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Taiwan Detrital Thermochron 3 (Application 2: Fingerprint provenance…
Taiwan Detrital Thermochron 3
Application 2: Fingerprint provenance
Multiple techniques combined = stronger/better
Petrography
Heavy mineral separates
Isotopic finger printing (Sm-Nd, Rb-Sr)
Fission track dating; Ar-Ar dating (mica)
U-Pb dating
Combined detrital zircon U-Pb & FT
Combined --> provenance interpretation
U-Pb method --> formation age
Fission track --> cooling history
Whereas single method --> ambiguous interpretation
How discern source area ?
Source areas ideally w either:
Diff formation age & same cooling history
Same formation age & diff cooling histories
Source area = area contributing most flux
Hengchun Peninsula Debate
Kirstein 2010
To date -
not affected by arc collision w/Taiwan
Debate whether it represents
Accreted fragment onto Taiwan
Accumulated sediment
(from different source areas)
Loshui & Lilonshan Sediments
Test whether
Same (different) thermochron history ?
∴ Infer same (different) source area
Method
Zr FT & U/Th-He ages
Controversial
Palaeocurrent data for 2 regions = opposed
Whole thing rotated in past or accreted ?
Problem
Only 30 grains - really need > 100
Results Loshui & Lilonshan
Some similarity & some difference in ages
Double date
U/Pb ages differ in 2 regions
FT ages = similar
Peak age population
Different in Mid-Miocene
Interpretation Loshui vs Lilonshan
Crust forming events in SE Asia
--> correspond to diff peak age populations
suggests all samples sourced from SE Asia
Main contributor = SE China
--> both regions have same source ?
U/Pb Age
≈ ZFT Age
∴ Concordant with volcanic source
Similar cooling age --> rapid cooling
Volcanic source ?