 1 0.765 1.4 0.09281 0.99 0.687 17.1 0.17 587 353 0.62 45.9 560.6 5.2 582 26 4 10.99 0.96 0.06082 0.6 11.01 0.96 0.05942 1.2 0.744 1.5 0.09085 0.96 0.628 18.1 0.15 462 229 0.51 36.2 562 3.8 584 26 4 10.962 0.71 0.06072 0.98 10.979 0.71 0.05946 1.2 0.747 1.4 0.09109 0.71 0.508 Errors are 1-sigma; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in Standard calibration was 0.23% (not included in above errors but required when comparing data from different mounts). a 204 Common Pb corrected using measured Pb. % 207 Pb*/ 235 U a % 206 Pb*/ 238 U a % err. corr 316 C.J. Archanjo et al. / Journal of Structural Geology 30 (2008) 310e326
Page 1 and 2: Abstract Fabrics of pre- and syntec
Page 3 and 4: 312 C.J. Archanjo et al. / Journal
Page 5: 314 C.J. Archanjo et al. / Journal
Page 17: 326 C.J. Archanjo et al. / Journal

Fabrics of pre- and syntectonic granite plutons and ... - CPRM

Create successful ePaper yourself

Delete template?

Save as template?