Table 1 Numerical modelling parameters.

From: Deep mantle anomalies block early Earth melting, challenging a primordial origin

Global parameters72,73

 

Surface temperature

300 K

Mantle thickness

2890 km

Basal layer thickness

200 km

Thermal expansivity

3 × 10− 5 K− 1

Reference strain rate

1 × 10− 15 s− 1

Thermal conductivity

6 W m2 s− 1

Heat capacity

1250 J kg− 1 K− 1

Weighted average half-life

9.22 Gyr

Reference mantle density*

2900 kg m− 3

Basal Layer Reference density*

3500 kg m− 3

Minimum viscosity cut-off

1 × 1020 Pa s

Maximum viscosity cut-off

1 × 1026 Pa s

Compressibility

5.12 × 10− 12 Pa− 1

Viscosity parameters64,67

Upper mantle

Lower mantle

Basal layer**

Dislocation creep

Prefactor (A) Pa− n s− 1

6.51 × 10− 16

6.51 × 10− 16

6 × 10− 24

Stress exponents (n)

3

1+

1+

Activation energy (E) J mol− 1

500 × 103

530 × 103

100 × 103

Activation volume (V) m3 mol− 1

1.3 × 10− 5

1.3 × 10− 5

4 × 10− 7

Diffusion creep

Prefactor (A) Pa− 1 s− 1

6.00 × 10− 17

1.00 × 10− 18

6 × 10− 24

Activation energy (E) J mol− 1

150 × 103

150 × 103

100 × 103

Activation volume (V) m3 mol− 1

6.34 × 10− 7

12.34 × 10− 7

4 × 10− 7

Cohesion(C) MPa

7

 100

Angle of internal friction (φ)

25.434

 30

Phase transitions

660 km

Reference temperature

1900 K

Clapeyron slope

3 MPa K− 1

Parameters varied

 

CMB (Basal) temperature

4500 K, 4800 K, 5500 K

Mantle potential temperature

1430 °C, 1480 °C, 1550 °C, 1630 °C

Radiogenic heating rates

 

Enrichment factor

Mantle heating rate

Basal layer heating rate

\(\:\frac{{H}_{LLVP}}{{H}_{Mantle}}\)=1

3.0942 × 10− 8 W kg− 1

3.0942 × 10− 8 W kg− 1

 

\(\:\frac{{H}_{LLVP}}{{H}_{Mantle}}\)= 5

2.7462 × 10− 8 W kg− 1

1.3731 × 10− 7 W kg− 1

 

\(\:\frac{{H}_{LLVP}}{{H}_{Mantle}}\)= 10

2.4077 × 10− 8 W kg− 1

2.4077 × 10− 7 W kg− 1

 

\(\:\frac{{H}_{LLVP}}{{H}_{Mantle}}\)= 15

2.1435 × 10− 8 W kg− 1

3.2153 × 10− 7 W kg− 1

 

\(\:\frac{{H}_{LLVP}}{{H}_{Mantle}}\)= 20

1.9316 × 10− 8 W kg− 1

3.8632 × 10− 7 W kg− 1

 
  1. *Although the reference (surface) densities differ by more than 4%, compressibility and thermal effects reduce the effective density contrast between the two layers to ~ 4% under modeled P–T conditions.
  2. +Dislocation creep parameters for the lower mantle and basal layer are included as used in the models, even though dislocation creep was neglected (n = 1) in these regions.
  3. **These values are exploratory and are chosen to maintain a viscosity contrast of 200 between the base of the ambient mantle and the top of the basal layer.
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