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Korean Peninsula has continued since ca.
3.6 Ga and culminated at ca. 2.5 and 1.9
- 1.8 Ga. Major age populations of detrital
zircons of the Bansong and Nampo
groups are similar, except for the presence
of Middle-Late Proterozoic ages in
the latter. Inasmuch as these ages are
characteristic for the South China Block,
the Gyeonggi massif, or at least the local
source of the Nampo Group, is most
likely a correlative of the South China
Block.
2010010504
藏 南 康 雄 地 区 中 喜 马 拉 雅 地 块 层 序 构
造 演 化 的 地 质 年 代 学 和 岩 石 学 研 究 =
Geochronological and petrological constraints
for tectonic evolution of the central
Greater Himalayan Sequence in the
Kharta area, southern Tibet. ( 英 文 ). Liu
Y; Siebel W; Massonne H J; Xiao X C.
Journal of Geology, 2007, 115(2): 215-
230
Within the Kharta area, east of Mount
Qomolangma ( Everest), garnet sillimanite
gneisses and granites including
mafic lenses that form the Greater Himalayan
Sequence (GHS) were displaced
beneath the North Col Formation
by the lower South Tibetan Fault (LSTF)
and above the Lesser Himalayan Sequence
by the Main Central Thrust
(MCT). Zircons from mafic lenses,
probably former dikes, were dated by
thermal ionization mass spectrometry to
yield discordant U-Pb results. One sample
gave a discordia line with an upper
intercept age of 971 Ma, suggesting a
late Proterozoic age for emplacement of
the dike. Zircon SHRIMP analyses show
that the garnet sillimanite gneisses and
granites were derived mainly from early
Paleozoic rocks produced by hightemperature
metamorphism and/or partial
melting of Neoproterozoic ( meta)
sedimentary rocks. These crystalline
rocks were buried beneath southern Tibet
and experienced metamorphic conditions
of 750 degrees - 800 degrees C and
14 kbar at Ma. After exhumation they
were trans- 33 +/- 2 formed to lowpressure
rocks at 23 +/- 2 Ma. Structural
analyses have revealed that further exhumation
of the GHS is attributed to the
LSTF and MCT faults beginning at 12 -
13 Ma, according to monazite U-Th-Pb
dating. Finally, these rocks underwent
north-south-trending folding at shallow
depths after 12 Ma.
2010010505
西 班 牙 中 部 地 壳 下 部 麻 粒 岩 捕 掳 体 锆
石 的 U-Pb 研 究 : 伊 利 比 亚 新 元 古 代
到 三 叠 纪 岩 石 圈 演 化 的 记 录 = A U-Pb
study of zircons from a lower crustal
granulite xenolith of the Spanish central
system: A record of Iberian lithospheric
evolution from the Neoproterozoic to the
Triassic. ( 英 文 ). Fernandez-Suarez J;
Arenas R; Jeffries T E; Whitehouse M J;
Villaseca C. Journal of Geology, 2006,
114(4): 471-483
A U-Pb laser ablation inductively
coupled plasma mass spectrometry and
secondary ion mass spectrometry geochronological
study has been performed
on zircons from a felsic granulite xenolith
from the lower crust under the
Variscan belt of Iberia. The ages obtained
reveal zircon-forming events that
span from the late Neoproterozoic
(Cadomian-Avalonian orogeny) to the
early stages of the opening of the Atlantic
Ocean in the Mesozoic, through
Cambro-Ordovician rifting, Devono-
Carboniferous Variscan-Alleghenian
collision, and Permian-Triassic extension
and uplift. The U-Pb age groups
found in zircons from this single lower
crustal xenolith ( ca. 220, 250, 280-310,
460-490, 525, and 550-590 Ma) record
at least one complete cycle of closing
and opening of oceanic basins and collision
of continental masses. Zircons from
the felsic granulite xenolith contain a
synthesis of the geochronological information
found on the surface geology and
record most but not all major lithospheric
events in the region in a ca. 400-
m. yr. period.
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