Modelos de inteligencia emocional

Burra Group, there may have been transport from Antarctica to the Northern Adelaide Fold Belt through the Southern Adelaide Fold Belt. Goodge et al., (2002) suggested on the basis of ~1400 Ma detrital zircons in the Beardsmore Group of the Transantarctic Mountains, that the trans-Laurentian anorogenic granite belt (Anderson, 1983; Windley, 1993) continued into Antarctica. If this were the case, it would place southwestern United States adjacent to the the Transantarctic Mountains, a distance of some thousands of kilometres from the Willouran Trough (although it would also depend on the orientation of Laurentia relative

to Australia-Antartica) and would likely favour the SWEAT configuration of Rodinia. As

such, it is unlikely that it could have supplied the large (relative to the proximal 1500 – 1750 Ma zircons) proportion of zircons of that age found in the Dome Sandstone.

Detrital zircons from the Skeleton Group (deposited between 1050 – 535 Ma) in southern Victoria Land and the central Trans-Antarctic Mountains are dominated by 1300 Ma to 950 Ma zircons with very few zircons older than 1500 Ma (Wysoczanski and Allibone, 2004). They reject the Rayner Complex as a source for these zircons, instead suggesting that potential Grenville age basement along the margin of eastern Antarctica and eastern Australia was the source of these zircons (Wysoczanski and Allibone, 2004). Their suggestion implies that to the east of the Willouran Trough was a Grenvillean terrane which was rifted away. If this were the case, it may underlie the Lachlan and New England Orogens of eastern Australia as suggested by Direen and Crawford (2003).

4.8

m

.

Minimum detrital zircon ages provide the maximum age of the unit they are within,

and can therefore assist in refining the depositional geochronology. Chapter 2 discussed

the geochronology of the Adelaide Fold Belt, and it is summarized in Figure 4.10. The

minimum detrital zircon U-Pb ages from this study (Table 4.1) do not add significantly to the contentious dates identified in chapter 2, particularly the age from the porphyritic

intrusion in the Skillogalee Dolomite of 797 ± 5 Ma(Drexel, 2009; Reid, 2009). All of the youngest ages from this study are older than the oldest age that has been attributed to the Adelaide Fold Belt rocks, the 827 ± 9 Ma from baddelyite of the Gairdner dyke swarm, which has been correlated with the Wooltana Volcanics (Wingate et al., 1998). Only the Paralana Quartzite lies below the Wooltana Volcanics, and so the youngest zircon from sample PQ1, with an age of 1164 ± 36 Ma provides a maximum age of the onset of deposition of the Adelaide Fold Belt. It is interesting that three samples (DS4, REC1 and

B4) record five zircons from the 850 - 870 Ma period, and it could be speculated that this

may represent volcanism associated with the initial development of the Adelaide Fold Belt, but it is only speculation. No magmatic source of this age is known in Australia but perhaps it has been eroded or lies hidden beneath the Adelaide Fold Belt.

4.9

c

The sources of the detrital zircons can be attributed in the main part to either the Curnamona Province, the Gawler Craton, or the Musgrave Block. Between the ages of about 1500 Ma and 1620 Ma, the zircon ages are not diagnostic of any one source from these three areas.

For zircons younger than about 1350 Ma, the Musgrave Inlier is the most likely source and for those older than about 1750 Ma, the Gawler Craton is the most likely source. There is a group of detrital zircons with ages less than 1000 Ma. These have no source in the area surrounding the Adelaide Fold Belt, but one possibility is that they are derived from the South China Block, which may have been between Australia and Laurentia until about 750 Ma. A second group of detrital zircons, with ages between 1350 and 1450 Ma have two corresponding zircon ages recorded in Australia, on the western margin of the Gawler Craton, but also correspond to the A-type granites in the southwestern United States. The age spectra of sandstones from the Adelaide Fold Belt demonstrate a gradual decrease with time in detrital supply from of the Gawler Craton and the Curnamona Province, and an increasing supply from the Musgrave Block. This trend is apparent throughout the stratal evolution of individual groups but also at the broader stratigraphic scale. The reason for this is likely that within an individual basin phase, with rifting, the adjacent basement was exposed and supplied most of the sediment. With time, the rift phase gave way to the sag phase, subsidence decreased and the rift shoulders become covered with sediments and the topography adjacent to the rift became subdued. At the same time, sediment transport along the rift axis becomes more important in distributing (and redistributing) sediment in the basin and sources sediment from wider areas, resulting in a greater spread of ages with time.

The changes of the detrital zircon spectra from the Curdimurka Subgroup do agree with the model developed for the transition from rift to sag phase. However because it was not

possible to date sufficient zircons from a sample from the Boorloo Siltstone, it wasn’t

tested fully. Therefore the Willouran Trough is interpreted to be a rift basin in the fault linkage stage of development during deposition of the Dome Sandstone.This continued up to deposition of the second sandstone unit of the Recovery Formation (RSds2).

It is concluded that it is unlikely that the Arkaroola area was connected to the Willouran Trough, either during deposition of the Arkaroola Subgroup or the Humanity Seat Formation. The unexpected Musgrave Block age detrital zircon from sample PQ1 is interpreted to suggest it was sourced from a separate area to the Musgrave Block, based on the sample position being one metre above the basement contact. Therefore it is suggested there may have been a Grenvillean age block east of the Curnamona Province which supplied sediment to that area. The detrital zircon age spectra from this study also provide no support for correlating Burra Group rocks with Curdimurka Subgroup rocks, which leads to a rejection of the possibility that the Rook Tuff is a correlative of the Skillogalee Dolomite, based on similar zircin U-Pb ages of volcanics rocks found in both.

The youngest zircon age recorded from the basal Paralana Quartzite is 1164 ± 36 Ma, and this provides an upper limit of the age of the Adelaide Fold Belt. Five zircons from between 850 and 870 Ma from samples DS4, REC1 and B4 are the youngest of all the zircons analysed, but these are all older than, and come from rocks that lie above the Wooltana Volcanics, and so do not provide additional information on the maximum age of the Adelaide Fold Belt.

Chapter 5.

Carbon and oxygen Isotope studIes of the