Dissertation > Excellent graduate degree dissertation topics show

The Geochronology, Geochemical Characteristics and Tectonic Implication of the Xiaomaoling Composite Intrusives in Zhashui, Shaanxi

Author: LiuRenYan
Tutor: RenJiShun；NiuBaoGui
School: Chinese Academy of Geological Sciences
Course: Structural Geology
Keywords: Qinling orogenic belt Little Mao Ling pluton U-Pb zircon dating Hf isotope geochemistry Petrogenesis Geodynamics
CLC: P597.3
Type: Master's thesis
Year: 2011
Downloads: 72
Quote: 0
Read: Download Dissertation

Abstract

Qinling orogenic belt after a long and complex geological evolution, development, multi-stage, multi-stage magmatic intrusions. For each period pluton and its provenance research, helps deepen the geological evolution of the Qinling orogenic understanding of the mechanism. Little Mao Ling pluton is located in the northern margin of the South Qinling, small Mao Ling - steep ridge uplift the western end of the pluton in this paper on the basis of field observations, carried out petrology, zircon U-Pb geochronology, geochemistry and Hf isotope studies, and integrated regional research results, the following understanding: 1 small Mao Ling pluton housing market from the early Song mafic diabase (gabbro) rocks and late scam, grinding grooves Gap and leaves Jiawan Zhong Xing - acidic diorite composition, diorite contains diabase (gabbro) xenoliths. Little Mao Ling duplex rock saw Presinian Mogou Gorge complex xenoliths, and pluton earlier granitic dikes Mogou Gap complex rocks, miscellaneous rocks unconformably covered above Sinian Doushantuo clastic rocks, it should be formed in the composite pluton Presinian Mogou complex rock gorge after Sinian Doushantuo before. 2 by LA-ICP-MS zircon U-Pb geochronology, access to small rock Song Mao Ling duplex housing market emplacement age of 864.4 1.7Ma, scam pluton 846.7 2.7Ma, grinding groove rock gorge body is 859.4 1.7Ma, Ye Jia Wan rock was 861.1 ± 1.8Ma, showed little Mao Ling pluton formed at 870 ~ 840Ma Neoproterozoic. Accordingly, the author of the small Mao Ling pluton is further subdivided into three parts: the early Song housing market hornblende gabbro (gabbro) rock, medium grinding groove Gap quartz diorite - tonalite pluton and leaves Jiawan quartz monzonite - two diorite pluton, late scam diorite - quartz diorite, for the same period ordinal magmatism different product. 3 geochemical analysis shows that small Mao Ling Soong composite pluton early rock and housing market in the late Mogou Gap, leaf bay, rock scam exists between the composition of barriers, are two separate series. Song housing market early rock FeO, K Fe2O3, MgO, TiO2 content is higher, K2O, Na2O content is low, A / CNK = 0.68 ~ 0.83; heavy REE slightly enriched in LREE, with no Eu anomaly or slightly positive Eu anomaly; Rb, Ba, Th, U and other large LILEs low levels, Nb, Ta, Ti, P and other negative anomalies obvious, (Th / Nb) N ratios slightly greater than 1, zr content and Zr / Y ratio is higher, with a continental extensional environment basalts. In the late Mogou Gap, leaves Jiawan and scam diorite potassium, sodium content is high, A / CNK less than 1.1; REE and trace element geochemistry is similar, heavier rare earths LREE enrichment diorite from scam rock - quartz diorite to Mogou Gap quartz diorite - tonalite rocks and then leaves Jiawan quartz monzonite - two diorite, with enhanced acidic rocks, LREE fractionation gradually increased, Eu more and more significant negative anomalies; Mogou Gap, leaves Jiawan and scam rocks are enriched in Rb, Ba, Th, U, K and other large LILE, loss Nb, Ta, Ti, P and other elements, reflects the A typical island arc igneous geochemistry. 4.Hf isotope studies have shown that a small Mao Ling pluton from early to late have different provenance. Early Song housing market altered hornblende gabbro (gabbro) rocks εHf (t) of 7.9 to 9.9, a single-stage model ages of 1107 ~ 1021Ma, may be subject to crustal contamination from depleted mantle source region. Interim grinding groove rock gorge and Ye Jia Wan Hf isotopes similar Mogou Gap pluton εHf (t) is 4.1-5.1, stage model age of 1476 ~ 1427Ma; Ye Jia Wan rock εHf (t) from 3.2 to 5.9 , two-stage model age of 1548 ~ 1371Ma, showed that leaf Jiawan Mogou Gap and mid-Proterozoic rock is formed by mantle-derived substances (juvenile crust) partial melting. Most of the late rock maze zircon εHf (t) is negative (individual points εHf (t) is slightly greater than 0), two-stage model ages between 1970 ~ 1709Ma concentrated in the source region may be ancient Late Paleoproterozoic crust partial melting of mantle mixed with a small amount of proliferation crust. 5 combined with regional geological setting and tectonic evolution of the Qinling orogenic belt, a small Mao Ling pluton early Neoproterozoic after the Qinling orogenic extensional tectonic environment of the rock formation.

Related Dissertations

CLC: > Astronomy,Earth Sciences > Geology > Geochemistry > Isotope geology and geochronology > Geochronology
© 2012 www.DissertationTopic.Net Mobile