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Paleomagnetic and isotopic constrain...

Gilder, Stuart Alan.

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Paleomagnetic and isotopic constraints on the tectonic evolution of south China.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Paleomagnetic and isotopic constraints on the tectonic evolution of south China./
Author:	Gilder, Stuart Alan.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1993,
Description:	126 p.
Notes:	Source: Dissertation Abstracts International, Volume: 55-03, Section: B, page: 7860.
Contained By:	Dissertation Abstracts International55-03B.
Subject:	Geology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9419767

Paleomagnetic and isotopic constraints on the tectonic evolution of south China.
Gilder, Stuart Alan.

Paleomagnetic and isotopic constraints on the tectonic evolution of south China. - Ann Arbor : ProQuest Dissertations & Theses, 1993 - 126 p.

Source: Dissertation Abstracts International, Volume: 55-03, Section: B, page: 7860.

Thesis (Ph.D.)--University of California, Santa Cruz, 1993.

This dissertation reports paleomagnetic and isotopic data that constrain the tectonic development of south China. In Guangxi, Guangdong, and Fujian Province, block rotations of Cretaceous and Tertiary rocks are attributed to the India-Asia collision. The timing and sense of the rotations are consistent with proposed models invoking the extrusion of continental landmasses to the southeast, away from the collision front. In southern Guangxi, Jurassic rocks are rotated counterclockwise (20 $\pm$ 6$\sp\circ$) and displaced northwards (13 $\pm$ 6$\sp\circ$) with respect to coeval rocks from the cratonic interior. In combination with geologic observations, these data support a terrane model based on sinistral shear acting parallel to recognized structural trends. Conversely, Middle Triassic paleomagnetic data from western Guangxi are relatively concordant with respect to those from the cratonic interior. This indicates both places were part of the same tectonic block by that time. With respect to the inland provinces, Early Triassic paleomagnetic results suggest Fujian was either rotated 123 $\pm$ 8$\sp\circ$ counterclockwise and displaced 22 $\pm$ 8$\sp\circ$ northwards, or rotated 57 $\pm$ 8$\sp\circ$ clockwise and displaced 3 $\pm$ 8$\sp\circ$ southwards. The uncertainty in the hemisphere in which the magnetization was acquired make the interpretation of these data non-unique. Sm-Nd and Rb-Sr isotopic mapping helps distinguish between plausible tectonic models. Nd model ages are similar both within proposed tectonic boundaries and across them, and thus are not useful in distinguishing crustal provenances. Therefore, the interpretation that terranes were dissected from a much larger region of similar crust and displaced northward under a sinistral shear regime is the most consistent with the paleomagnetic and isotopic results. In the continental interior, granites possessing anomalously high REE concentrations form a lineament that parallels the trend of two prominent Mesozoic redbed basins. Both the granites and the basins are arguably a part of a continental rift system that lies just inboard of the region most densely intruded by Middle to Late Mesozoic plutons. In combination with the paleomagnetic data, it is proposed that the rift system, delineated by the geochemically anomalous granites, marks the boundary between displaced terranes to the east, and relatively stable cratonic interior to the west.Subjects--Topical Terms:

516570
Geology.

Paleomagnetic and isotopic constraints on the tectonic evolution of south China.
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500 $a Source: Dissertation Abstracts International, Volume: 55-03, Section: B, page: 7860.
502 $a Thesis (Ph.D.)--University of California, Santa Cruz, 1993.
520 $a This dissertation reports paleomagnetic and isotopic data that constrain the tectonic development of south China. In Guangxi, Guangdong, and Fujian Province, block rotations of Cretaceous and Tertiary rocks are attributed to the India-Asia collision. The timing and sense of the rotations are consistent with proposed models invoking the extrusion of continental landmasses to the southeast, away from the collision front. In southern Guangxi, Jurassic rocks are rotated counterclockwise (20 $\pm$ 6$\sp\circ$) and displaced northwards (13 $\pm$ 6$\sp\circ$) with respect to coeval rocks from the cratonic interior. In combination with geologic observations, these data support a terrane model based on sinistral shear acting parallel to recognized structural trends. Conversely, Middle Triassic paleomagnetic data from western Guangxi are relatively concordant with respect to those from the cratonic interior. This indicates both places were part of the same tectonic block by that time. With respect to the inland provinces, Early Triassic paleomagnetic results suggest Fujian was either rotated 123 $\pm$ 8$\sp\circ$ counterclockwise and displaced 22 $\pm$ 8$\sp\circ$ northwards, or rotated 57 $\pm$ 8$\sp\circ$ clockwise and displaced 3 $\pm$ 8$\sp\circ$ southwards. The uncertainty in the hemisphere in which the magnetization was acquired make the interpretation of these data non-unique. Sm-Nd and Rb-Sr isotopic mapping helps distinguish between plausible tectonic models. Nd model ages are similar both within proposed tectonic boundaries and across them, and thus are not useful in distinguishing crustal provenances. Therefore, the interpretation that terranes were dissected from a much larger region of similar crust and displaced northward under a sinistral shear regime is the most consistent with the paleomagnetic and isotopic results. In the continental interior, granites possessing anomalously high REE concentrations form a lineament that parallels the trend of two prominent Mesozoic redbed basins. Both the granites and the basins are arguably a part of a continental rift system that lies just inboard of the region most densely intruded by Middle to Late Mesozoic plutons. In combination with the paleomagnetic data, it is proposed that the rift system, delineated by the geochemically anomalous granites, marks the boundary between displaced terranes to the east, and relatively stable cratonic interior to the west.
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