## 3 Sampling Strategy, Analytical Methods, and Results
### Petrology and Mineralogical Characteristics  
The Sanggeda mafic intrusion is enriched in large ion lithophile elements (LILEs), such as Rb and Ba, and in high-field-strength elements (HFSEs) like Th, U, and Pb, while being relatively depleted in HFSEs such as Nb, Ta, and Zr [42], a typical characteristic of arc magmas. The fine-grained equigranular (50-100 m in size) gabbro and porphyritic gabbro are relatively fresh. Contacts between them are either sharp or gradual, lacking chilled edges (Figure 2c). The proportion of amphiboles in gabbro varies from 5% to 30%. The gabbro paragenesis consists of plagioclase, amphibole, and clinopyroxene. Most plagioclase has undergone significant saussuritization, leaving only pseudomorphs. Granoblastic hornblendite enclaves (Figure 2d), with grain sizes ranging from 1 mm to 5 mm and some up to 1 cm, are commonly observed in the intrusion. The interstitial material exhibits a cryptocrystalline or microcrystalline texture. Here, we use the term \"phenoxyst\" to describe the crystals dispersed in the matrix of the Sanggeda intrusion, without implying they are in equilibrium with the host magma (see Section 4.1). \"Matrix\" refers the fine-grained material in porphyritic hornblende gabbro. Based on crystal habits, mineral characteristics, and mineral chemistry, the amphibole crystal populations in the intrusion are divided into four categories, referred to as amphibole Types 1-4 (see Table 1 for details). Especially for amphibole Type 2, the mineral chemistry (see the analysis result in the following section) is a key feature distinguishing it from other types. The suffixes P and C denote crystals present as phenocrists and cumulates, respectively. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Rock** & **Mineral Characteristics** & **Habit** & \begin{tabular}{c} **Representative** \\ **Sample Number and** \\ **Photomicrgraphs** \\ \end{tabular} \\ \hline Type 1 & \begin{tabular}{c} Fine-grained \\ hornblende \\ gabbro \\ \end{tabular} & \begin{tabular}{c} About 0.1 mm in size, light green to light \\ brown-yellow with obvious pleochroism, homogeneous composition without growth \\ zoning \\ \end{tabular} & Euhedral & D17-B1-02, Figure 3a \\ \hline Type 2 & \begin{tabular}{c} Porphritic \\ hornblende \\ gabbro \\ \end{tabular} & \begin{tabular}{c} 0.5–3 mm, light green to light brown with \\ obvious pleochroism, interference colors range \\ from second-order blue to blue-green, hexagon, \\ with normal cleavage, partially with embayed \\ outlines, homogeneous but a few with thin \\ growth zoning \\ \end{tabular} & Euhedral/subhedral & D17-B1-01, Figure 3b,e \\ \hline Type 3 & \begin{tabular}{c} 0.5–3 mm, light green to light brown-yellow with \\ obvious pleochroism, interference colors range \\ from second-order blue to blue-green, hexagon, \\ gabbro \\ \end{tabular} & \
\begin{tabular}{c} 0.5–3 mm, light green to light brown-yellow with \\ obvious pleochroism, interference colors range \\ from second-order blue to blue-green, hexagon, \\ with normal cleavage, homogeneous but a few \\ with thin growth zoning \\ \end{tabular} & Euhedral/subhedral & D17-B1-03, Figure 3b,e,f \\ Type 3 &
\begin{tabular}{c} 0.5–3 mm, light green to light brown-yellow with \\ obvious pleochroism, interference colors range \\ from second-order blue to blue-green, hexagon, \\ short cylindrical, with normal cleavage, \\ homogeneous without growth zoning \\ \end{tabular} & Euhedral/subhedral & D17-B2-01, \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Types of amphibole crystal populations. Some clinopyroxene grains in cumulate enclaves (Figure 3d) exhibit a cracked morphology. They are subhedral, with a total volume fraction of approximately 4%, and have sizes similar to amphibole in cumulate, about 1-2 mm.